I had an MX20 that was shorted out internally.

It read only ONE ohm, between each of the motor's three phase legs, when disconnected from the drive. (A good car read well into the megohms, when checked the same way)

When the car ran, (yes, it DID run like this), it set up a tremendous vibration, hammering the cab, machine, control, floor, you name it.

The V3F25 was crowbaring it's output on max current, but as soon as the current flow subsided, it would turn on again, lather, rinse, repeat, lather...you get it. Only this would happen many times a second. So the motor had torque, then none, then torque, then none, all at a high frequency, which set up a resonant vibration throughout the elevator and building. Sounded like a huge jack hammer.

Although the motor was shorted, the short was on the "other side" of some portion of the windings, which meant that there was still some active and usable windings, that would create magnetism when energized, albeit only for an instant before the drive crowbarred off, then on, then off, etc. This allowed the drive to turn the motor, even though the motor was nearly a direct short. Staccato torque! Also, the meter just reads ohms, but since it is an inductive winding with AC being applied, there is then impedance, so that helps limit current flow, of course.

Funny how that drive can limit the current flow, and prevent fuses from blowing.

I don't believe a V2F25 can turn a MX motor without the resolvers' angular position feedback. It needs to know what angle the motor is at. I think it works something like a big stepping motor, where the drive will only alternate phases when it sees the angular rotation of the motor. The drives' output is dependent on the angular info, or it quits playing ball.

And if you connect an MX motor to a standard VVVF drive, I think it might just dither. Just a guess, because I never had a chance to test that theory. We will know more about this, yes, we will..when I have time..hah hah..