zero speed switch

[buckrod]

Is there any way to use the voltage from a coasting down motor for a zero-speed detection switch instead of installing a mechanical one?

 

[dpc]

It won't be reliable because the voltage will usually drop to zero, or very close to zero long before the motor coasts to a stop.

Once an induction motor is de-energized, it loses it excitation source and the voltage decays rapidly within a few cycles. There might be a very small voltage due to magnetization of the iron, but I don't think you could count on it.

Not that I've ever tried it.