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Posted by Tim Jackson on May 30, 2009, 5:26 am
Please log in for more thread options Scott wrote:
> On Fri, 29 May 2009 08:06:06 -0700, in alt.energy.homepower, "Ulysses"
>
>> Hi guys. I attached the coils and rotor (the entire PMA) from a Honda
>> eu2000 generator to a 4 HP engine--direct drive, just like it originally was
>
> Isn't the EU2000 an inverter type generator? I've read that many of those
> generate relatively high voltage internally, using the inverter to convert
> it to the 120v AC power you want. Supposed to be more efficient that way.
> IIRC the manual for my RV's 3400W generator says that it feeds 400 volts to
> the inverter, so I wouldn't be surprised if you saw an open circuit voltage
> of 600 or more.
>
I don't know about he design of this generator, but a couple of things
spring to mind. One is that the OP said he used a 200V capacitor and
got 600V output. That would start things smoking pretty quickly once
the capacitor collapsed. The other is that small alternators generally
operate at several hundred Hz: generating 50/60Hz directly is
inefficient at small scales (even a 4-pole machine would be turning at
only 750/900rpm). Were the diodes used appropriate for this service?
If you use regular power diodes at this sort of frequency, they will get
pretty hot too, the long turn-off time means they are an effective short
circuit for a while during commutation. It is important to use
high-speed diodes.
Tim Jackson
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