Question:
In article <, I have reciently been told that the TRACE Sine Wave model SW4024 is a true sine wave and not an approximation like the lower end TRACE DR2424. Is this true ? What are the facts around this ?
The waveform from the SW4024 approximates a sine wave with what Home Power Magazine calls a "Mayan temple" waveform. The 4024 uses between 34 and 52 steps per cycle depending on battery voltage and/or load. I upgraded to the 4024 from a 2624, and the difference is astonishing. Electric motors start more easily and have more power. There are no squiggly lines in the TV, and the inverter noise in my stereo system is so low that I can only hear it when no audio signal is present. It has no problem with loads in my house like the dishwasher, washing machine, and even the submersible cistern pump. It also automatically starts my back-up generator when needed and diverts the wind power to an alternative load when the battery is full. The Trace SW4024 is quite simply, IMHO, the best inverter ever made. — John A. Stanley
Response:
Questions: 1) What shuts the backup generator off again ? Is this a programmable time interval or other arrangement ? 2) What are you using for an alternative load ? Water heater perhaps ?
Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste! 3) Does the startup/shutdown of the generator create any noticeable glitches or voltage fluctuations ? The Trace SW4024 is quite simply, IMHO, the best inverter ever made. Sounds tempting
My wind & solar power system (currently under design, hopefully implemented next year when I move house) doesn’t require an inverter. It seems such a waste of money to store electricity in 12V or 24V batteries and then have to run it through an inverter to convert 12/24-110 (or in my case 230VAC). My system uses a rewound alternator which gives me 200VDC which I use to charge a bank of 13 12V batteries wired in *series* such that I have about 180Volts on tap. That 180VDC is then reticulated throughout the house and at each power-point there is a small FET-bridge which acts as a pulse-width modulator to give me a very accurate 230VAC sine-wave output. By doing things this way you get the following benefits: 1. Lighter wiring can be used from the generator and the batteries since I2R losses are dramatically reduced thanks to the much lower currents. 2. No inverter is required, just a simple FET bridge and driver circuit. 3. Much higher powered appliances can be run without the need for a huge inverter which would most likely lose significant efficiency under light loads. 4. Since the FET bridges are so simple and cheap to produce, and since you have multiple units around the house you’re not going to be adversely affected by a failure in the way that you would if you were using a single inverter to run all your appliances. 5. The FET bridge can be designed to operate at quite high pulse-rates (5Khz+) which makes filtering the output wave very easy with the result that RFI is significantly reduced. I was thinking of going commercial with these things if there was enough interest. *=[FREE FAX GATEWAY INTO THE AUCKLAND, NZ TOLL-FREE AREA]=* * sponsored by FaxMail Technologies * * Send email to for details * *=========================================================*
Response:
In article <, 2) What are you using for an alternative load ? Water heater perhaps ? Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste!
The electricity gets diverted to heating water only when the battery bank is full. Wind turbines must always see a load otherwise they fly apart, so when the battery can no longer be the load the power must be diverted to an alternative load such as a water heater. If you were suggesting that the alternative load should be a heat pump instead of resistance heaters, I can guarantee that it wouldn’t work because when the wind power is diverted from the battery the battery voltage drops. When it drops the relay lets the wind power flow to the battery again. When the battery is full that relay cycles on and off every few seconds, sending intermittant pulses of power to the diversionary load, and if the load were a motor running a compressor it would likely destroy the compressor. And even if one were to program some hysteresis into the relay’s set point (which the Trace can do), the cycling times would still very likely be too short to safely run a compressor. — John A. Stanley
Response:
In article <, In article <, I upgraded to the 4024 from a 2624, ……… ……………………. It also automatically starts my back-up generator when needed and diverts the wind power to an alternative load when the battery is full. Questions: 1) What shuts the backup generator off again ? Is this a programmable time interval or other arrangement ?
There is one relay that activates the genset’s ignition and one relay that activates the starter motor. I set mine to come on when battery voltage drops to a certain voltage for ten minutes (that eliminates genset starting when there is a voltage drop from a large load’s initial surge.) You can also program quiet times when the genset won’t come on unless the volatge drops to an even lower voltage. 2) What are you using for an alternative load ? Water heater perhaps ?
My wind energy comes to the house as 240 volt 3-phase AC where it is stepped down and rectified. When the battery is full, the Trace activates a relay that sends the 240vac to three electric hot water elements in the solar thermal storage tank. 3) Does the startup/shutdown of the generator create any noticeable glitches or voltage fluctuations ?
When the Trace transfers the house over to genset power and starts charging the batteries there is a small glitch that results in a small flicker of the lights. I have not experienced any problems with electronics from the glitch. — John A. Stanley
Response:
In article <, Questions: 2) What are you using for an alternative load ? Water heater perhaps ? Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste!
The question referred to excess electricity produced when the batteries were in a state of full charge. (This is assuming that somewhere on the planet there may be an alternative energy household with a surplus of energy). If not water heating, then what ? Pumping ? While I completely agree that water heating is not a good primary use for self-generated electric, seems as though an electrical pre-heat tank for surplus electricity feeding to a tankless propane unit would be a reasonable load management trick. My system uses a rewound alternator which gives me 200VDC which I use to charge a bank of 13 12V batteries wired in *series* such that I have about 180Volts on tap. That 180VDC is then reticulated throughout the house and at each power-point there is a small FET-bridge which acts as a pulse-width modulator to give me a very accurate 230VAC sine-wave output.
This is certainly an interesting idea, although I would think it might have the following drawbacks: 1) For a PV charged system, there is the question of how to add incremental charging. The need to purchase 12 v. PV modules in 15 panel increments would seem to be a substantial problem. 2) To my mind, high voltage DC seems to have some safety issues. (Arcing, need for special switches, etc.). I have also heard it asserted that AC "lets go of you" more readily than DC, should you complete a circuit with your hands. 3) Each FET-bridge would have to be sized for max load, and would have to have a safe failure mode. Possible "cross-talk" problems as well ? 4) Inverter efficiency is steadily increasing, and best of my recollection can stay above 90 % through most of the load range. Is there a real advantage to be had here ? These are questions of genuine interest, and in no way intended as flames. Looking forward to your response. Rob Kleinschmidt *=[FREE FAX GATEWAY INTO THE AUCKLAND, NZ TOLL-FREE AREA]=* * sponsored by FaxMail Technologies * * Send email to for details * *=========================================================*
Response:
: In article <, : : 2) What are you using for an alternative load ? Water : heater perhaps ? : : Gasp! Nobody using solar, wind or other low-output electrical generation : should be using a water heater unless it’s a heat-pump. Heating water with : valuable electricity is such a waste! : : The electricity gets diverted to heating water only when the : battery bank is full. Wind turbines must always see a load : otherwise they fly apart, so when the battery can no longer be : the load the power must be diverted to an alternative load such : as a water heater. : : If you were suggesting that the alternative load should be a : heat pump instead of resistance heaters, I can guarantee that it : wouldn’t work because when the wind power is diverted from the : battery the battery voltage drops. When it drops the relay lets : the wind power flow to the battery again. When the battery is : full that relay cycles on and off every few seconds, sending : intermittant pulses of power to the diversionary load, and if : the load were a motor running a compressor it would likely : destroy the compressor. And even if one were to program some : hysteresis into the relay’s set point (which the Trace can do), : the cycling times would still very likely be too short to safely : run a compressor. The simple answer to this is to put the compressor in the system as a regular load just like anything else and switch it on to generate a load. It shouldn’t need to be an either/or situation of batt or excess load. You could use a compressor with a DC motor and Pulse-width-modulate the DC direct from the charging system to get a variable speed compressor to allow you to keep a constant system load and keep the turbine running at optimum speed and efficiency. Marc Christensen
Response:
The question referred to excess electricity produced when the batteries were in a state of full charge. (This is assuming that somewhere on the planet there may be an alternative energy household with a surplus of energy). If not water heating, then what ? Pumping ?
I’ve actually wondered about this myself. There have been lots of "ideas" for storing excess energy in situations like this but most of them (huge basment flywheels, pumping water into a tower, etc) tend to be fairly impractical for the average home user. About the best idea I can come up with is using it to heat a 5000 gallon tank of water which has been insulated and buried underground. The heat thus stored could be used during the winter months for internal heating through radiators or via heat-exchangers and ducted airflows. Even in this situation I’d still opt for a heat-pump in preference to a resistive immersion heater. The differences in efficiency are *huge*. My system uses a rewound alternator which gives me 200VDC which I use to charge a bank of 13 12V batteries wired in *series* such that I have about 180Volts on tap. That 180VDC is then reticulated throughout the house and at each power-point there is a small FET-bridge which acts as a pulse-width modulator to give me a very accurate 230VAC sine-wave output. This is certainly an interesting idea, although I would think it might have the following drawbacks: 1) For a PV charged system, there is the question of how to add incremental charging. The need to purchase 12 v. PV modules in 15 panel increments would seem to be a substantial problem.
Maximum PV charging currents are significantly less than maximum load currents so there’s no reason why you can’t use existing 12V/24V PV arrays and run them through an inverter and rectifier to create the 120V charging voltage. I2R losses are much lower on this side of the equation and you can use a *much* smaller (cheaper/simpler) inverter for this purpose. 2) To my mind, high voltage DC seems to have some safety issues. (Arcing, need for special switches, etc.). I have also heard it asserted that AC "lets go of you" more readily than DC, should you complete a circuit with your hands.
There is nowhere that you need to switch the DC voltages (using a switch or relay) regularly. The Fet bridge uses (passes) no current when there’s no load and so the switch can be on the AC side. In this situation it’s exactly the same as switching normal 110VAC. As regards to the safety issues of DC vs AC, I’ve read nothing to substantiate the "belief" that AC "lets go of you". If you examine the situation: at 50Hz there are two zero-voltage points and two periods when the voltage is "safe", say 50V or less. Assuming that these two "safe" periods account for 50% of the cycle we then find that the length of such a "safe" period is around 20mS. I don’t think that your muscles could relax quickly enough to let go of anything "live" that you might have grabbed ahold of. The other consideration is that the DC wiring should not be in a location where it can be inadvertantly touched and all maintenance should be performed *only* after disconnecting the batteries from the wiring by use of a master switch. 3) Each FET-bridge would have to be sized for max load, and would have to have a safe failure mode. Possible "cross-talk" problems as well ?
The FETs in a FET-bridge are only carrying 1/10th to 1/5th the current of the switching transistors in a 12/24V to 110VAC inverter and whereas an inverter may need to supply several outlets, each outlet can have its own FET-bridge thus reducing the maximum loading per unit. The safe failure-mode is very easy to arrange. There is a over-current fuse on the DC side to protect against both FETs on one side of the bridge going short-circuit. The output of the bridge is also monitored by a simple circuit which immediately detects any open-circuit or drive-circuitry failures and reacts to instantly shut the bridge down. 4) Inverter efficiency is steadily increasing, and best of my recollection can stay above 90 % through most of the load range. Is there a real advantage to be had here ?
Yes, the advantages include: - increased redundancy. Instead of all AC outlets being dependent on a single inverter, each outlet has its own FET-bridge. The failure of one bridge still leaves all other outlets fully operative. – simplicity. Good sine-wave inverters are complex and expensive, FET bridges are by comparison very simple and cheap. – efficiency. If your inverter is located close to your batteries then I2R losses won’t be significant but what about your generation facilities? This is especially true if you run a wind-generator which is frequently located some distance (ie: more than 20 yards) away. If your generator puts out 20A or more at 12V/24V (240-480 Watts+) then I2R losses can become significant (even .01 ohms of line resistance wastes 16 watts when it’s carrying 40A) – mandating the use of heavier (more expensive) cabling. If you increase the voltage by a factor of five then you reduce the current by a factor of five which reduces I2R losses by a factor of 25. This is the very reason that the national power grid runs voltages of over 100KV, to keep I2R losses to an absolute minimum. These are questions of genuine interest, and in no way intended as flames. Looking forward to your response.
Fair enough. I’m not someone who likes wasting money (hence the desire to be energy self sufficient) so I’ve weighed up the pro’s and con’s very carefully before committing to this project. The main benefits to me are: * simplicity. A FET bridge requires just a handful of components and eliminates the need for special transformers, large cases and high current devices. Anyone who has basic soldering abilities and can read will be able to assemble a FET-bridge in kitset form. * efficiency. A FET bridge based system will always be more efficient than an inverter because it reduces I2R losses. * cost. A FET bridge-based system is highly scalar. You can just keep adding bridges as you add appliances or as you build your house. The entry-level cost for a FET bridge system is significantly lower than that of an inverter-based system. * reliability. *good* inverters are sufficiently expensive that not everyone can afford to have a standby unit available. I like the prospect of multiple redundancy that guarantees I’ll never be left without power just because one $0.10 component has failed. Thanks to their low-cost I can afford to keep a couple of spare FET bridges lying around "just in case". I hope that answers your queries. *==[FREE-FAX GATEWAY INTO THE AUCKLAND NZ TOLL-FREE AREA]==* * FREE listings in NZ’s largest WWW Business Directory * * http://www.actrix.gen.nz/biz/faxmail/faxmail.htm * *==========================================================*
Response:
The electricity gets diverted to heating water only when the battery bank is full. Wind turbines must always see a load otherwise they fly apart, so when the battery can no longer be the load the power must be diverted to an alternative load such as a water heater.
Good grief what kind of wind generator are you using? A "good" wind generator will have a variable pitch propeller, the pitch of which can be either mechanically controlled by a centrifugal mechanism or (in the case of a more sophisticated unit) by a microprocessor and small servomechanisms. Such a system not only ensures that the generator won’t over-rev but also enables optimal efficiency over a wider range of wind speeds (including very light winds) where fixed-pitch vanes are often almost fully stalled and very inefficient — just when you need maximum efficiency. If you were suggesting that the alternative load should be a heat pump instead of resistance heaters, I can guarantee that it wouldn’t work because when the wind power is diverted from the battery the battery voltage drops. When it drops the relay lets the wind power flow to the battery again. When the battery is full that relay cycles on and off every few seconds, sending intermittant pulses of power to the diversionary load, and if the load were a motor running a compressor it would likely destroy the compressor. And even if one were to program some hysteresis into the relay’s set point (which the Trace can do), the cycling times would still very likely be too short to safely run a compressor.
Switching the load on the basis of floating battery voltage is not a particularly good way to manage your energy resources. It is far smarter to measure the energy being generated, subtract the energy being used and ad a margin for battery efficiency before determining the excess. A simple single-chip microprocessor and interface circuitry can achieve this quite simply. *==[FREE-FAX GATEWAY INTO THE AUCKLAND NZ TOLL-FREE AREA]==* * FREE listings in NZ’s largest WWW Business Directory * * http://www.actrix.gen.nz/biz/faxmail/faxmail.htm * *==========================================================*
Response:
Questions: 1) What shuts the backup generator off again ? Is this a programmable time interval or other arrangement ? 2) What are you using for an alternative load ? Water heater perhaps ? Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste!
Waste is all relative in this context. As a windpower user, I dump a lot of power as heat, but it is not every day. If I built a h= eatpump, this would not be worth while unless it was in frequent, if not constant use. I would do better building another windmill = than a heatpump. Then I would have more power during periods of light winds. Or maybe some photovoltaics. But when there is loads= of wind, I just enjoy basking in the dump load heat, and soaking up nature’s abundance of power… 4. Since the FET bridges are so simple and cheap to produce, and since you have multiple units around the house you’re not going to be adversely affected by a failure in the way that you would if you were using a single inverter to run all your appliances. 5. The FET bridge can be designed to operate at quite high pulse-rates (5Khz+) which makes filtering the output wave very easy with the result that RFI is significantly reduced. I was thinking of going commercial with these things if there was enough interest.
Sounds a bit ambitious, but that’s not really a criticism. 240 volts Dc is said to be pretty lethatl though.. ******* FROM: Hugh Piggott********** Off the grid, on windpower since 1978 Small scale wind energy specialist. ****Scoraig, Highlands of Scotland****
Response:
In article <, The electricity gets diverted to heating water only when the battery bank is full. Wind turbines must always see a load otherwise they fly apart, so when the battery can no longer be the load the power must be diverted to an alternative load such as a water heater. Good grief what kind of wind generator are you using?
A Whisper 1000. A "good" wind generator will have a variable pitch propeller, the pitch of which can be either mechanically controlled by a centrifugal mechanism or (in the case of a more sophisticated unit) by a microprocessor and small servomechanisms.
I’m not aware of any small wind generator with those features. All the wind generators for individual AE systems I’ve seen use fixed blades with a mechanism to tilt the unit back in high wind. — John A. Stanley
Response:
4. Since the FET bridges are so simple and cheap to produce, and since you have multiple units around the house you’re not going to be adversely affected by a failure in the way that you would if you were using a single inverter to run all your appliances. 5. The FET bridge can be designed to operate at quite high pulse-rates (5Khz+) which makes filtering the output wave very easy with the result that RFI is significantly reduced. Sounds a bit ambitious, but that’s not really a criticism. 240 volts Dc
is said to be pretty lethatl though.. To get 230v(rms) from these units he’d need more than 240vdc input, assuming he is aiming for a sine wave output. I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches. At lower voltages I would consider dc to be safer than a corresponding ac voltage. The body responds particularly badly to frequencies in the 50-60Hz range. Funny that this has become the world standard. At the 300 or so volts that he will need, both are pretty lethal. Use fuses rather than circuit breakers. A bank of batteries wired in series can produce more current than a typical residential feed from the local electric company. This can weld a circuit breaker together with the circuit still closed, defeating the purpose of the breaker. The devices are being "marketed" here as FET-bridges. Each bridge will require a timing and control circuit. The outputs will beat against each other, producing voltages between two outlets which may be unexpected and may cause trouble with some older audio equipment, which connects signal and chassis ground to one side of the line. An earlier poster mentioned that the devices should have a safe failure mode. Whenever I have had a similar idea I have been reminded by the people I work with that "H-bridges go BOOM in the night". A central inverter, on the other hand, can provide transformer isolation between the dc and ac components. Failures should damage only the inverter, rather than suddenly applying dc to your various induction motors around the house. Any audible whine from the inverter can be locked in the garage, rather than being allowed to come from a box mounted behind each outlet. RF noise can be filtered at the inverter and never distributed through the house. (wishfull thinking) Be careful. Duncan. ( inverters keep the computers running… )
Response:
In article <, In article <, A "good" wind generator will have a variable pitch propeller, the pitch of which can be either mechanically controlled by a centrifugal mechanism or (in the case of a more sophisticated unit) by a microprocessor and small servomechanisms. I’m not aware of any small wind generator with those features. All the wind generators for individual AE systems I’ve seen use fixed blades with a mechanism to tilt the unit back in high wind. Actually the first thing that struck me when I initially looked at alternative energy solutions was how lacking the whole area was in the use of modern technology. Inverters, fixed-pitch blades, low primary voltages, no use of intelligent control systems (when microprocessors are under a dollar each in quantity). Perhaps it’s just that those in the industry are "back to basics" types or maybe it’s just that the market will buy whatever’s offered – I don’t know.
I’d venture that it’s just a simple case of economics and KISS. Why create a more elaborate and more expensive system when a simpler and less expensive one can accomplish the same task? Personally, I’m perfectly happy that there isn’t pitch control on my windmill; it’s one less thing to break. — John A. Stanley
Response:
Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste! Waste is all relative in this context. As a windpower user, I dump a lot of power as heat, but it is not every day. If I built a heatpump, this would not be worth while unless it was in frequent, if not constant use. I would do better building another windmill than a heatpump. Then I would have more power during periods of light winds. Or maybe some photovoltaics. But when there is loads of wind, I just enjoy basking in the dump load heat, and soaking up nature’s abundance of power…
But why consider "dumping" energy it when you can store it and use it later or at least offset your other energy demands by pre-heating your hot water supply. Sounds a bit ambitious, but that’s not really a criticism. 240 volts Dc is said to be pretty lethatl though..
50VDC can be lethal if you don’t treat it with respect. Here in New Zealand we have a mains voltage of 230VAC which is 320V peak-to-peak yet very few people are electrocuted each year. In fact I suspect that if you’re energy self-sufficient, you’re in more danger of dying in a house-fire caused by high-resistance terminations overheating at the high currents demanded at 12V/24VDC than you are from electrocution. A properly designed and installed system should *never* expose anyone to the DC voltages, even when maintenance is required. As regards the AC, well people all over the world are happy to live with the dangers of 110-240VAC as the cost of reticulating reasonable amounts of electrical energy at managable current levels. *==[FREE-FAX GATEWAY INTO THE AUCKLAND NZ TOLL-FREE AREA]==* * FREE listings in NZ’s largest WWW Business Directory * * http://www.actrix.gen.nz/biz/faxmail/faxmail.htm * *==========================================================*
Response:
To get 230v(rms) from these units he’d need more than 240vdc input, assuming he is aiming for a sine wave output.
No, you only need 180VDC to get 230V (RMS) AC through the FET bridge. "Gasp" .. I hear you say, "how can that be?" Simple.. the peak to peak voltage of 230VAC is around 325. It varies from a maximum positive amplitude of +162V to a maximum negative amplitude of -162V. The FET bridge works by effectively reversing the polarity of the batteries across the output for each half cycle so the voltage goes from +162V down to zero (then the battery is effectively reversed) and up to -162V. The result is a peak to peak voltage of 325VAC and since it’s a sine-wave, the RMS voltage is around 230V. For 110VAC (RMS), you only need a DC voltage of around 85VDC so seven 12V batteries in series will do the job. One could argue therefore that since the DC voltage is less than 70% of the peak AC voltage that this system is safer than a mains-only setup. (before I get flamed, please note that I don’t have a calculator handy so these figures are "rough" but certainly in the ballpark.) I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches.
You can perform "zero current" switching through the FET bridges anyway which totally eliminates the arc. At lower voltages I would consider dc to be safer than a corresponding ac voltage. The body responds particularly badly to frequencies in the 50-60Hz range. Funny that this has become the world standard. At the 300 or so volts that he will need, both are pretty lethal.
But as I’ve just pointed out, you only need about 160VDC, which is still a voltage level that demands a degree of respect, but is certainly safer than 300VDC. The devices are being "marketed" here as FET-bridges. Each bridge will require a timing and control circuit. The outputs will beat against each other, producing voltages between two outlets which may be unexpected and may cause trouble with some older audio equipment, which connects signal and chassis ground to one side of the line.
There is the potential for that but it can be solved in several ways: 1. drive all the outlets in each room from a single FET bridge so that they are all synchronised. That means that unless someone is silly enough to run an extension lead from an adjoining room just to power their tuner, CD or whatever while the rest of the gear is plugged into a different bridge then there should be no problems. 2. use a central clock circuit which ensures that all the FET bridges are synchronised. I believe that this would be unnecessary overkill and erode the benefits of multiple redundancy that the FET bridge concept offers. An earlier poster mentioned that the devices should have a safe failure mode. Whenever I have had a similar idea I have been reminded by the people I work with that "H-bridges go BOOM in the night".
Indeed they can although failure mode is more frequently upon the application or removal of load than when in a quiescent state. The most probably cause of failure is driving a highly inductive load that generates large voltage spikes — but the output filtering (between the bridge and the outlet) provides significant protection against such spikes. Open-circuit FET failure can be easilly detected and used to shut-down the drive circuitry (thus avoiding a DC or half-voltage output condition). A double-short is best handled by an over-current circuit (which can be as simple as a fuse since the FETs are already destroyed at that point). A central inverter, on the other hand, can provide transformer isolation between the dc and ac components. Failures should damage only the inverter, rather than suddenly applying dc to your various induction motors around the house. Any audible whine from the inverter can be locked in the garage, rather than being allowed to come from a box mounted behind each outlet. RF noise can be filtered at the inverter and never distributed through the house. (wishfull thinking)
As I pointed out, it’s very easy to detect DC or half-voltage conditions resulting from a failure in the bridge and automatically shut down all output (thus protecting valuable appliances). Regarding RFI, the FET bridge should produce even less RFI than an inverter for the following reasons: 1. They are physically small units (no transformers and a small component count using much lower-current semiconductors) which allows them to be mounted in cases that provide a high level of RF shielding. 2. Simple filtering of the 5Khz switching curents (and harmonics) can tends to reduce the RF radiated by the DC and AC wiring to very low levels. Be careful.
Ain’t that the truth 
BTW: are their any enterprising manufacturers out there who might be interested in turning a working prototype into a commercial item? *==[FREE-FAX GATEWAY INTO THE AUCKLAND NZ TOLL-FREE AREA]==* * FREE listings in NZ’s largest WWW Business Directory * * http://www.actrix.gen.nz/biz/faxmail/faxmail.htm * *==========================================================*
Response:
To get 230v(rms) from these units he’d need more than 240vdc input, assuming he is aiming for a sine wave output. No, you only need 180VDC to get 230V (RMS) AC through the FET bridge. "Gasp" .. I hear you say, "how can that be?" Simple.. the peak to peak voltage of 230VAC is around 325. It varies from a maximum positive amplitude of +162V to a maximum negative amplitude of -162V.
I can’t let this pass unremarked. A 230V ac supply has an rms voltage of 230 volts, from the line to the neutral. The peak rises t= o 325V positive, and falls to 325 V negative. to achieve a full sine wave youwould need to have access to 325 volts. Not peak to p= eak, but line to neutral. This voltage needs to be reversed every half cycle. The FET bridge works by effectively reversing the polarity of the batteries across the output for each half cycle so the voltage goes from +162V down to zero (then the battery is effectively reversed) and up to -162V. The result is a peak to peak voltage of 325VAC and since it’s a sine-wave, the RMS voltage is around 230V.
Sorry, but I just can’t accept this. surely there must be others out there who agree with me on this! For 110VAC (RMS), you only need a DC voltage of around 85VDC so seven 12V batteries in series will do the job. One could argue therefore that since the DC voltage is less than 70% of the peak AC voltage that this system is safer than a mains-only setup. (before I get flamed, please note that I don’t have a calculator handy so these figures are "rough" but certainly in the ballpark.)
I can’t help flaming a bit. your calculations are OK, but the theory is all wrong. Peak voltages are certainly not calculted peak-= to-peak. I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches. You can perform "zero current" switching through the FET bridges anyway which totally eliminates the arc.
There is no ‘zero current’ when you are switching off a DC supply. You just have to break in and stop the current. ******* FROM: Hugh Piggott********** Off the grid, on windpower since 1978 Small scale wind energy specialist. ****Scoraig, Highlands of Scotland****
Response:
To get 230v(rms) from these units he’d need more than 240vdc input, assuming he is aiming for a sine wave output. No, you only need 180VDC to get 230V (RMS) AC through the FET bridge. "Gasp" .. I hear you say, "how can that be?" Simple.. the peak to peak voltage of 230VAC is around 325. It varies from a maximum positive amplitude of +162V to a maximum negative amplitude of -162V.
I can’t let this pass unremarked. A 230V ac supply has an rms voltage of 230 volts, from the line to the neutral. The peak rises t= o 325V positive, and falls to 325 V negative. to achieve a full sine wave youwould need to have access to 325 volts. Not peak to p= eak, but line to neutral. This voltage needs to be reversed every half cycle. The FET bridge works by effectively reversing the polarity of the batteries across the output for each half cycle so the voltage goes from +162V down to zero (then the battery is effectively reversed) and up to -162V. The result is a peak to peak voltage of 325VAC and since it’s a sine-wave, the RMS voltage is around 230V.
Sorry, but I just can’t accept this. surely there must be others out there who agree with me on this! For 110VAC (RMS), you only need a DC voltage of around 85VDC so seven 12V batteries in series will do the job. One could argue therefore that since the DC voltage is less than 70% of the peak AC voltage that this system is safer than a mains-only setup. (before I get flamed, please note that I don’t have a calculator handy so these figures are "rough" but certainly in the ballpark.)
I can’t help flaming a bit. your calculations are OK, but the theory is all wrong. Peak voltages are certainly not calculted peak-= to-peak. I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches. You can perform "zero current" switching through the FET bridges anyway which totally eliminates the arc.
There is no ‘zero current’ when you are switching off a DC supply. You just have to break in and stop the current. ******* FROM: Hugh Piggott********** Off the grid, on windpower since 1978 Small scale wind energy specialist. ****Scoraig, Highlands of Scotland****
Response:
To get 230v(rms) from these units he’d need more than 240vdc input, assuming he is aiming for a sine wave output. No, you only need 180VDC to get 230V (RMS) AC through the FET bridge. "Gasp" .. I hear you say, "how can that be?" Simple.. the peak to peak voltage of 230VAC is around 325. It varies from a maximum positive amplitude of +162V to a maximum negative amplitude of -162V.
I can’t let this pass unremarked. A 230V ac supply has an rms voltage of 230 volts, from the line to the neutral. The peak rises t= o 325V positive, and falls to 325 V negative. to achieve a full sine wave youwould need to have access to 325 volts. Not peak to p= eak, but line to neutral. This voltage needs to be reversed every half cycle. The FET bridge works by effectively reversing the polarity of the batteries across the output for each half cycle so the voltage goes from +162V down to zero (then the battery is effectively reversed) and up to -162V. The result is a peak to peak voltage of 325VAC and since it’s a sine-wave, the RMS voltage is around 230V.
Sorry, but I just can’t accept this. surely there must be others out there who agree with me on this! For 110VAC (RMS), you only need a DC voltage of around 85VDC so seven 12V batteries in series will do the job. One could argue therefore that since the DC voltage is less than 70% of the peak AC voltage that this system is safer than a mains-only setup. (before I get flamed, please note that I don’t have a calculator handy so these figures are "rough" but certainly in the ballpark.)
I can’t help flaming a bit. your calculations are OK, but the theory is all wrong. Peak voltages are certainly not calculted peak-= to-peak. I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches. You can perform "zero current" switching through the FET bridges anyway which totally eliminates the arc.
There is no ‘zero current’ when you are switching off a DC supply. You just have to break in and stop the current. ******* FROM: Hugh Piggott********** Off the grid, on windpower since 1978 Small scale wind energy specialist. ****Scoraig, Highlands of Scotland****
Response:
Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste! Waste is all relative in this context. As a windpower user, I dump a lot of power as heat, but it is not every day. If I built a heatpump, this would not be worth while unless it was in frequent, if not constant use. I would do better building another windmill than a heatpump. Then I would have more power during periods of light winds. Or maybe some photovoltaics. But when there is loads of wind, I just enjoy basking in the dump load heat, and soaking up nature’s abundance of power… But why consider "dumping" energy it when you can store it and use it later or at least offset your other energy demands by pre-heating your hot water supply.
Obviously I do heat my water with it if necessary, or I heat a room if it is cold. a heat pump or a bigger storage system would be = better ideally, but it all comes down to economics. Beyond a certain point it is beter value to capture more energy from the free s= ource than to obsessively conserve every morsel of what you caught before. Sounds a bit ambitious, but that’s not really a criticism. 240 volts Dc is said to be pretty lethatl though.. 50VDC can be lethal if you don’t treat it with respect. Here in New Zealand we have a mains voltage of 230VAC which is 320V peak-to-peak yet very few people are electrocuted each year. In fact I suspect that if you’re energy self-sufficient, you’re in more danger of dying in a house-fire caused by high-resistance terminations overheating at the high currents demanded at 12V/24VDC than you are from electrocution.
It isn’t peak to peak, its line to neatral peak, whaich is quite different. DC is very heavy on the switch contacts. It is also harder to break a Dc arc than an Ac one, so the shock hazard is higher. You ca= n design around all of these, but they are problems to be faced. A 325 volt battery makes sense to me, but I would cntralise the inverter. ******* FROM: Hugh Piggott********** Off the grid, on windpower since 1978 Small scale wind energy specialist. ****Scoraig, Highlands of Scotland****
Response:
In article <, Gasp! Nobody using solar, wind or other low-output electrical generation should be using a water heater unless it’s a heat-pump. Heating water with valuable electricity is such a waste! Waste is all relative in this context. As a windpower user, I dump a lot of power as heat, but it is not every day. If I built a heatpump, this would not be worth while unless it was in frequent, if not constant use. I would do better building another windmill than a heatpump. Then I would have more power during periods of light winds. Or maybe some photovoltaics. But when there is loads of wind, I just enjoy basking in the dump load heat, and soaking up nature’s abundance of power… But why consider "dumping" energy it when you can store it and use it later
My experience with wind energy is that on average I get one third to one half of the maximum out of it, as it is not every day that there is a 25MPH wind blowing. Alternative energy systems will always see days where there is far more energy coming in than can be stored unless one goes to the expense of buying an obscenely expensive energy storage system. or at least offset your other energy demands by pre-heating your hot water supply.
And space heating isn’t one of the other energy demands? Heck, if it’s cold, windy, sunny, and the battery’s full I switch on a 1500 watt electric heater! — John A. Stanley
Response:
RF noise can be filtered at the inverter and never distributed through the house. (wishfull thinking)
Which inverter are you using? I run an AM radio powered by a wall-wart running on juice from a Trace SW 4024 and there’s no inverter RF that I can detect. For me, your wishfull thinking is solid reality. — John A. Stanley
Response:
I wouldn’t worry about switching — just avoid capacitors on the input to the small units, or the contact arc will wipe out the switches. You can perform "zero current" switching through the FET bridges anyway which totally eliminates the arc.
There is no ‘zero current’ when you are switching off a DC supply. You just have to break in and stop the current.
I believe that where I was thinking of a small inverter powered from a 325 volt DC source switched through a standard light switch — much like standard house wiring — Bruce was thinking of the output from the switch as a digital input to the control circuitry of that small inverter, instructing the bridge to shut down after the present half-cycle is complete or instructing it to start the load by coming out of the "off" state and initializing a new output cycle. Switched outlets for flourescent lighting, garbage disposals, etc… The second method requires an input to the inverter that is always hot, and may require one to pull new wires. Because it allows one to quit worrying about damage to the switch when it is called upon to charge a set of filter capacitors this method will allow one to address the problem of RF radiation from the DC input wires with standard filtration techniques. Yet another thought comes to mind with this scheme. Some people really like the output of incandescent / halogen light bulbs. The voltages available in his house would be 325vdc and 240vrms. It seems silly to run an incandescent load off an inverter, but the available DC is much too strong for the bulbs available readily. He could tap off his battery bank at 240vDC, but he will then risk overcharging the batteries excluded from that tap. He could change all his fixtures to take _three_ US-style 110 volt bulbs in series. He could live with the irony of wasting a bit of power at the inverter in order to feed a pretty sine wave to a load that won’t appreciate it. I’m glad to see people are thinking along the same lines I follow… and outside the context of work, too. Look, ma, I’m helping, I’m helping. Duncan.
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In article <, A "good" wind generator will have a variable pitch propeller, the pitch of which can be either mechanically controlled by a centrifugal mechanism or (in the case of a more sophisticated unit) by a microprocessor and small servomechanisms. I’m not aware of any small wind generator with those features. All the wind generators for individual AE systems I’ve seen use fixed blades with a mechanism to tilt the unit back in high wind.
Actually the first thing that struck me when I initially looked at alternative energy solutions was how lacking the whole area was in the use of modern technology. Inverters, fixed-pitch blades, low primary voltages, no use of intelligent control systems (when microprocessors are under a dollar each in quantity). Perhaps it’s just that those in the industry are "back to basics" types or maybe it’s just that the market will buy whatever’s offered – I don’t know. It strikes me that since it’s really quite difficult to reliably and economically extract reasonable amounts of power from the environment (ie: levels that don’t require you to alter your whole life-style to accomodate them), building systems which make optimal use of such resources is a pretty good idea. My ultimate (but as yet unrealisable) goal is to create an alternative energy solution which allows an "average" house to be disconnected from the grid and switched to environment-only energy without the need to buy new appliances, add a gas-fired hot-water cylinder, worry inceasantly about the dangers of accidentally leaving a light on overnight etc. We already have the technology to achieve much of this. Well designed wind and PV generation systems can provide reasonable levels of energy in a wide range of conditions. Energy storage is a bit of a problem at present with conventional choices such as lead-acid batteries only having a relatively low life and limited capacities while newer technologies such as ammonia dissociation/recombination and fuel cells show promise but have yet to become a viable option. Until we get *major* breakthroughs in energy generation and/or storage, the best solution is to work at improving efficiencies. Saving 15W per hour by using a 200V wind-generator instead of a 12V one is one example. PIR-controlled room-lighting can also trim a lot of watt/hours off of consumption as can variable-pitch wind-generators, heat-pumps and the like. My own calculations indicate that by taking advantage of these efficiencies I’ll be able to disconnect from the grid with the only concessions being the addition of solar water-heating pannels and a gas-oven instead of electrical (we already use the microwave more than most) and a standby generator "just in case". I’ve never examined the size of the alternative-energy market but it must be very small or I’m sure that someone would have already produced better solutions than those which most people seem to be using at present. *==[FREE-FAX GATEWAY INTO THE AUCKLAND NZ TOLL-FREE AREA]==* * FREE listings in NZ’s largest WWW Business Directory * * http://www.actrix.gen.nz/biz/faxmail/faxmail.htm * *==========================================================*
Response:
In article < Hugh Piggott < writes:
The FET bridge works by effectively reversing the polarity of the batteries across the output for each half cycle so the voltage goes from +162V down to zero (then the battery is effectively reversed) and up to -162V. The result is a peak to peak voltage of 325VAC and since it’s a sine-wave, the RMS voltage is around 230V. Sorry, but I just can’t accept this. surely there must be others out there who agree with me on this! you are dead on, hugh. 120 V service is 120Vrms line to neutral which is 170V peak to neutral and 340 V p-p. another handy number to have is that three 120V phases are 208V line to line.
Response:
In article < (Bruce Simpson) writes:
[ stuff deleted ] My ultimate (but as yet unrealisable) goal is to create an alternative energy solution which allows an "average" house to be disconnected from the grid and switched to environment-only energy without the need to buy new appliances, add a gas-fired hot-water cylinder, worry inceasantly about the dangers of accidentally leaving a light on overnight etc. We already have the technology to achieve much of this. Well designed wind and PV generation systems can provide reasonable levels of energy in a wide range of conditions. Energy storage is a bit of a problem at present with conventional choices such as lead-acid batteries only having a relatively low life and limited capacities while newer technologies such as ammonia dissociation/recombination and fuel cells show promise but have yet to become a viable option. Until we get *major* breakthroughs in energy generation and/or storage, the best solution is to work at improving efficiencies. Saving 15W per hour by using a 200V wind-generator instead of a 12V one is one example. PIR-controlled room-lighting can also trim a lot of watt/hours off of consumption as can variable-pitch wind-generators, heat-pumps and the like. [ more stuff deleted ] A year ago when I started reading about the current state of solar power technology, I was supprised by both how much more expensive it is to run a solor powered home, and also by how much more efficient some of the appliances in a solar powered home are in comparison to conventional appliances. However, things such as a sunfrost, compact florescent lights aren’t showing up in people’s homes, who done’t read this newsgroup or similar material. IMHO, there’s a lot that can be done now to change the infrastructure in the United States and probably other countries so that the total power requirements can be met by environmental friendly methods. Also, It’s inconceivable to me that in my lifetime people who live in high density, low wage housing will be using anything by grid electricity in my lifetime. For example, the "politically correct" company I was working for part time had an extra old laser printer, so they used it as an extra printer with paper which was already printed on one side. But when I pointed out just how much electricty it took to keep the printer on, they turned if off, and started trying to use duplex mode more often on the main laser printer. A lot of people still use incadescent lights because that just don’t realize how good compact florescent lights have become. I holiday gift of a compact florescent light to people like this, with the suggestion to place it in a fixture that they tend to keep on for long periods of time would help change the climate towards florescent home lighting. When I was out in-line skating at a middle school track the other day, I thought how perfect a school would be for a solar powered hot water system, since the hot water would be used after gym classes, and after-school sports, the times that would minimize the need for storage. A well written proposal to a school board might get a system installed for the school, and at least would get people who read the proposal to realize how short the pay-back period is on modern systems. They might install one for their own home. This said, I think it’s great some people are going completed self-sufficient witheat some people are going completed self-sufficient with their electrical needs despite the extra cost, and hope to do that same thing myself some day after I finish graduate school. Eric Riehl
Response:
: you are dead on, hugh. 120 V service is 120Vrms line to neutral which : is 170V peak to neutral and 340 V p-p. You’re 100% correct. Let me put it into slightly more verbose wording: A conventional 240V household service consists of two 120V lines that are 180-degrees out of phase, and a neutral. RMS line-to-line voltage is 240, and each line to neutral is 120. Peak-to-peak voltages are 170 and 340, respectively. : another handy number to have is that three 120V phases are 208V line : to line. But only if you have a delta wiring configuration. In a 3-phase ‘Y’ configuration, line to line voltage is 240, and line to common is 120. Harry C.