It's incredibly unlikely that a small generator would put out square wave, or mod sine. It's so much easier for a small, inexpensive generator to spin a coil, and produce natural sine.
a buddy put several generators on a techtronics scope, none were nice sine waves like the power company provides
"Stormin Mormon" wrote in news:h1ts7p$fjr$ snipped-for-privacy@news.eternal-september.org:
somehow someone was talking about inverters,which can either output square wave,modified or quasi-sq.wave,or sine wave AC.
Why it came up about generators,I don't know. An AC generator is always going to output a sine wave.
I'd think so, at least the spinning coil ones. Honda has some that have "inverter technology". Maybe the guy with the oscilloscope is picking up some harmonics, and other noise.
"Stormin Mormon" wrote in news:h20lg5$4j5$ snipped-for-privacy@news.eternal-september.org:
it's very possible it makes a lot of electrical noise.
You guys lost me. A Coleman is not a Honda inverter generator. Besides that, Honda claims their sine wave is better than what you get from your local utility.
"Ulysses" wrote in news:h22p8d$ben$ snipped-for-privacy@news.eternal-september.org:
Well,the OP mentioned "inverters" and MY post questioned why an inverter was used when the generator already makes a sine wave output. Then someone else mentioned Honda,and I researched that to answer my own question.
generating a sine wave from a DC supply requires switching large currents.the switchuing generates harmonics.
Now,the sine wave output may be very clean and right on freq,but the inverter's switching circuitry may radiate those harmonics,that could be picked up by other instruments. It takes very careful design to minimize radiated noise.
I have a similar problem with my 1850 but the output voltage drops at about 1100 watts load. The diodes appear ok, but I have no way to test the varistors in parallel with them. The problem started with a snapped governor lever which would have caused very high engine speed. That would have created a very high output voltage which I suspect could have damaged the diodes and/or varistors causing them to fail as the load increases. I hope to replace both and see what happens. Any thoughts?
I've put together a small page showing the repairs.
You have simply got to be an engineer. No one else puts that much detail and work into repairing something.
Probably a good thing you didn't visit my home page... :)
Storm> You have simply got to be an engineer. No one else puts that
Well, I never understood why, but, in automobile terms, I thought alternators had higher output at low speeds than generators did, but lower output at high speeds. Or that the voltage woudln't increase that much. A) Does your Powermate use an alternator? B) Am I right about what I thought. C) Would that make you wrong?
Did the load increase? Or did the load stay the same and output voltage increase? But I guess the second would make the voltage across both the dioades and the varistors increase, which is what you had in mind. Still, would that be enough to make them fail? I guess if they were not much better than the expected output one or both would.
The generator operates at a constant speed of 3600RPM in order to produce a 60Hz output.
Under no load the output is about 120VAC. It remains relatively constant up to about 1100 watts load. After that as the load increases it drops considerably, down to about 90VAC with a 1300 watt load. It should be capable of 1500 watts output continuously at 120VAC.
The governor in the engine failed and would have caused it to rev very high at full throttle. During this time the output voltage would have gone very high, and possibly caused damage to the diodes and/or the varistors. These components are on the rotor, and somehow connect with the field coils. I'm still trying to understand better how a brushless output generator somewhat self regulates its output voltage.
I've repaired the governor problem, and the engine works well now. However the next step is to ensure all components on the generator side are good in order to produce the proper power output.
I also have an 1850 coleman that i lost total A C output. I thaought it just had to be the capacitor . i replaced it... Nothing.same thing ...no voltage. Im about to give up on it.
Flash the field windings , it's lost the residual magnetism that it needs to start the generation process . I had the same problem with a Briggs unit a few years back .
sounds like MABRR it was shut down under full load? That sometimes collapses the kagnetic feild causing the generator to faik to energize. Flashing often fixes this. Shutting off loads before shutting down the generator odten prevents the problem
I think that's what happened to mine . I learned there is a way to get it going by plugging a drill motor into one of the outlets then spinning that drill with another (while holding the trigger down) while the generator is running . I already had mine partly disassembled so I did it with a 12V battery . Been working fine ever since .
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