Shaft speed for 1500 watt generator

I have a U.S. Motors Corp. "Electric Plant" generator. It's a 1500 watt unit @ 120vac. I'd like to belt it to my 3hp Fuller Johnson Model K stationary which is throttle governed at 475 rpm.

What I don't know is the generator shaft rpm I'm aiming for. The name plate is unreadable, although it has a place for "speed", "amps" and" volts". The speed does have " 00", but that doesn't help a lot.

Any help would be greatly appreciated. Thanks, Doug

Input speed is strictly dependant on the output frequency you desire and the number of electrical poles in the machine. If you want 60hz out, you're going to have to turn either 900, 1200, 1800, or 3600 rpm on the input shaft. If you can count the poles of the windings, it is quite simple, divide 3600 by the number of pairs of poles, and you have your input speed. Depending on what you intend to power with the machine, frequency may not be important, such as lighting loads.

Some generators of the self regulating variety also require the speed to be close to the design RPM so the voltage comes out at the correct value.

If the generator, actually the alternator, is relativly new, it will most likely require an input RPM of 1800 (4 Pole) or 3600 RPM (2 Pole) for 60 cycle output. Many of the older units ran at 900 or 1200 RPM. The basic rule is that the more poles, the slower the operating speed.