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#61
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Wind/Solar Electrics ???
On Tue, 20 Dec 2005 10:29:12 -0800, "RST Engineering \(jw\)"
wrote: It seems as though we are trying to build a cathedral foundation to hold an outhouse. It isn't like I'm LIVING in the hangar, nor am I there working all day every day. Sure, lights when you are elbow deep inside an engine are nice, but hardly bleeding edge solar design. What? Ten fluorescent fixtures with 80 watts of bulbs each? A drop cord with another 20 watt fluorescent bulb? Perhaps a hand drill twice a day WHEN you are working in the hangar? It's not a matter of building a cathedral foundation, but rather trying to design the least expensive foundation. But I guess if you're going to light 35 hangars with ten fluorescent fixtures that are on for a few minutes each day, you won't need much. As to the compressor, drill press, grinder etc., a gas generator for the few times a month you need them is quite in order and certainly less expensive in both the short and long term than gearing up for 100% solar for the peaks. Very reasonable, and what I would suggest depending on how much the surge is. Of course, that means you'll have to have wiring so that those items will plug directly into the generator, rather than going through the inverter. And, if you design the system correctly, letting the gas generator run for an hour every time you fire up and letting the batteries take a full charge from an inexpensive battery charger can add to the output of the solar system. It is extremely inefficient to bring the batteries up to full charge using the gas generator. Batteries charge more slowly as they approach full charge. Better get a reliable generator, then. I've done a little digging and it seems that Great Plains has the best pricing on solar panels. Harbor Freight has a little better pricing, but I need something that I can reliably get month in and month out (I'm the guinea pig for about 50 hangars) and I can never rely on Harbor Freight to have what I need when I need it. My best guess after doing a little educated digging is that I can come up with a system I can live with for a little over 1 AMU. Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA) |
#62
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Wind/Solar Electrics ???
"philkryder" wrote in message oups.com... Steve - How many equal "steps" are necessary for the MSW inverter to be a sufficiently close approximation to a "rotary" sine wave? Careful. Even true 'rotary' generators don't always put out a true sine wave. Even the very, very large commercial generators used in power plants, don't put out a 'pure' sine wave. The number of stator slots and rotor geometry cause a small amount of harmonics. The exact connections of windings is often used to help improve the fundamental and minimize some of the higher harmonics (6th, 9th and 11th are some of the more troubling ones). After it passes through several transformers, getting to the substation, most of the harmonics have been filtered out by the characteristics of the transformers. So the question, as usual, boils down to 'how good, is good enough?' daestrom |
#63
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Wind/Solar Electrics ???
I've heard that a boat is a hole in the water lined with wood, into
which one pours money. ;-) Do airplane people have a similar saying? An Airplane is a large mobile fan into which the owner is obliged to throw handfuls of money (to watch it blow away). David Johnson |
#64
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Wind/Solar Electrics ???
Modified Semantic Wave is correct.
"George Ghio" wrote in message ... wmbjk wrote: I take that to mean that you won't be providing any examples of sine wave inverters with stepless waveforms. What a shocker. Wayne Take it to mean that you can't prove that true sine wave inverters don't exist. Modified Square Wave inverters = True Modified Sine Wave inverters = False |
#65
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Wind/Solar Electrics ???
We previously went through this crap with CD players.
The sampling frequency was chosen to be 44.1 kHz, well beyond the range of human hearing. No filtering would be needed. Except for one thing...when they played the CD back unfiltered, people would find their tweeters melting for some weird reason....44.1kHz! at huge powers! Out came the drawing board and complex analogue (and expensive) filters were designed until one day some smart engineer discovered they could double the freq. in a computer and put out 88.2 kHz sampling noise and use a less efficient and less expensive filter. Well, the audio hype that came out then was "2 times oversampling" followed by 4x, 8x, 16x & 32x "oversampling". Shister and ignorant marketing people explained this as "reading the CD 16 times repeatedly and eliminating the digital errors" "You can eliminate scratches with this" In reality the "oversampling" technique was the development of a digital filter that made the analogue filter into a simple capacitor to eliminate the sampling noise. Any square wave can be filtered enough to produce a pure sine wave. The trick is the cost. Huge core inductors and capacitors to handle and smooth out big quantities of power cost money to design and money to produce. Not to mention the sheer weight of the beasts. Multistep waveforms can be filtered much easier. This is analogous the "oversampling" technique used in CD players of years past. Digital filtering is much easier and cheaper than the equivalent analogue filtering. It's not like an inverter, these days, doesn't have a computer chip inside then anyway. How little distortion do you need anyway? Most of it can be accomplished inside the computer and then just amplified to useful power levels. At a cost, of course, and a marketing tool for more money...always. "daestrom" wrote in message ... "philkryder" wrote in message oups.com... Steve - How many equal "steps" are necessary for the MSW inverter to be a sufficiently close approximation to a "rotary" sine wave? Careful. Even true 'rotary' generators don't always put out a true sine wave. Even the very, very large commercial generators used in power plants, don't put out a 'pure' sine wave. The number of stator slots and rotor geometry cause a small amount of harmonics. The exact connections of windings is often used to help improve the fundamental and minimize some of the higher harmonics (6th, 9th and 11th are some of the more troubling ones). After it passes through several transformers, getting to the substation, most of the harmonics have been filtered out by the characteristics of the transformers. So the question, as usual, boils down to 'how good, is good enough?' daestrom |
#66
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Wind/Solar Electrics ???
Tell us why anyone would modify a sine wave.
SolarFlare wrote: Modified Semantic Wave is correct. "George Ghio" wrote in message ... wmbjk wrote: I take that to mean that you won't be providing any examples of sine wave inverters with stepless waveforms. What a shocker. Wayne Take it to mean that you can't prove that true sine wave inverters don't exist. Modified Square Wave inverters = True Modified Sine Wave inverters = False |
#67
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Wind/Solar Electrics ???
"....We have a touch lamp that will not change
state on MSW, but will on generator" Do you know if these new smaller Inverter style generators are a close enough approximation for things like the laser printer? Just how good are the "sine" like waves on them? I thought someone was going to put a 'scope on one... |
#68
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Wind/Solar Electrics ???
"....It depends how you count "steps"."
Indeed. I suppose something like "the number of distinct voltage changes per cycle" might be a good first approximation of something to call steps and to count. In your example I would count something like "3" or maybe "2" or "4" - I always have trouble with boundary conditions... In any case, it seems that the device you had was effective. And the only thing I could imagine as having fewer steps would be a similar device that didn't have the pause at zero... And yet it was effective - I wonder if it would have worked with the light dimmer mentioned above... |
#69
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Wind/Solar Electrics ???
Steve Spence wrote:
philkryder wrote: Steve - How many equal "steps" are necessary for the MSW inverter to be a sufficiently close approximation to a "rotary" sine wave? That depends on what you are driving. A laser printer requires closer representation than a computer. The manufacturer of a particular load could tell you that information. The old test of whether something was sine or some version of square was a lamp dimmer. On a square wave unit the light goes full bright. We have a touch lamp that will not change state on MSW, but will on generator. A lot of ac loads are quite happy on dc. Almost anything that rectifies the mains waveform will run fine on dc of V_mains x 1.414. NT |
#70
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Wind/Solar Electrics ???
philkryder wrote:
"....We have a touch lamp that will not change state on MSW, but will on generator" Do you know if these new smaller Inverter style generators are a close enough approximation for things like the laser printer? Just how good are the "sine" like waves on them? I thought someone was going to put a 'scope on one... What are those Phil? NT |
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