They may be used in DC wind generators, but most of those don't use DC motors. A DC motor will put out DC that's mostly clean (maybe some brush noise) and doesn't need a capacitor. This would be close to using one of the Ametek tape drive motors, only much larger.
If you've already got this motor, hook a scope or voltmeter up to it and spin it over somehow. If you get DC output then you're all set. If you don't get anything then the motor probably doesn't have permanent magnets built into it. It used part of the DC fed to it to create a magnetic field. You'll need to add magnets to it before it will generate power, in much the same way as any other motor conversion. It will probably require some machining.
> Ok, so since my motor is three-phase DC.
There isn't any such thing. Only AC has phases. If you rewind it, you may want to make it 3-phase.
The main difference between an AC generator (AKA alternator) and a DC generator is that the DC one usually has brushes to keep the polarity of the voltage coming out going in the right direction. If you spin a coil in a magnetic field (or magnets inside a coil) the result will be AC. In a DC motor or generator the brushes connect to each coil in one direction and then 180 degrees later they're connecting in the opposite direction because the shaft has turned. It's sort of the original rectifier (or a mechanical rectifier). Brushes have disadvantages: they wear out, make sparks and electrical noise, and add friction to make the motor/generator harder to turn. Generating AC is better because it can be done without brushes, and you use rectifiers to convert to DC. If you mount the magnets on the rotor (because they don't need wires connecting to them) then you don't need brushes because the coils aren't moving.
You should probably let the motor decide what voltage you're going to use. That will depend on how fast you can turn it. Probably the best thing is to get it spinning and measure.
Alan
