Question:
Can someone provide me with a schematic to build a power inverter that can change DC to 60hz AC without changing the voltage? It has to be able to handle a maximum of 120VDC on the input. Idealy one that could handle up to a full kilowatt, but even one restricted to as little as 100 watts would prove very useful. Thanks. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> > Can someone provide me with a schematic to build a power inverter > that can change DC to 60hz AC without changing the voltage? It has to be > able to handle a maximum of 120VDC on the input. Idealy one that could > handle up to a full kilowatt, but even one restricted to as little as 100 > watts would prove very useful. > What do you need to power? 120VAC square wave is not the same as 120 VAC > sine wave that ya get out of the wall….. As a matter of fact…. the stuff > that comes out of the wall is 150 volts peak voltage (+ and – peaks > alternating with an RMS power value equivilent to 120VDC).
I put that up as a feeler so I wasn’t very specific. It would be best if it were a sine wave of course to match normal household current. The DC supply will actually be a batter bank with a maximum output of 145.2 Volts DC but of course as characteristic of batteries the voltage will decrease with discharge so 120VDC average. I need the inverter to regulate the power to between 110-120 volts and deliver AC current at 60 hz with something as close to household current as possible. A staircase wave would be an acceptable approximation if it was in reasonably small incriments. I need something that will power standard household items such as a TV set and I’m not sure the tolerances of all those items. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> I have put this out on the net befor….. you might want to consider > using a much lower voltage battery supply since most modern solid state > devices are happier at voltage levels under 100 volts a switching a > much healthier current load. Any how here is my inverter theory, > you can make of it what you want:
This is part of a design for an alternative energy system (wind power). The idea is simple, by keeping the electricity at the same voltage from generation to storage to point of use it avoids the power loss to transformers which can be a considerable percentage. Likewise there is too much line loss in tranmitting low voltage. If we’re going to generate our own power that level of waste is unacceptable. Thanks for the FAQ, I’ll read though it all a bit later. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> If I’m not mistaken, the losses in high-frequency ferrite core > transformers used in inverters and switchers are 1% or so. The majority > of the losses are in the switches (transistors). You’ll have those > losses regardless.
Another chap I’ve discussed alternative energy with before also said the transformers were on the order of 98% efficient. I wonder if the books I was reading are just outdated or if there is some other reson for the discrepency. They sited power losses to transformers on the order of as high as 10-15% > If you are restricted to having your peak output voltage the same as > your input voltage, you’re going to need a 170 volt battery bank. The > peak voltage of a sine wave is sqrt(2) times the RMS voltage. If you > are going to run normal appliances, you need an RMS voltage of 110 to > 120 volts and low harmonic content. This is MUCH easier to do with > electronics regulating the AC voltage and let the battery bank fall > at some convenient (and relatively safe) voltage like 24 or 48.
My original question was for an electronic inverter that would operate at 120 volts. I don’t see as there would be any way to regulate it other than electronically with any level of efficiency. I was just trying to keep the voltage at a constant level throughout the system to avoid wasted power. It is easier with a wind system built from readily available equipment to generate DC than AC. This means that it would require something to regulate the DC voltage down to the voltage of the battery packs at an acceptable efficiency level. Then the batteries would be charged. Then the power would have to be changed to AC and stepped up to the normal 120v houshold level. I worry about the loss in each of these stages. The cumulative loss has to be considered in the sizing of the over all system. > : there is too much line loss in tranmitting low voltage. If we’re going to > : generate our own power that level of waste is unacceptable. > Exactly what were you going to transmit over significant distances? DC > from the source, or AC from the inverter to the point of use?
Line loss is in question to DC from the generator to the batteries and from the batteries to the point of use. If you recall my original post I said that I plan to use 120v DC dirrectly for most applications. The inverters would only be used for a few specific devices that can not be altered to run on DC current. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
Brian, Keep It Simple Stupid. Buy a 12 or 24 volts sine wave inverter and save a bunch on batteries. 120volt DC will kill you if you are not careful. Equipment I refer to is off the shelf. If you need to find a shelf in your area send me an e mail. No one in this group cares about
Response:
>> > Can someone provide me with a schematic to build a power inverter > > that can change DC to 60hz AC without changing the voltage? It has to be > > able to handle a maximum of 120VDC on the input. Idealy one that could > > handle up to a full kilowatt, but even one restricted to as little as 100 > > watts would prove very useful. > What do you need to power? 120VAC square wave is not the same as 120 VAC > sine wave that ya get out of the wall….. As a matter of fact…. the stuff > that comes out of the wall is 150 volts peak voltage (+ and – peaks > alternating with an RMS power value equivilent to 120VDC).
ouch come on now what`s 120 times the square root of two? 170. The peak voltage is 1.4 times the rms. > I put that up as a feeler so I wasn’t very specific. It would be >best if it were a sine wave of course to match normal household current. >The DC supply will actually be a batter bank with a maximum output of >145.2 Volts DC but of course as characteristic of batteries the voltage >will decrease with discharge so 120VDC average. I need the inverter to >regulate the power to between 110-120 volts and deliver AC current at 60 >hz with something as close to household current as possible. A staircase >wave would be an acceptable approximation if it was in reasonably small >incriments. I need something that will power standard household items >such as a TV set and I’m not sure the tolerances of all those items.
you’ll have to flatten out your wave a little to get 120 rms. This could cause problems with things like stereo amplifiers that save the peak voltage. I suppose if you carefully watch the rise and fall rates, you could induce the proper voltages in such systems. Remember, the output of a transformer is almost proportional to the derivative of the input. If you use a square wave, your light bulbs will function, but your stereo will die because the sharp edges of the square wave will induce too high of voltages on the outputs of their transformers. You could just switch your 145 volts one direction through the load and then turn it around in the other direction. Use some lc (inductors and capacitors) stuff to soften the edges. Your reactances will have to change with respect to current flow so that they always act as a proper filter for the resistance of the load. An inductor in series with the current will soften the edges. (it’s just a low pass filter) You’ll have to switch separate inductors in and out of the circuit so that their reactance at say 110 hz is about the same value as the load resistance. You`ll have to be careful switching the inductors in and out because they don`t like to be switched fast unless you switch them exactly when no current is flowing. If you try and switch them fast, they`ll zap your transistors to their doom unless the transistors have large capacitances across them. (bipolar) For small loads you`ll need a large inductance. For large loads, you`ll need a small inductance. Ofcourse, you could use transistors to eat the corners away, but that would mean lots of power loss and expensive transistors. With inductors, your power loss will be minimal. If you raise the frequency of the signal, your inductors can shrink. don`t have a diagram, but that`s how I`d do it in a general description.
Response:
- Hide quoted text — Show quoted text ->> > Can someone provide me with a schematic to build a power inverter >> > that can change DC to 60hz AC without changing the voltage? It has to be >> > able to handle a maximum of 120VDC on the input. Idealy one that could >> > handle up to a full kilowatt, but even one restricted to as little as 100 >> > watts would prove very useful. >> What do you need to power? 120VAC square wave is not the same as 120 VAC >> sine wave that ya get out of the wall….. As a matter of fact…. the stuff >> that comes out of the wall is 150 volts peak voltage (+ and – peaks >> alternating with an RMS power value equivilent to 120VDC). >ouch come on now what`s 120 times the square root of two? 170. The peak >voltage is 1.4 times the rms. > I put that up as a feeler so I wasn’t very specific. It would be >best if it were a sine wave of course to match normal household current. >The DC supply will actually be a batter bank with a maximum output of >145.2 Volts DC but of course as characteristic of batteries the voltage >will decrease with discharge so 120VDC average. I need the inverter to >regulate the power to between 110-120 volts and deliver AC current at 60 >hz with something as close to household current as possible. A staircase >wave would be an acceptable approximation if it was in reasonably small >incriments. I need something that will power standard household items >such as a TV set and I’m not sure the tolerances of all those items. >you’ll have to flatten out your wave a little to get 120 rms. This >could cause problems with things like stereo amplifiers that save the >peak voltage. I suppose if you carefully watch the rise and fall rates, >you could induce the proper voltages in such systems. Remember, the >output of a transformer is almost proportional to the derivative of the >input. If you use a square wave, your light bulbs will function, but your >stereo will die because the sharp edges of the square wave will induce >too high of voltages on the outputs of their transformers. You could just >switch your 145 volts one direction through the load and then turn it >around in the other direction. Use some lc (inductors and capacitors) >stuff to soften the edges. Your reactances will have to change with respect >to current flow so that they always act as a proper filter for the resistance >of the load. An inductor in series with the current will soften the edges. >(it’s just a low pass filter) You’ll have to switch separate inductors in and >out of the circuit so that their reactance at say 110 hz is about the same value >as the load resistance. You`ll have to be careful switching the inductors >in and out because they don`t like to be switched fast unless you switch them >exactly when no current is flowing. If you try and switch them fast, they`ll >zap your transistors to their doom unless the transistors have large capacitances >across them. (bipolar) For small loads you`ll need a large inductance. >For large loads, you`ll need a small inductance. Ofcourse, you could use >transistors to eat the corners away, but that would mean lots of power loss >and expensive transistors. With inductors, your power loss will be minimal. >If you raise the frequency of the signal, your inductors can shrink. >don`t have a diagram, but that`s how I`d do it in a general description.
I designed and built a transformerless inverter several years ago that is as you describe. An article of mine appeared in Home Power Magazine on the subject. The inverter is a simple "H-bridge" using 156 volt nominal rails to produce a low distortion 115 VAC quasi-sine wave output. The waveform is rectangular, switches between three levele: 0 …+156…0…-156… This waveform has approx 7 to 20% total harmonic distortion. I used a total of 20 IRF 640 MOSFETs (200 volt rated, International Rectifier) for an output of 10 KW @ 92% effeciency. This inverter cost about $200 to build. I cancelled my plans to commercially sell this beast when my partner’s attorney recommended against it due to liability concerns of non-isolated power supplies. There are some safety issues with this type inverter that are not easily rectified. 156 volts was selected for rails, requiring 13 twelve, or 26 six volt batteries in series, in order to minimize distortion over the normal range of lead acid batteries. Hope it helps, Gene A. Townsend
Response:
> >>> In article
>>> > Can someone provide me with a schematic to build a power inverter >>> > that can change DC to 60hz AC without changing the voltage? It has to be >>> > able to handle a maximum of 120VDC on the input. Idealy one that could >>> > handle up to a full kilowatt, but even one restricted to as little as 100 >>> > watts would prove very useful.
(Snip) – Hide quoted text — Show quoted text -> I designed and built a transformerless inverter several years ago that > is as you describe. An article of mine appeared in Home Power > Magazine on the subject. > The inverter is a simple "H-bridge" using 156 volt nominal rails to > produce a low distortion 115 VAC quasi-sine wave output. The waveform > is rectangular, switches between three levele: 0 …+156…0…-156… > This waveform has approx 7 to 20% total harmonic distortion. > I used a total of 20 IRF 640 MOSFETs (200 volt rated, International > Rectifier) for an output of 10 KW @ 92% effeciency. This inverter > cost about $200 to build. I cancelled my plans to commercially sell > this beast when my partner’s attorney recommended against it due to > liability concerns of non-isolated power supplies. There are some > safety issues with this type inverter that are not easily rectified. > 156 volts was selected for rails, requiring 13 twelve, or 26 six volt > batteries in series, in order to minimize distortion over the normal > range of lead acid batteries. > Hope it helps, > Gene A. Townsend
I agree with the safety problems with non-isolated supplies. To answer the first question: You should separate this into two problems. 1) charging the batteries. 2) Using the battery output. The first thing you need to decide is what battery voltage you want to use. If you are going to power _only_ an inverter a rough guide would be: 12 volts (6 cells) for a few hundred watts 24 volts (12 cells) for a kilowatt 48 volts (24 cells) for a few kilowatts 130 volts (60 cells) for five -ten kilowatts or so. If you want to power things directly from the batteries (lights and things) then you probably want to go with either 12 volts or 130 volts because of ease of obtaining devices that use these voltages (note that a 130 volt battery bank puts out about 126 to 108 volts, depending on the charge). You can buy inverters off the shelf (or obtain plans) for any of these voltages. The roughly 10% you will lose in an inverter is just the price you must pay. If I was planing to wire my house for DC lighting, I almost certainly would go with a 130 battery bank. You could use the same size wire (#12-14) that you would use for normal AC lights instead of large stuff. Remember, everything must meet the National Electric Code or you will be both in violation of law and unable to get home insurance. Charge the batteries the best way you can. If the power source is a few hundred feet from the batteries, then use the highest voltage you can. However, you _must_ be able to control the charge rate closely if you hope to get any life out of the batteries. By the way, be use to put in a low voltage disconnect on the battery bank set to whatever the battery maker recommends (1.81-1.85 volts per cell is common for the batteries I deal with). You can seriously reduce the life of a battery by discharging it below the design point. Hope this helps.
Response:
> To answer the first question: > You should separate this into two problems. > 1) charging the batteries. > 2) Using the battery output.
This was seperated into two problems. I had only been asking about an inverter to use on the battery output. I just had to go back and explain the charging side because people didn’t think I needed a DC system with this high a voltage. > The first thing you need to decide is what battery voltage you want to use. > If you are going to power _only_ an inverter a rough guide would be: > 12 volts (6 cells) for a few hundred watts > 24 volts (12 cells) for a kilowatt > 48 volts (24 cells) for a few kilowatts > 130 volts (60 cells) for five -ten kilowatts or so.
I had decide on the voltage before I started. I said 120 volt just as an average because that is common household voltage. Five to ten kilowatts is just the range I’ve had in mind all the time. > If you want to power things directly from the batteries (lights and things) > then you probably want to go with either 12 volts or 130 volts because of > ease of obtaining devices that use these voltages (note that a 130 volt > battery bank puts out about 126 to 108 volts, depending on the charge). > You can buy inverters off the shelf (or obtain plans) for any of these > voltages. The roughly 10% you will lose in an inverter is just the price > you must pay. > If I was planing to wire my house for DC lighting, I almost certainly would > go with a 130 battery bank. You could use the same size wire (#12-14) that > you would use for normal AC lights instead of large stuff. Remember, > everything must meet the National Electric Code or you will be both in > violation of law and unable to get home insurance.
This was what I intended all along. I mentioned a 145 volt systems because that would be the maximum voltage of eleven 12 volt battiers in series. As you said as the charge wears down the voltage drops so with this set up I should be able to expect it to deliver a voltage between 120 volts and 145 volts through out the entire usesful portion of the discharge cycle. The higher levels of course can be regulated down to the 120 volt level. When the battery bank drops below 120 volts relays would bring another identical bank that is charged on line in parellel to the first one and once voltage begins flowing from the second bank the first bank will be taken off. It would be less than a second that both banks are connected but this sequence insured uninterupted power. Then the first bank would go into the charge cycle. I have considerable experience with standard 120 volt residential wiring and have had my work pass inspections by professional electricians and city inspectors in three different states. The only difference when I build my own house would be that the source is the DC battery banks instead of AC power from the public utility lines. Most of the equipment will run dirrectly on DC, but there are some things that won’t run on DC so for these I need point of use inverters that I can plug in between the DC wall outlet and the device requiring the AC voltage. For a microwave oven I would need one that will do this while handling up to 1,000 watts. Anything else I can think of will not use more than about 100 watts. I have never seen an off the shelf inverter or plans on how to build one that would take more than 36 volts from the input side. That is what I am looking for and why I originaly posted in here. Can you tell me where I can get plans to build my own inverter for the 130 volt battery source system? I can handle a soldering iron so if I have the plans I don’t think I would have any problem assembling it myself. I have more time than money so I’d rather build my own. > Charge the batteries the best way you can. If the power source is a few > hundred feet from the batteries, then use the highest voltage you can. > However, you _must_ be able to control the charge rate closely if you hope > to get any life out of the batteries.
Charging the batteries is a seperate question that I hadn’t gotten into yet. Unless I can find the 120 volt inverter I will have to completly change the battery bank voltage. The distance between the generator and the battery banks should not be more than 100-200 feet. I’m thinking of using 230 volt DC motors as generators so this would be the voltage in the tranmission lines. The voltage would then have to be regulated down to 150-175 volts for charging the batteries. Assuming you can tell me where to get the plans for the 130 volt inverter than I do need to find plans to build a charger for the system. The source power will be wind generators which will generate DC current so the only thing really need for the charger will be a way to regulate the voltage and a way to check the chrage level on the batteries so it knows when to shut off the charger. The entire system will be controled by a computer. The sensors just need to output results on a five volt signal line for the computer to read and it will trip the appropriate relays. This should keep the electronics fairly simpl as they won’t need to do any sort of decision making. > By the way, be use to put in a low voltage disconnect on the battery bank > set to whatever the battery maker recommends (1.81-1.85 volts per cell is > common for the batteries I deal with). You can seriously reduce the life of > a battery by discharging it below the design point.
Right, as mentioned above a sensor will check voltage levels on the wire from the battery bank to the load. When this voltage level drops below 120 volts the battery bank will be replaced with another fully charged bank. I plan to have three battery banks so there will always be one in use, one charginging, and one in reserve. The batteries will normally charge from a wind system but it also provides for a back up. If the third bank is switched into the load position before the first bank has reached at least half charge the computer will fire up a liquid fueled generator and recharge the second bank from the backup generator just in case the first bank is not fully charged before the third bank reaches cut out voltage level. The liquid fueled generator will actually be an identical generator as the one on the windmills but hooked up to a 4-cycle engine so in all respects the charging will be same. It will just require having a charger between the liquid fueled generator that is identical to the charger in the wind mill connection. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
– Hide quoted text — Show quoted text -> To answer the first question: > You should separate this into two problems. > 1) charging the batteries. > 2) Using the battery output. > This was seperated into two problems. I had only been asking about > an inverter to use on the battery output. I just had to go back and > explain the charging side because people didn’t think I needed a DC system > with this high a voltage. > The first thing you need to decide is what battery voltage you want to use. > If you are going to power _only_ an inverter a rough guide would be: > 12 volts (6 cells) for a few hundred watts > 24 volts (12 cells) for a kilowatt > 48 volts (24 cells) for a few kilowatts > 130 volts (60 cells) for five -ten kilowatts or so. > I had decide on the voltage before I started. I said 120 volt just > as an average because that is common household voltage. Five to ten > kilowatts is just the range I’ve had in mind all the time. > If you want to power things directly from the batteries (lights and things) > then you probably want to go with either 12 volts or 130 volts because of > ease of obtaining devices that use these voltages (note that a 130 volt > battery bank puts out about 126 to 108 volts, depending on the charge). > You can buy inverters off the shelf (or obtain plans) for any of these > voltages. The roughly 10% you will lose in an inverter is just the price > you must pay. > If I was planing to wire my house for DC lighting, I almost certainly would > go with a 130 battery bank. You could use the same size wire (#12-14) that > you would use for normal AC lights instead of large stuff. Remember, > everything must meet the National Electric Code or you will be both in > violation of law and unable to get home insurance. > This was what I intended all along. I mentioned a 145 volt systems > because that would be the maximum voltage of eleven 12 volt battiers in > series. As you said as the charge wears down the voltage drops so with > this set up I should be able to expect it to deliver a voltage between 120 > volts and 145 volts through out the entire usesful portion of the > discharge cycle. The higher levels of course can be regulated down to the > 120 volt level. When the battery bank drops below 120 volts relays would > bring another identical bank that is charged on line in parellel to the > first one and once voltage begins flowing from the second bank the first > bank will be taken off. It would be less than a second that both banks > are connected but this sequence insured uninterupted power. Then the > first bank would go into the charge cycle. > I have considerable experience with standard 120 volt residential > wiring and have had my work pass inspections by professional electricians > and city inspectors in three different states. The only difference when I > build my own house would be that the source is the DC battery banks > instead of AC power from the public utility lines. Most of the equipment > will run dirrectly on DC, but there are some things that won’t run on DC > so for these I need point of use inverters that I can plug in between the > DC wall outlet and the device requiring the AC voltage. For a microwave > oven I would need one that will do this while handling up to 1,000 watts. > Anything else I can think of will not use more than about 100 watts. > I have never seen an off the shelf inverter or plans on how to build > one that would take more than 36 volts from the input side. That is what > I am looking for and why I originaly posted in here. Can you tell me > where I can get plans to build my own inverter for the 130 volt battery > source system? I can handle a soldering iron so if I have the plans I > don’t think I would have any problem assembling it myself. I have more > time than money so I’d rather build my own. > Charge the batteries the best way you can. If the power source is a few > hundred feet from the batteries, then use the highest voltage you can. > However, you _must_ be able to control the charge rate closely if you hope > to get any life out of the batteries. > Charging the batteries is a seperate question that I hadn’t gotten > into yet. Unless I can find the 120 volt inverter I will have to > completly change the battery bank voltage. The distance between the > generator and the battery banks should not be more than 100-200 feet. I’m > thinking of using 230 volt DC motors as generators so this would be the > voltage in the tranmission lines. The voltage would then have to be > regulated down to 150-175 volts for charging the batteries. > Assuming you can tell me where to get the plans for the 130 volt > inverter than I do need to find plans to build a charger for the system. > The source power will be wind generators which will generate DC current so > the only thing really need for the charger will be a way to regulate the > voltage and a way to check the chrage level on the batteries so it knows > when to shut off the charger. The entire system will be controled by a > computer. The sensors just need to output results on a five volt signal > line for the computer to read and it will trip the appropriate relays. > This should keep the electronics fairly simpl as they won’t need to do any > sort of decision making. > By the way, be use to put in a low voltage disconnect on the battery bank > set to whatever the battery maker recommends (1.81-1.85 volts per cell is > common for the batteries I deal with). You can seriously reduce the life of > a battery by discharging it below the design point. > Right, as mentioned above a sensor will check voltage levels on the > wire from the battery bank to the load. When this voltage level drops > below 120 volts the battery bank will be replaced with another fully > charged bank. I plan to have three battery banks so there will always be > one in use, one charginging, and one in reserve. The batteries will > normally charge from a wind system but it also provides for a back up. If > the third bank is switched into the load position before the first bank > has reached at least half charge the computer will fire up a liquid fueled > generator and recharge the second bank from the backup generator just in > case the first bank is not fully charged before the third bank reaches cut > out voltage level. The liquid fueled generator will actually be an > identical generator as the one on the windmills but hooked up to a 4-cycle > engine so in all respects the charging will be same. It will just require > having a charger between the liquid fueled generator that is identical to > the charger in the wind mill connection. > Brian Petroski > Just your stereotypical > polysexual, > bisexual > solitary pagan > from St. Paul, Minnesota
I see that you have put some effort into this. I will look at my office to see if we have plans for a 130 volt inverter, however, I doubt it since we transfer all of that stuff to the client when we complete a job. I can get you a list of suppliers of 130 volt inverters and chargers, but since these are industrial units, it may not be easy to get them to part with plans without buy a unit. Where these are commonly used is in power plants. Most power plants and large substations use a 130 volt battery bank to power their control systems. In some cases, they also have an inverter to give them 120 AC for things that need it. If you have any contacts in the generation side of the power business, you might ask them for help. Another possibly is modifying a lower voltage design. I would guess that the only real difference would be in the voltage ratings of the DC side parts and the turns ratio of the transformer. I think what you are planing to do is a lot more reasonable than many of the plans I see here. Good luck.
Response:
Couple of comments: Some have been writing about great hazards from of 120 VDC. But, this was of course the original Edison system and vestiges of it survived in New York City and maybe elsewhere at least into the 1980’s Shops in Manattan specialized in DC appliances. For all I know this may still be the case and I expect a call to Con Edison would turn it up, along with leads to expertise on the special requirements of DC residential electricity. Switches are an issue; you can buy DC rated wall switches of normal dimensions through ordinary electrical distributors, but switches in lamps and such might want to be changed. I’d be sure to use current limiting fuses between the battery bank(s) and anything else. Also, in older books on DC power systems (DC was widely used on ships) there are some interesting voltage regulation techniques that might have application to your project. Jacobs and others made "110V" wind generators. Exeltech and others can provide 110-120 v inverters. Locating a 110v DC generator should be no great trick either; I see them once in a while. am
Response:
– Hide quoted text — Show quoted text -> Couple of comments: > Some have been writing about great hazards from of 120 VDC. But, > this was of course the original Edison system and vestiges of it survived in > New York City and maybe elsewhere at least into the 1980’s Shops in > Manattan specialized in DC appliances. For all I know this may still > be the case and I expect a call to Con Edison would turn it up, along > with leads to expertise on the special requirements of DC residential > electricity. Switches are an issue; you can buy DC rated wall switches > of normal dimensions through ordinary electrical distributors, but > switches in lamps and such might want to be changed. I’d be sure to > use current limiting fuses between the battery bank(s) and anything else. > Also, in older books on DC power systems (DC was widely used on ships) > there are some interesting voltage regulation techniques that might > have application to your project. > Jacobs and others made "110V" wind generators. Exeltech and others can > provide 110-120 v inverters. Locating a 110v DC generator should be no > great trick either; I see them once in a while.
Thanks for the tips. I’m designing my own wind generator, planning to go with a savonious type because of it’s performance in lower wind speeds. I just need the two key components, the charger and inverter. I have everything else figured out. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> You may find that most devices which run on line current don’t like DC. > Aside from resistance devices (incandescent bulbs, toasters) I can’t > think of anything that does. Not most anything that has either an > electric motor or a power supply. Many if not most demand AC. The > switches on most things would have to be changed in any event, since DC > requires heftier contacts than AC.
The lights go fine off of DC. Electric motors vary, but you can find a lot of equipment with AC/DC motors and it is easy to modify many things like kitchen appliances and power tools. Someone else also mentioned in New York there are still sources of 120 volt DC appliances. These days most equipement DOES run off of DC current. It just tkaes in AC to it’s power supply so it can step down the voltage and then change it to DC. Again an easy modification. Take out the wasteful, heat producting power supply and replace it with a simple voltage divider. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> : When the battery bank drops below 120 volts relays would > : bring another identical bank that is charged on line in parellel to the > : first one and once voltage begins flowing from the second bank the first > : bank will be taken off. It would be less than a second that both banks > : are connected but this sequence insured uninterupted power. Then the > : first bank would go into the charge cycle. > You do not want to do this. Lead-acid batteries prefer shallow > discharges to deep discharges. If you have three banks, one of which is > going to be fully discharged before it is charged, you’ll do two things: > 1.) Guarantee the early failure of your batteries. > 2.) Reduce your total energy storage by up to 1/3.
Lead-acid batteries would not be well suited to this aplication. I hope to locate a good source of gel cells. I also was not going to be "fully discharging" them. I siad the switch would take place when the voltage drop goes below a reasonable level, not when it drops to zero. > I *very* strongly suggest that you read up, see what has been done, and > especially try to find some *failures* to study as well as successes. > You’ll learn more from the failures and it’s much cheaper if it’s not > your own.
I’ve been doing this for the past five years. > : build my own house would be that the source is the DC battery banks > : instead of AC power from the public utility lines. Most of the equipment > : will run dirrectly on DC, but there are some things that won’t run on DC > : so for these I need point of use inverters that I can plug in between the > : DC wall outlet and the device requiring the AC voltage. For a microwave > : oven I would need one that will do this while handling up to 1,000 watts. > : Anything else I can think of will not use more than about 100 watts. > If you are going to need a separate inverter for every AC-only load, and > you need custom-designed inverters to take 120 VDC feed, you’re going to > have a lot of custom hardware floating around. This gets expensive, and > you don’t get a warranty either.
I plan to build them myself so I never expected any warantee, and since I don’t pay labor charges it brings the cost down to less than half. > I suggest using an electric water-heater element as a dump load for > times when the wind has charged the batteries and threatens to boil > them. A fantasy of mine is to use a bank of sodium-vapor lamps as a > dump load; a few KW of them would both light a big room brilliantly and > heat it toastily, allowing one to throw a beach party during a winter > gale. Watch the weather report and keep beer on hand. ;-)
I already have a list of places to dump extra power, including resistance heating elements when all other things are done with and there is still power being produced. > : Assuming you can tell me where to get the plans for the 130 volt > : inverter than I do need to find plans to build a charger for the system. > : The source power will be wind generators which will generate DC current so > : the only thing really need for the charger will be a way to regulate the > : voltage and a way to check the chrage level on the batteries so it knows > : when to shut off the charger. The entire system will be controled by a > : computer. The sensors just need to output results on a five volt signal > : line for the computer to read and it will trip the appropriate relays. > : This should keep the electronics fairly simpl as they won’t need to do any > : sort of decision making. > Are you saying that the complexity is in the software, or there is no > complexity? If the latter, I believe you have no idea what you’re > getting into.
I’m saying that if the devices only have to send a pulse on a signal line they can ve very simple and not require any chips or software of their own. The commputer will handle all the complex parts. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
– Hide quoted text — Show quoted text -> : When the battery bank drops below 120 volts relays would > : bring another identical bank that is charged on line in parellel to the > : first one and once voltage begins flowing from the second bank the first > : bank will be taken off. It would be less than a second that both banks > : are connected but this sequence insured uninterupted power. Then the > : first bank would go into the charge cycle. > You do not want to do this. Lead-acid batteries prefer shallow > discharges to deep discharges. If you have three banks, one of which is > going to be fully discharged before it is charged, you’ll do two things: > 1.) Guarantee the early failure of your batteries. > 2.) Reduce your total energy storage by up to 1/3.
[snip lengthy section] I have a question and maybe an observation – If I understand your system that was described, 11 x 12V batteries, the partially discharged battery bank will still be on line when the fully charged one is connected in parellel with it. Assuming you only discharge to 11V per battery (a rather shallow discharge) the discharged bank would be at 121V. The fully charged bank would be around 13.2V per battery initially or 145V. Would the 24V difference drive a very high current from the charged bank into the partially discharged bank, not unlike when you jump start a dead battery in a car? I know you will only have them connected together for a minute but I think you may have to make and break distressingly high currents since typical lead-acid and gel cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so the surge currrent could be as high as 218 amp. Is this possible?? I may be wrong since most of my knowledge on these types of systems has be gleaned from a variety of sources, some of questionable accuracy. Any comments or critiques would be apprechiated. I hope to learn. > Brian Petroski > Just your stereotypical > polysexual, > bisexual > solitary pagan > from St. Paul, Minnesota
Steve Deutch Usual disclaimer stuff, these are my thoughts and not my boss’es, only for entertainment use by consenting adults, etc.
Response:
> > The lights go fine off of DC. > As long as they’re incandescent, they do. Fluorescents most assuredly > do not, at least not with standard ballasts. > Given what battery storage is going to cost you, why are you even > *thinking* about using incandescent lights? Ponder system cost. > If you cut lighting power demand by 5x, you can cut the size of the > battery bank needed to supply it by 5x also. Run a spreadsheet.
I’m dyslexic, as a result I can’t read or do any type of detail work under florecent lights without getting sever headaches. Also, incandesents run on DC burn brighter than on AC so a 40 watt bulb on DC gives about as much light as a 60-75 watt bulb on AC. Hence you use smaller bulbs and less power. Even if I did bring the lighting requirements alone down I could not downsize the entire system by the same factor as lighting is less than half of the total load. There would be some savings, but not as much as you imply. I have considered all of these things. > Electric motors vary, but you can >find a lot of equipment with AC/DC motors and it is easy to modify many >things like kitchen appliances and power tools. > Yes and no. The speed control in your electric drill is probably based > on a triac, and it won’t work on DC. The vacuum cleaner has a universal > motor, but you’ll need to change the switch. The electric can opener > won’t work, since it has a shaded-pole motor. The turntable won’t work, > neither will the table or ceiling or bathroom fan; the furnace blower > won’t work, the well pump won’t work.
Older equipment tends to have less problems with this than newer stuff. You also generalize way too much. It’s not at all difficult to find ceiling fans, bathroom fans, etc. that will run on DC. You can also find furnace blowers that will but we won’t need one as the house will be heated with passive solar. Haven’t had a working turntable in the house for I don’t know how many years so we won’t miss it, and if you’re having an independant power system then it’s ridiculous to have useless gadgets you don’t need! An electric can opener? Aside from an electric pensil sharpener that is the epitomy of lazyness as far as I’m concerned. It can be done with a manual one in the same amount of time! >These days most equipement DOES run off of DC current. It just tkaes in >AC to it’s power supply so it can step down the voltage and then change >it to DC. Again an easy modification. Take out the wasteful, heat >producting power supply and replace it with a simple voltage divider. > You have a misconception about power supplies. Most power supplies for > computers and such are switchers; they rectify the line current and > filter to get 150-170 volts DC, chop it at high frequency and send it > through a transformer with windings for the various voltages required. > They have DC isolation through the transformer. Old power supplies used > iron transformers working at 60 Hz; you can tell these are no longer in > use, because the modern power supply is only a fraction of the weight of > the old-style transformer alone.
The net effect though is they still make it into low voltage DC for their use. The only computer I have ever seen that used AC power for anything was the Commodore 64/128 line which used the sine wave for a timing signal. I have never seen ANY DOS machine which used anything but 5 volt DC and 12 volt DC coming out of its power supply. > If your generators are providing enough to meet your needs, you don’t > need to cycle the batteries at all; you can just let them float. Your > scheme requires one bank to be discharging whenever there is power > demand, so you are going to have more and deeper cycles than a standard > battery bank design. This is going to reduce your battery life a lot.
This is on the assumption taht the wind will be blowing steady and reliably whenever we happen to need power. Not something I want to depend on. > Okay, fine. Have you seen *any* successful efforts that look even > remotely like what you’re proposing? Any failures, even? Have you > considered why?
*Any* sucessful efforts? When Thomas Edison set up his generator stations most of them worked like this and it powered much of New York for nearly a century. > Remember the 200-watt inverter you saw for sale? I’ll bet that you > couldn’t duplicate it for what it costs retail, because the manufacturer > gets a much better deal on parts than you could. In this, as in many > areas, you are probably better off buying stuff off the shelf.
Not likely. In any product you buy retail usually half the cost is labor. Add into that the cost of executive salaries, advertising, marketing and sales, and I can easily build most of this stuff for half the cost of buying it retail, assuming I can even FIND similar items retail (I haven’t been able to in the five years I’ve been looking). Now on top of that I have no intention of paying retail prices for the components either. There are literally dozens of electronics surplus stores and wholesales with store fronts just here in the Twin Cities metro area alone. Hundreds more that I can get catalogs for mail order. > I’m saying that if the devices only have to send a pulse on a signal >line they can ve very simple and not require any chips or software of >their own. The commputer will handle all the complex parts. > Then you have the problem of managing the complexity in your computer. > How good are you at systems software design for mission-critical > applications, which is what this amounts to? Better not run Windoze.
Get real. All this stuff could be handled by basic programming. No I have no intention of using Windoze, I never use it. For the alternative energy system I don’t even intend to use a DOS machine. Commodore 64s I can pick up for under $10 each will do a wonderful job. It’s the machine I learned machine language programming on by disecting the operating system. I has been my experience that anyone so insistant that a do-it-yourself not attempt a project has been somehow involved in selling a comparable item retail. Doe the idea that I could build this system somehow threaten your much touted degree or job security if it could leak out that it is possible? I’m looking for some explanation of why you so exagerate any tiny point you can find to pick on. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> If I understand your system that was described, 11 x 12V batteries, the partially > discharged battery bank will still be on line when the fully charged one is > connected in parellel with it. Assuming you only discharge to 11V per battery > (a rather shallow discharge) the discharged bank would be at 121V. The fully > charged bank would be around 13.2V per battery initially or 145V. Would the 24V > difference drive a very high current from the charged bank into the partially > discharged bank, not unlike when you jump start a dead battery in a car? I know > you will only have them connected together for a minute but I think you may have > to make and break distressingly high currents since typical lead-acid and gel > cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 > ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so > the surge currrent could be as high as 218 amp. Is this possible??
The second batteries would be brought on line in parellel to the first bank so their amperages would be summed, not the voltages. The voltage while they are both connected would be the average between the two banks; i.e. add them together and divide by two. This will therefor always be less than the voltage of a fully charged battery bank alone. The time the two of these will be switched over is a function of how fast the relays react. The computer will close the relay on the second battery bank and then open the relay on the first bank. This total switiching time will be only a fraction of a second, something on the order of no more than 1/60th of a second I think. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
– Hide quoted text — Show quoted text -> If I understand your system that was described, 11 x 12V batteries, the partially > discharged battery bank will still be on line when the fully charged one is > connected in parellel with it. Assuming you only discharge to 11V per battery > (a rather shallow discharge) the discharged bank would be at 121V. The fully > charged bank would be around 13.2V per battery initially or 145V. Would the 24V > difference drive a very high current from the charged bank into the partially > discharged bank, not unlike when you jump start a dead battery in a car? I know > you will only have them connected together for a minute but I think you may have > to make and break distressingly high currents since typical lead-acid and gel > cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 > ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so > the surge currrent could be as high as 218 amp. Is this possible?? > The second batteries would be brought on line in parellel to the >first bank so their amperages would be summed, not the voltages. The >voltage while they are both connected would be the average between the >two banks; i.e. add them together and divide by two.
Exactly, and that’s the issue. Go back and read the first paragraph again. Overvolting the inverter is not the issue, its the current surge from the charged bank to the discharged bank. The voltages of the banks differ so what you view as a parrallel configuration could also be viewed as a series circuit with a battery of voltage Vcharged – Vdischarged accross the resistance of the discharged bank. As steve mentioned, that resistance is rather low, resulting in a substantial current accross whatever will be doing the switching. If you’ve planned for this, fine, but it sounds like perhaps you may not have. gps
Response:
- Hide quoted text — Show quoted text ->> If I understand your system that was described, 11 x 12V batteries, the partially >> discharged battery bank will still be on line when the fully charged one is >> connected in parellel with it. Assuming you only discharge to 11V per battery >> (a rather shallow discharge) the discharged bank would be at 121V. The fully >> charged bank would be around 13.2V per battery initially or 145V. Would the 24V >> difference drive a very high current from the charged bank into the partially >> discharged bank, not unlike when you jump start a dead battery in a car? I know >> you will only have them connected together for a minute but I think you may have >> to make and break distressingly high currents since typical lead-acid and gel >> cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 >> ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so >> the surge currrent could be as high as 218 amp. Is this possible?? > The second batteries would be brought on line in parellel to the >first bank so their amperages would be summed, not the voltages. The >voltage while they are both connected would be the average between the >two banks; i.e. add them together and divide by two. > Exactly, and that’s the issue. Go back and read the first paragraph > again. Overvolting the inverter is not the issue, its the current > surge from the charged bank to the discharged bank. The voltages of the > banks differ so what you view as a parrallel configuration could also > be viewed as a series circuit with a battery of voltage > Vcharged – Vdischarged accross the resistance of the discharged bank. > As steve mentioned, that resistance is rather low, resulting in a > substantial current accross whatever will be doing the switching. > If you’ve planned for this, fine, but it sounds like perhaps you > may not have. > gps
I think that the battery packs can successfully be paralleled with the addition of power diodes. These diodes are connected so the current from each battery pack can flow only to the load and not to the other pack. This will allow the addition or removal of any battery pack at will. An added benefit is the possible use of battery packs of differing voltage. In this system each battery pack needs to be charged individually as the diodes prevent current from flowing into the batteries. — CUL8ER Stupid is Forever Ignorance can be Fixed Duane C. Johnson Ziggy WA0VBE Red Rock Energy 1825 Florence St. White Bear Lake, MN, USA 55110-3364 (612)635-5065 w (612)426-4766 h http://www.geocities.com/SiliconValley/3027/
Response:
– Hide quoted text — Show quoted text -> If I understand your system that was described, 11 x 12V batteries, the partially > discharged battery bank will still be on line when the fully charged one is > connected in parellel with it. Assuming you only discharge to 11V per battery > (a rather shallow discharge) the discharged bank would be at 121V. The fully > charged bank would be around 13.2V per battery initially or 145V. Would the 24V > difference drive a very high current from the charged bank into the partially > discharged bank, not unlike when you jump start a dead battery in a car? I know > you will only have them connected together for a minute but I think you may have > to make and break distressingly high currents since typical lead-acid and gel > cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 > ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so > the surge currrent could be as high as 218 amp. Is this possible?? > The second batteries would be brought on line in parellel to the >first bank so their amperages would be summed, not the voltages. The >voltage while they are both connected would be the average between the >two banks; i.e. add them together and divide by two.
Exactly, and that’s the issue. Go back and read the first paragraph again. Overvolting the inverter is not the issue, its the current surge from the charged bank to the discharged bank. The voltages of the banks differ so what you view as a parrallel configuration could also be viewed as a series circuit with a battery of voltage Vcharged – Vdischarged accross the resistance of the discharged bank. As steve mentioned, that resistance is rather low, resulting in a substantial current accross whatever will be doing the switching. If you’ve planned for this, fine, but it sounds like perhaps you may not have. gps
Response:
- Hide quoted text — Show quoted text ->> If I understand your system that was described, 11 x 12V batteries, the partially >> discharged battery bank will still be on line when the fully charged one is >> connected in parellel with it. Assuming you only discharge to 11V per battery >> (a rather shallow discharge) the discharged bank would be at 121V. The fully >> charged bank would be around 13.2V per battery initially or 145V. Would the 24V >> difference drive a very high current from the charged bank into the partially >> discharged bank, not unlike when you jump start a dead battery in a car? I know >> you will only have them connected together for a minute but I think you may have >> to make and break distressingly high currents since typical lead-acid and gel >> cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 >> ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so >> the surge currrent could be as high as 218 amp. Is this possible?? > The second batteries would be brought on line in parellel to the >first bank so their amperages would be summed, not the voltages. The >voltage while they are both connected would be the average between the >two banks; i.e. add them together and divide by two. > Exactly, and that’s the issue. Go back and read the first paragraph > again. Overvolting the inverter is not the issue, its the current > surge from the charged bank to the discharged bank. The voltages of the > banks differ so what you view as a parrallel configuration could also > be viewed as a series circuit with a battery of voltage > Vcharged – Vdischarged accross the resistance of the discharged bank. > As steve mentioned, that resistance is rather low, resulting in a > substantial current accross whatever will be doing the switching. > If you’ve planned for this, fine, but it sounds like perhaps you > may not have. > gps
I think that the battery packs can successfully be paralleled with the addition of power diodes. These diodes are connected so the current from each battery pack can flow only to the load and not to the other pack. This will allow the addition or removal of any battery pack at will. An added benefit is the possible use of battery packs of differing voltage. In this system each battery pack needs to be charged individually as the diodes prevent current from flowing into the batteries. — CUL8ER Stupid is Forever Ignorance can be Fixed Duane C. Johnson Ziggy WA0VBE Red Rock Energy 1825 Florence St. White Bear Lake, MN, USA 55110-3364 (612)635-5065 w (612)426-4766 h http://www.geocities.com/SiliconValley/3027/
Response:
> If I understand your system that was described, 11 x 12V batteries, the partially > discharged battery bank will still be on line when the fully charged one is > connected in parellel with it. Assuming you only discharge to 11V per battery > (a rather shallow discharge) the discharged bank would be at 121V. The fully > charged bank would be around 13.2V per battery initially or 145V. Would the 24V > difference drive a very high current from the charged bank into the partially > discharged bank, not unlike when you jump start a dead battery in a car? I know > you will only have them connected together for a minute but I think you may have > to make and break distressingly high currents since typical lead-acid and gel > cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 > ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so > the surge currrent could be as high as 218 amp. Is this possible??
The second batteries would be brought on line in parellel to the first bank so their amperages would be summed, not the voltages. The voltage while they are both connected would be the average between the two banks; i.e. add them together and divide by two. This will therefor always be less than the voltage of a fully charged battery bank alone. The time the two of these will be switched over is a function of how fast the relays react. The computer will close the relay on the second battery bank and then open the relay on the first bank. This total switiching time will be only a fraction of a second, something on the order of no more than 1/60th of a second I think. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> > The lights go fine off of DC. > As long as they’re incandescent, they do. Fluorescents most assuredly > do not, at least not with standard ballasts. > Given what battery storage is going to cost you, why are you even > *thinking* about using incandescent lights? Ponder system cost. > If you cut lighting power demand by 5x, you can cut the size of the > battery bank needed to supply it by 5x also. Run a spreadsheet.
I’m dyslexic, as a result I can’t read or do any type of detail work under florecent lights without getting sever headaches. Also, incandesents run on DC burn brighter than on AC so a 40 watt bulb on DC gives about as much light as a 60-75 watt bulb on AC. Hence you use smaller bulbs and less power. Even if I did bring the lighting requirements alone down I could not downsize the entire system by the same factor as lighting is less than half of the total load. There would be some savings, but not as much as you imply. I have considered all of these things. > Electric motors vary, but you can >find a lot of equipment with AC/DC motors and it is easy to modify many >things like kitchen appliances and power tools. > Yes and no. The speed control in your electric drill is probably based > on a triac, and it won’t work on DC. The vacuum cleaner has a universal > motor, but you’ll need to change the switch. The electric can opener > won’t work, since it has a shaded-pole motor. The turntable won’t work, > neither will the table or ceiling or bathroom fan; the furnace blower > won’t work, the well pump won’t work.
Older equipment tends to have less problems with this than newer stuff. You also generalize way too much. It’s not at all difficult to find ceiling fans, bathroom fans, etc. that will run on DC. You can also find furnace blowers that will but we won’t need one as the house will be heated with passive solar. Haven’t had a working turntable in the house for I don’t know how many years so we won’t miss it, and if you’re having an independant power system then it’s ridiculous to have useless gadgets you don’t need! An electric can opener? Aside from an electric pensil sharpener that is the epitomy of lazyness as far as I’m concerned. It can be done with a manual one in the same amount of time! >These days most equipement DOES run off of DC current. It just tkaes in >AC to it’s power supply so it can step down the voltage and then change >it to DC. Again an easy modification. Take out the wasteful, heat >producting power supply and replace it with a simple voltage divider. > You have a misconception about power supplies. Most power supplies for > computers and such are switchers; they rectify the line current and > filter to get 150-170 volts DC, chop it at high frequency and send it > through a transformer with windings for the various voltages required. > They have DC isolation through the transformer. Old power supplies used > iron transformers working at 60 Hz; you can tell these are no longer in > use, because the modern power supply is only a fraction of the weight of > the old-style transformer alone.
The net effect though is they still make it into low voltage DC for their use. The only computer I have ever seen that used AC power for anything was the Commodore 64/128 line which used the sine wave for a timing signal. I have never seen ANY DOS machine which used anything but 5 volt DC and 12 volt DC coming out of its power supply. > If your generators are providing enough to meet your needs, you don’t > need to cycle the batteries at all; you can just let them float. Your > scheme requires one bank to be discharging whenever there is power > demand, so you are going to have more and deeper cycles than a standard > battery bank design. This is going to reduce your battery life a lot.
This is on the assumption taht the wind will be blowing steady and reliably whenever we happen to need power. Not something I want to depend on. > Okay, fine. Have you seen *any* successful efforts that look even > remotely like what you’re proposing? Any failures, even? Have you > considered why?
*Any* sucessful efforts? When Thomas Edison set up his generator stations most of them worked like this and it powered much of New York for nearly a century. > Remember the 200-watt inverter you saw for sale? I’ll bet that you > couldn’t duplicate it for what it costs retail, because the manufacturer > gets a much better deal on parts than you could. In this, as in many > areas, you are probably better off buying stuff off the shelf.
Not likely. In any product you buy retail usually half the cost is labor. Add into that the cost of executive salaries, advertising, marketing and sales, and I can easily build most of this stuff for half the cost of buying it retail, assuming I can even FIND similar items retail (I haven’t been able to in the five years I’ve been looking). Now on top of that I have no intention of paying retail prices for the components either. There are literally dozens of electronics surplus stores and wholesales with store fronts just here in the Twin Cities metro area alone. Hundreds more that I can get catalogs for mail order. > I’m saying that if the devices only have to send a pulse on a signal >line they can ve very simple and not require any chips or software of >their own. The commputer will handle all the complex parts. > Then you have the problem of managing the complexity in your computer. > How good are you at systems software design for mission-critical > applications, which is what this amounts to? Better not run Windoze.
Get real. All this stuff could be handled by basic programming. No I have no intention of using Windoze, I never use it. For the alternative energy system I don’t even intend to use a DOS machine. Commodore 64s I can pick up for under $10 each will do a wonderful job. It’s the machine I learned machine language programming on by disecting the operating system. I has been my experience that anyone so insistant that a do-it-yourself not attempt a project has been somehow involved in selling a comparable item retail. Doe the idea that I could build this system somehow threaten your much touted degree or job security if it could leak out that it is possible? I’m looking for some explanation of why you so exagerate any tiny point you can find to pick on. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
– Hide quoted text — Show quoted text -> : When the battery bank drops below 120 volts relays would > : bring another identical bank that is charged on line in parellel to the > : first one and once voltage begins flowing from the second bank the first > : bank will be taken off. It would be less than a second that both banks > : are connected but this sequence insured uninterupted power. Then the > : first bank would go into the charge cycle. > You do not want to do this. Lead-acid batteries prefer shallow > discharges to deep discharges. If you have three banks, one of which is > going to be fully discharged before it is charged, you’ll do two things: > 1.) Guarantee the early failure of your batteries. > 2.) Reduce your total energy storage by up to 1/3.
[snip lengthy section] I have a question and maybe an observation – If I understand your system that was described, 11 x 12V batteries, the partially discharged battery bank will still be on line when the fully charged one is connected in parellel with it. Assuming you only discharge to 11V per battery (a rather shallow discharge) the discharged bank would be at 121V. The fully charged bank would be around 13.2V per battery initially or 145V. Would the 24V difference drive a very high current from the charged bank into the partially discharged bank, not unlike when you jump start a dead battery in a car? I know you will only have them connected together for a minute but I think you may have to make and break distressingly high currents since typical lead-acid and gel cell type batteries have internal resistances in the neighborhood of 0.01 to 0.1 ohm. This would imply you are connecting 24V across a load of 0.11 to 1.1 ohm so the surge currrent could be as high as 218 amp. Is this possible?? I may be wrong since most of my knowledge on these types of systems has be gleaned from a variety of sources, some of questionable accuracy. Any comments or critiques would be apprechiated. I hope to learn. > Brian Petroski > Just your stereotypical > polysexual, > bisexual > solitary pagan > from St. Paul, Minnesota
Steve Deutch Usual disclaimer stuff, these are my thoughts and not my boss’es, only for entertainment use by consenting adults, etc.
Response:
> : When the battery bank drops below 120 volts relays would > : bring another identical bank that is charged on line in parellel to the > : first one and once voltage begins flowing from the second bank the first > : bank will be taken off. It would be less than a second that both banks > : are connected but this sequence insured uninterupted power. Then the > : first bank would go into the charge cycle. > You do not want to do this. Lead-acid batteries prefer shallow > discharges to deep discharges. If you have three banks, one of which is > going to be fully discharged before it is charged, you’ll do two things: > 1.) Guarantee the early failure of your batteries. > 2.) Reduce your total energy storage by up to 1/3.
Lead-acid batteries would not be well suited to this aplication. I hope to locate a good source of gel cells. I also was not going to be "fully discharging" them. I siad the switch would take place when the voltage drop goes below a reasonable level, not when it drops to zero. > I *very* strongly suggest that you read up, see what has been done, and > especially try to find some *failures* to study as well as successes. > You’ll learn more from the failures and it’s much cheaper if it’s not > your own.
I’ve been doing this for the past five years. > : build my own house would be that the source is the DC battery banks > : instead of AC power from the public utility lines. Most of the equipment > : will run dirrectly on DC, but there are some things that won’t run on DC > : so for these I need point of use inverters that I can plug in between the > : DC wall outlet and the device requiring the AC voltage. For a microwave > : oven I would need one that will do this while handling up to 1,000 watts. > : Anything else I can think of will not use more than about 100 watts. > If you are going to need a separate inverter for every AC-only load, and > you need custom-designed inverters to take 120 VDC feed, you’re going to > have a lot of custom hardware floating around. This gets expensive, and > you don’t get a warranty either.
I plan to build them myself so I never expected any warantee, and since I don’t pay labor charges it brings the cost down to less than half. > I suggest using an electric water-heater element as a dump load for > times when the wind has charged the batteries and threatens to boil > them. A fantasy of mine is to use a bank of sodium-vapor lamps as a > dump load; a few KW of them would both light a big room brilliantly and > heat it toastily, allowing one to throw a beach party during a winter > gale. Watch the weather report and keep beer on hand. ;-)
I already have a list of places to dump extra power, including resistance heating elements when all other things are done with and there is still power being produced. > : Assuming you can tell me where to get the plans for the 130 volt > : inverter than I do need to find plans to build a charger for the system. > : The source power will be wind generators which will generate DC current so > : the only thing really need for the charger will be a way to regulate the > : voltage and a way to check the chrage level on the batteries so it knows > : when to shut off the charger. The entire system will be controled by a > : computer. The sensors just need to output results on a five volt signal > : line for the computer to read and it will trip the appropriate relays. > : This should keep the electronics fairly simpl as they won’t need to do any > : sort of decision making. > Are you saying that the complexity is in the software, or there is no > complexity? If the latter, I believe you have no idea what you’re > getting into.
I’m saying that if the devices only have to send a pulse on a signal line they can ve very simple and not require any chips or software of their own. The commputer will handle all the complex parts. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> You may find that most devices which run on line current don’t like DC. > Aside from resistance devices (incandescent bulbs, toasters) I can’t > think of anything that does. Not most anything that has either an > electric motor or a power supply. Many if not most demand AC. The > switches on most things would have to be changed in any event, since DC > requires heftier contacts than AC.
The lights go fine off of DC. Electric motors vary, but you can find a lot of equipment with AC/DC motors and it is easy to modify many things like kitchen appliances and power tools. Someone else also mentioned in New York there are still sources of 120 volt DC appliances. These days most equipement DOES run off of DC current. It just tkaes in AC to it’s power supply so it can step down the voltage and then change it to DC. Again an easy modification. Take out the wasteful, heat producting power supply and replace it with a simple voltage divider. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
– Hide quoted text — Show quoted text -> Couple of comments: > Some have been writing about great hazards from of 120 VDC. But, > this was of course the original Edison system and vestiges of it survived in > New York City and maybe elsewhere at least into the 1980’s Shops in > Manattan specialized in DC appliances. For all I know this may still > be the case and I expect a call to Con Edison would turn it up, along > with leads to expertise on the special requirements of DC residential > electricity. Switches are an issue; you can buy DC rated wall switches > of normal dimensions through ordinary electrical distributors, but > switches in lamps and such might want to be changed. I’d be sure to > use current limiting fuses between the battery bank(s) and anything else. > Also, in older books on DC power systems (DC was widely used on ships) > there are some interesting voltage regulation techniques that might > have application to your project. > Jacobs and others made "110V" wind generators. Exeltech and others can > provide 110-120 v inverters. Locating a 110v DC generator should be no > great trick either; I see them once in a while.
Thanks for the tips. I’m designing my own wind generator, planning to go with a savonious type because of it’s performance in lower wind speeds. I just need the two key components, the charger and inverter. I have everything else figured out. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
Couple of comments: Some have been writing about great hazards from of 120 VDC. But, this was of course the original Edison system and vestiges of it survived in New York City and maybe elsewhere at least into the 1980’s Shops in Manattan specialized in DC appliances. For all I know this may still be the case and I expect a call to Con Edison would turn it up, along with leads to expertise on the special requirements of DC residential electricity. Switches are an issue; you can buy DC rated wall switches of normal dimensions through ordinary electrical distributors, but switches in lamps and such might want to be changed. I’d be sure to use current limiting fuses between the battery bank(s) and anything else. Also, in older books on DC power systems (DC was widely used on ships) there are some interesting voltage regulation techniques that might have application to your project. Jacobs and others made "110V" wind generators. Exeltech and others can provide 110-120 v inverters. Locating a 110v DC generator should be no great trick either; I see them once in a while. am
Response:
– Hide quoted text — Show quoted text -> To answer the first question: > You should separate this into two problems. > 1) charging the batteries. > 2) Using the battery output. > This was seperated into two problems. I had only been asking about > an inverter to use on the battery output. I just had to go back and > explain the charging side because people didn’t think I needed a DC system > with this high a voltage. > The first thing you need to decide is what battery voltage you want to use. > If you are going to power _only_ an inverter a rough guide would be: > 12 volts (6 cells) for a few hundred watts > 24 volts (12 cells) for a kilowatt > 48 volts (24 cells) for a few kilowatts > 130 volts (60 cells) for five -ten kilowatts or so. > I had decide on the voltage before I started. I said 120 volt just > as an average because that is common household voltage. Five to ten > kilowatts is just the range I’ve had in mind all the time. > If you want to power things directly from the batteries (lights and things) > then you probably want to go with either 12 volts or 130 volts because of > ease of obtaining devices that use these voltages (note that a 130 volt > battery bank puts out about 126 to 108 volts, depending on the charge). > You can buy inverters off the shelf (or obtain plans) for any of these > voltages. The roughly 10% you will lose in an inverter is just the price > you must pay. > If I was planing to wire my house for DC lighting, I almost certainly would > go with a 130 battery bank. You could use the same size wire (#12-14) that > you would use for normal AC lights instead of large stuff. Remember, > everything must meet the National Electric Code or you will be both in > violation of law and unable to get home insurance. > This was what I intended all along. I mentioned a 145 volt systems > because that would be the maximum voltage of eleven 12 volt battiers in > series. As you said as the charge wears down the voltage drops so with > this set up I should be able to expect it to deliver a voltage between 120 > volts and 145 volts through out the entire usesful portion of the > discharge cycle. The higher levels of course can be regulated down to the > 120 volt level. When the battery bank drops below 120 volts relays would > bring another identical bank that is charged on line in parellel to the > first one and once voltage begins flowing from the second bank the first > bank will be taken off. It would be less than a second that both banks > are connected but this sequence insured uninterupted power. Then the > first bank would go into the charge cycle. > I have considerable experience with standard 120 volt residential > wiring and have had my work pass inspections by professional electricians > and city inspectors in three different states. The only difference when I > build my own house would be that the source is the DC battery banks > instead of AC power from the public utility lines. Most of the equipment > will run dirrectly on DC, but there are some things that won’t run on DC > so for these I need point of use inverters that I can plug in between the > DC wall outlet and the device requiring the AC voltage. For a microwave > oven I would need one that will do this while handling up to 1,000 watts. > Anything else I can think of will not use more than about 100 watts. > I have never seen an off the shelf inverter or plans on how to build > one that would take more than 36 volts from the input side. That is what > I am looking for and why I originaly posted in here. Can you tell me > where I can get plans to build my own inverter for the 130 volt battery > source system? I can handle a soldering iron so if I have the plans I > don’t think I would have any problem assembling it myself. I have more > time than money so I’d rather build my own. > Charge the batteries the best way you can. If the power source is a few > hundred feet from the batteries, then use the highest voltage you can. > However, you _must_ be able to control the charge rate closely if you hope > to get any life out of the batteries. > Charging the batteries is a seperate question that I hadn’t gotten > into yet. Unless I can find the 120 volt inverter I will have to > completly change the battery bank voltage. The distance between the > generator and the battery banks should not be more than 100-200 feet. I’m > thinking of using 230 volt DC motors as generators so this would be the > voltage in the tranmission lines. The voltage would then have to be > regulated down to 150-175 volts for charging the batteries. > Assuming you can tell me where to get the plans for the 130 volt > inverter than I do need to find plans to build a charger for the system. > The source power will be wind generators which will generate DC current so > the only thing really need for the charger will be a way to regulate the > voltage and a way to check the chrage level on the batteries so it knows > when to shut off the charger. The entire system will be controled by a > computer. The sensors just need to output results on a five volt signal > line for the computer to read and it will trip the appropriate relays. > This should keep the electronics fairly simpl as they won’t need to do any > sort of decision making. > By the way, be use to put in a low voltage disconnect on the battery bank > set to whatever the battery maker recommends (1.81-1.85 volts per cell is > common for the batteries I deal with). You can seriously reduce the life of > a battery by discharging it below the design point. > Right, as mentioned above a sensor will check voltage levels on the > wire from the battery bank to the load. When this voltage level drops > below 120 volts the battery bank will be replaced with another fully > charged bank. I plan to have three battery banks so there will always be > one in use, one charginging, and one in reserve. The batteries will > normally charge from a wind system but it also provides for a back up. If > the third bank is switched into the load position before the first bank > has reached at least half charge the computer will fire up a liquid fueled > generator and recharge the second bank from the backup generator just in > case the first bank is not fully charged before the third bank reaches cut > out voltage level. The liquid fueled generator will actually be an > identical generator as the one on the windmills but hooked up to a 4-cycle > engine so in all respects the charging will be same. It will just require > having a charger between the liquid fueled generator that is identical to > the charger in the wind mill connection. > Brian Petroski > Just your stereotypical > polysexual, > bisexual > solitary pagan > from St. Paul, Minnesota
I see that you have put some effort into this. I will look at my office to see if we have plans for a 130 volt inverter, however, I doubt it since we transfer all of that stuff to the client when we complete a job. I can get you a list of suppliers of 130 volt inverters and chargers, but since these are industrial units, it may not be easy to get them to part with plans without buy a unit. Where these are commonly used is in power plants. Most power plants and large substations use a 130 volt battery bank to power their control systems. In some cases, they also have an inverter to give them 120 AC for things that need it. If you have any contacts in the generation side of the power business, you might ask them for help. Another possibly is modifying a lower voltage design. I would guess that the only real difference would be in the voltage ratings of the DC side parts and the turns ratio of the transformer. I think what you are planing to do is a lot more reasonable than many of the plans I see here. Good luck.
Response:
> To answer the first question: > You should separate this into two problems. > 1) charging the batteries. > 2) Using the battery output.
This was seperated into two problems. I had only been asking about an inverter to use on the battery output. I just had to go back and explain the charging side because people didn’t think I needed a DC system with this high a voltage. > The first thing you need to decide is what battery voltage you want to use. > If you are going to power _only_ an inverter a rough guide would be: > 12 volts (6 cells) for a few hundred watts > 24 volts (12 cells) for a kilowatt > 48 volts (24 cells) for a few kilowatts > 130 volts (60 cells) for five -ten kilowatts or so.
I had decide on the voltage before I started. I said 120 volt just as an average because that is common household voltage. Five to ten kilowatts is just the range I’ve had in mind all the time. > If you want to power things directly from the batteries (lights and things) > then you probably want to go with either 12 volts or 130 volts because of > ease of obtaining devices that use these voltages (note that a 130 volt > battery bank puts out about 126 to 108 volts, depending on the charge). > You can buy inverters off the shelf (or obtain plans) for any of these > voltages. The roughly 10% you will lose in an inverter is just the price > you must pay. > If I was planing to wire my house for DC lighting, I almost certainly would > go with a 130 battery bank. You could use the same size wire (#12-14) that > you would use for normal AC lights instead of large stuff. Remember, > everything must meet the National Electric Code or you will be both in > violation of law and unable to get home insurance.
This was what I intended all along. I mentioned a 145 volt systems because that would be the maximum voltage of eleven 12 volt battiers in series. As you said as the charge wears down the voltage drops so with this set up I should be able to expect it to deliver a voltage between 120 volts and 145 volts through out the entire usesful portion of the discharge cycle. The higher levels of course can be regulated down to the 120 volt level. When the battery bank drops below 120 volts relays would bring another identical bank that is charged on line in parellel to the first one and once voltage begins flowing from the second bank the first bank will be taken off. It would be less than a second that both banks are connected but this sequence insured uninterupted power. Then the first bank would go into the charge cycle. I have considerable experience with standard 120 volt residential wiring and have had my work pass inspections by professional electricians and city inspectors in three different states. The only difference when I build my own house would be that the source is the DC battery banks instead of AC power from the public utility lines. Most of the equipment will run dirrectly on DC, but there are some things that won’t run on DC so for these I need point of use inverters that I can plug in between the DC wall outlet and the device requiring the AC voltage. For a microwave oven I would need one that will do this while handling up to 1,000 watts. Anything else I can think of will not use more than about 100 watts. I have never seen an off the shelf inverter or plans on how to build one that would take more than 36 volts from the input side. That is what I am looking for and why I originaly posted in here. Can you tell me where I can get plans to build my own inverter for the 130 volt battery source system? I can handle a soldering iron so if I have the plans I don’t think I would have any problem assembling it myself. I have more time than money so I’d rather build my own. > Charge the batteries the best way you can. If the power source is a few > hundred feet from the batteries, then use the highest voltage you can. > However, you _must_ be able to control the charge rate closely if you hope > to get any life out of the batteries.
Charging the batteries is a seperate question that I hadn’t gotten into yet. Unless I can find the 120 volt inverter I will have to completly change the battery bank voltage. The distance between the generator and the battery banks should not be more than 100-200 feet. I’m thinking of using 230 volt DC motors as generators so this would be the voltage in the tranmission lines. The voltage would then have to be regulated down to 150-175 volts for charging the batteries. Assuming you can tell me where to get the plans for the 130 volt inverter than I do need to find plans to build a charger for the system. The source power will be wind generators which will generate DC current so the only thing really need for the charger will be a way to regulate the voltage and a way to check the chrage level on the batteries so it knows when to shut off the charger. The entire system will be controled by a computer. The sensors just need to output results on a five volt signal line for the computer to read and it will trip the appropriate relays. This should keep the electronics fairly simpl as they won’t need to do any sort of decision making. > By the way, be use to put in a low voltage disconnect on the battery bank > set to whatever the battery maker recommends (1.81-1.85 volts per cell is > common for the batteries I deal with). You can seriously reduce the life of > a battery by discharging it below the design point.
Right, as mentioned above a sensor will check voltage levels on the wire from the battery bank to the load. When this voltage level drops below 120 volts the battery bank will be replaced with another fully charged bank. I plan to have three battery banks so there will always be one in use, one charginging, and one in reserve. The batteries will normally charge from a wind system but it also provides for a back up. If the third bank is switched into the load position before the first bank has reached at least half charge the computer will fire up a liquid fueled generator and recharge the second bank from the backup generator just in case the first bank is not fully charged before the third bank reaches cut out voltage level. The liquid fueled generator will actually be an identical generator as the one on the windmills but hooked up to a 4-cycle engine so in all respects the charging will be same. It will just require having a charger between the liquid fueled generator that is identical to the charger in the wind mill connection. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> >>> In article
>>> > Can someone provide me with a schematic to build a power inverter >>> > that can change DC to 60hz AC without changing the voltage? It has to be >>> > able to handle a maximum of 120VDC on the input. Idealy one that could >>> > handle up to a full kilowatt, but even one restricted to as little as 100 >>> > watts would prove very useful.
(Snip) – Hide quoted text — Show quoted text -> I designed and built a transformerless inverter several years ago that > is as you describe. An article of mine appeared in Home Power > Magazine on the subject. > The inverter is a simple "H-bridge" using 156 volt nominal rails to > produce a low distortion 115 VAC quasi-sine wave output. The waveform > is rectangular, switches between three levele: 0 …+156…0…-156… > This waveform has approx 7 to 20% total harmonic distortion. > I used a total of 20 IRF 640 MOSFETs (200 volt rated, International > Rectifier) for an output of 10 KW @ 92% effeciency. This inverter > cost about $200 to build. I cancelled my plans to commercially sell > this beast when my partner’s attorney recommended against it due to > liability concerns of non-isolated power supplies. There are some > safety issues with this type inverter that are not easily rectified. > 156 volts was selected for rails, requiring 13 twelve, or 26 six volt > batteries in series, in order to minimize distortion over the normal > range of lead acid batteries. > Hope it helps, > Gene A. Townsend
I agree with the safety problems with non-isolated supplies. To answer the first question: You should separate this into two problems. 1) charging the batteries. 2) Using the battery output. The first thing you need to decide is what battery voltage you want to use. If you are going to power _only_ an inverter a rough guide would be: 12 volts (6 cells) for a few hundred watts 24 volts (12 cells) for a kilowatt 48 volts (24 cells) for a few kilowatts 130 volts (60 cells) for five -ten kilowatts or so. If you want to power things directly from the batteries (lights and things) then you probably want to go with either 12 volts or 130 volts because of ease of obtaining devices that use these voltages (note that a 130 volt battery bank puts out about 126 to 108 volts, depending on the charge). You can buy inverters off the shelf (or obtain plans) for any of these voltages. The roughly 10% you will lose in an inverter is just the price you must pay. If I was planing to wire my house for DC lighting, I almost certainly would go with a 130 battery bank. You could use the same size wire (#12-14) that you would use for normal AC lights instead of large stuff. Remember, everything must meet the National Electric Code or you will be both in violation of law and unable to get home insurance. Charge the batteries the best way you can. If the power source is a few hundred feet from the batteries, then use the highest voltage you can. However, you _must_ be able to control the charge rate closely if you hope to get any life out of the batteries. By the way, be use to put in a low voltage disconnect on the battery bank set to whatever the battery maker recommends (1.81-1.85 volts per cell is common for the batteries I deal with). You can seriously reduce the life of a battery by discharging it below the design point. Hope this helps.
Response:
- Hide quoted text — Show quoted text ->> > Can someone provide me with a schematic to build a power inverter >> > that can change DC to 60hz AC without changing the voltage? It has to be >> > able to handle a maximum of 120VDC on the input. Idealy one that could >> > handle up to a full kilowatt, but even one restricted to as little as 100 >> > watts would prove very useful. >> What do you need to power? 120VAC square wave is not the same as 120 VAC >> sine wave that ya get out of the wall….. As a matter of fact…. the stuff >> that comes out of the wall is 150 volts peak voltage (+ and – peaks >> alternating with an RMS power value equivilent to 120VDC). >ouch come on now what`s 120 times the square root of two? 170. The peak >voltage is 1.4 times the rms. > I put that up as a feeler so I wasn’t very specific. It would be >best if it were a sine wave of course to match normal household current. >The DC supply will actually be a batter bank with a maximum output of >145.2 Volts DC but of course as characteristic of batteries the voltage >will decrease with discharge so 120VDC average. I need the inverter to >regulate the power to between 110-120 volts and deliver AC current at 60 >hz with something as close to household current as possible. A staircase >wave would be an acceptable approximation if it was in reasonably small >incriments. I need something that will power standard household items >such as a TV set and I’m not sure the tolerances of all those items. >you’ll have to flatten out your wave a little to get 120 rms. This >could cause problems with things like stereo amplifiers that save the >peak voltage. I suppose if you carefully watch the rise and fall rates, >you could induce the proper voltages in such systems. Remember, the >output of a transformer is almost proportional to the derivative of the >input. If you use a square wave, your light bulbs will function, but your >stereo will die because the sharp edges of the square wave will induce >too high of voltages on the outputs of their transformers. You could just >switch your 145 volts one direction through the load and then turn it >around in the other direction. Use some lc (inductors and capacitors) >stuff to soften the edges. Your reactances will have to change with respect >to current flow so that they always act as a proper filter for the resistance >of the load. An inductor in series with the current will soften the edges. >(it’s just a low pass filter) You’ll have to switch separate inductors in and >out of the circuit so that their reactance at say 110 hz is about the same value >as the load resistance. You`ll have to be careful switching the inductors >in and out because they don`t like to be switched fast unless you switch them >exactly when no current is flowing. If you try and switch them fast, they`ll >zap your transistors to their doom unless the transistors have large capacitances >across them. (bipolar) For small loads you`ll need a large inductance. >For large loads, you`ll need a small inductance. Ofcourse, you could use >transistors to eat the corners away, but that would mean lots of power loss >and expensive transistors. With inductors, your power loss will be minimal. >If you raise the frequency of the signal, your inductors can shrink. >don`t have a diagram, but that`s how I`d do it in a general description.
I designed and built a transformerless inverter several years ago that is as you describe. An article of mine appeared in Home Power Magazine on the subject. The inverter is a simple "H-bridge" using 156 volt nominal rails to produce a low distortion 115 VAC quasi-sine wave output. The waveform is rectangular, switches between three levele: 0 …+156…0…-156… This waveform has approx 7 to 20% total harmonic distortion. I used a total of 20 IRF 640 MOSFETs (200 volt rated, International Rectifier) for an output of 10 KW @ 92% effeciency. This inverter cost about $200 to build. I cancelled my plans to commercially sell this beast when my partner’s attorney recommended against it due to liability concerns of non-isolated power supplies. There are some safety issues with this type inverter that are not easily rectified. 156 volts was selected for rails, requiring 13 twelve, or 26 six volt batteries in series, in order to minimize distortion over the normal range of lead acid batteries. Hope it helps, Gene A. Townsend
Response:
>> > Can someone provide me with a schematic to build a power inverter > > that can change DC to 60hz AC without changing the voltage? It has to be > > able to handle a maximum of 120VDC on the input. Idealy one that could > > handle up to a full kilowatt, but even one restricted to as little as 100 > > watts would prove very useful. > What do you need to power? 120VAC square wave is not the same as 120 VAC > sine wave that ya get out of the wall….. As a matter of fact…. the stuff > that comes out of the wall is 150 volts peak voltage (+ and – peaks > alternating with an RMS power value equivilent to 120VDC).
ouch come on now what`s 120 times the square root of two? 170. The peak voltage is 1.4 times the rms. > I put that up as a feeler so I wasn’t very specific. It would be >best if it were a sine wave of course to match normal household current. >The DC supply will actually be a batter bank with a maximum output of >145.2 Volts DC but of course as characteristic of batteries the voltage >will decrease with discharge so 120VDC average. I need the inverter to >regulate the power to between 110-120 volts and deliver AC current at 60 >hz with something as close to household current as possible. A staircase >wave would be an acceptable approximation if it was in reasonably small >incriments. I need something that will power standard household items >such as a TV set and I’m not sure the tolerances of all those items.
you’ll have to flatten out your wave a little to get 120 rms. This could cause problems with things like stereo amplifiers that save the peak voltage. I suppose if you carefully watch the rise and fall rates, you could induce the proper voltages in such systems. Remember, the output of a transformer is almost proportional to the derivative of the input. If you use a square wave, your light bulbs will function, but your stereo will die because the sharp edges of the square wave will induce too high of voltages on the outputs of their transformers. You could just switch your 145 volts one direction through the load and then turn it around in the other direction. Use some lc (inductors and capacitors) stuff to soften the edges. Your reactances will have to change with respect to current flow so that they always act as a proper filter for the resistance of the load. An inductor in series with the current will soften the edges. (it’s just a low pass filter) You’ll have to switch separate inductors in and out of the circuit so that their reactance at say 110 hz is about the same value as the load resistance. You`ll have to be careful switching the inductors in and out because they don`t like to be switched fast unless you switch them exactly when no current is flowing. If you try and switch them fast, they`ll zap your transistors to their doom unless the transistors have large capacitances across them. (bipolar) For small loads you`ll need a large inductance. For large loads, you`ll need a small inductance. Ofcourse, you could use transistors to eat the corners away, but that would mean lots of power loss and expensive transistors. With inductors, your power loss will be minimal. If you raise the frequency of the signal, your inductors can shrink. don`t have a diagram, but that`s how I`d do it in a general description.
Response:
> If I’m not mistaken, the losses in high-frequency ferrite core > transformers used in inverters and switchers are 1% or so. The majority > of the losses are in the switches (transistors). You’ll have those > losses regardless.
Another chap I’ve discussed alternative energy with before also said the transformers were on the order of 98% efficient. I wonder if the books I was reading are just outdated or if there is some other reson for the discrepency. They sited power losses to transformers on the order of as high as 10-15% > If you are restricted to having your peak output voltage the same as > your input voltage, you’re going to need a 170 volt battery bank. The > peak voltage of a sine wave is sqrt(2) times the RMS voltage. If you > are going to run normal appliances, you need an RMS voltage of 110 to > 120 volts and low harmonic content. This is MUCH easier to do with > electronics regulating the AC voltage and let the battery bank fall > at some convenient (and relatively safe) voltage like 24 or 48.
My original question was for an electronic inverter that would operate at 120 volts. I don’t see as there would be any way to regulate it other than electronically with any level of efficiency. I was just trying to keep the voltage at a constant level throughout the system to avoid wasted power. It is easier with a wind system built from readily available equipment to generate DC than AC. This means that it would require something to regulate the DC voltage down to the voltage of the battery packs at an acceptable efficiency level. Then the batteries would be charged. Then the power would have to be changed to AC and stepped up to the normal 120v houshold level. I worry about the loss in each of these stages. The cumulative loss has to be considered in the sizing of the over all system. > : there is too much line loss in tranmitting low voltage. If we’re going to > : generate our own power that level of waste is unacceptable. > Exactly what were you going to transmit over significant distances? DC > from the source, or AC from the inverter to the point of use?
Line loss is in question to DC from the generator to the batteries and from the batteries to the point of use. If you recall my original post I said that I plan to use 120v DC dirrectly for most applications. The inverters would only be used for a few specific devices that can not be altered to run on DC current. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> > Can someone provide me with a schematic to build a power inverter > that can change DC to 60hz AC without changing the voltage? It has to be > able to handle a maximum of 120VDC on the input. Idealy one that could > handle up to a full kilowatt, but even one restricted to as little as 100 > watts would prove very useful. > What do you need to power? 120VAC square wave is not the same as 120 VAC > sine wave that ya get out of the wall….. As a matter of fact…. the stuff > that comes out of the wall is 150 volts peak voltage (+ and – peaks > alternating with an RMS power value equivilent to 120VDC).
I put that up as a feeler so I wasn’t very specific. It would be best if it were a sine wave of course to match normal household current. The DC supply will actually be a batter bank with a maximum output of 145.2 Volts DC but of course as characteristic of batteries the voltage will decrease with discharge so 120VDC average. I need the inverter to regulate the power to between 110-120 volts and deliver AC current at 60 hz with something as close to household current as possible. A staircase wave would be an acceptable approximation if it was in reasonably small incriments. I need something that will power standard household items such as a TV set and I’m not sure the tolerances of all those items. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> I have put this out on the net befor….. you might want to consider > using a much lower voltage battery supply since most modern solid state > devices are happier at voltage levels under 100 volts a switching a > much healthier current load. Any how here is my inverter theory, > you can make of it what you want:
This is part of a design for an alternative energy system (wind power). The idea is simple, by keeping the electricity at the same voltage from generation to storage to point of use it avoids the power loss to transformers which can be a considerable percentage. Likewise there is too much line loss in tranmitting low voltage. If we’re going to generate our own power that level of waste is unacceptable. Thanks for the FAQ, I’ll read though it all a bit later. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
Can someone provide me with a schematic to build a power inverter that can change DC to 60hz AC without changing the voltage? It has to be able to handle a maximum of 120VDC on the input. Idealy one that could handle up to a full kilowatt, but even one restricted to as little as 100 watts would prove very useful. Thanks. Brian Petroski Just your stereotypical polysexual, bisexual solitary pagan from St. Paul, Minnesota
Response:
> www.bibby-sterilin.co.uk/cat/azlon/ptfe.htm > www.redwood-plastics.com/datasheets/teflon.html > www.ddc.com/~kjohnson/safety.htm > www.petbirdreport.com/dangers.shtml > www.OldWorldAviaries.com/text/styles/teflon.html > www.theaviary.com/teflon.shtml > www.osha-slc.gov./ChemSamp_data/CH_263700.html > > Cool > > Bob w > > >Bob, > > >I’ll dig thru my bookmarks and I’ll send it to ya. > > >Marco > > >> I would like to read that report Marco. > > >> Bob W > > >> >You DO NOT have to ‘incinerate’ the pot for it to be dangerous > > >> for your > > >> >birds. I also read a report that mentioned that non stick coatings > > >> >(such as teflon) can emit toxic fumes at much lower temperatures > > >> than > > >> >previously reported. > > >> >Marco > > >> >> It only dangerous if you let it burn.People who know how to cook > > >> >> use low to > > >> >> medium heat,people who dont use incinerate and walk away.And I > > >> own > > >> >> one pot > > >> >> coated with Teflon two quart size.The rest are stainless > > >> >> revere ware. Alf > > >> >* Sent from RemarQ http://www.remarq.com The Internet’s > > >> Discussion Network > > >> * > > >> >The fastest and easiest way to search and participate in Usenet – > > >> Free! > > >* Sent from RemarQ http://www.remarq.com The Internet’s Discussion > Network > > * > > >The fastest and easiest way to search and participate in Usenet – Free! 
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). Donald Borowski WA6OMI Hewlett-Packard, Spokane Division "Angels are able to fly because they take themselves so lightly." -G.K. Chesterton 