wrote in message
oups.com...

Dc motors wont work on ac of any frequency.

Not necessarily true. Clearly they work on ZF,

yes

and would continue to work
until the motor impedance became significant.

no. A dc motor is by definition one that runs on dc only. Typically
these are permanent magnet motors, in which direction of rotation
depends on polarity. Motor impedance is not the issue. Motor impedance
is the issue with universal or ac/dc motors.

Nope. I doubt anyone has EVER built a traction motor with permanent magnets.