Reversing a motor-Dose it really work as a generator?

Generally yes, but it depends on the type of motor.

A small permanent magnet DC motor like you find in a toy, or the fan motor from a car certainly works as a generator.

Del

The classic demostration for this is the St. Louis motor, a horribly inefficent but easy to see, small motor/generator that most physics labs probably have lying about somewhere.

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Dose is really spelled, "does."

AC induction motors will not act as a generator. There are types of AC motors which will act as generators/alternators, such as the one in your automobile, or universal types with brushes. Almost all DC permanent magnet type motors will act as generators, but BLDC (brushless DC) motors will not (unless they are designed to do so), as they are electronically commutated.

Thank you for your comments.

Sorry for the correction, but even induction motor could act as generator. Run it in reverse will not be usefull, you will need to run it at a speed greater than the synchronous speed.

In this case the induction motor will act as a generator (if the motor is connected to the grid, if not you have to put condensator in // to supply the reactive power to the motor).

All three phase motors can operate as a generator. both synchronous and induction 3-phase motors are good to go. You do need a prime mover to drive them of course. Single phase ac motors are out.

profsteam; why would't a single motor work? perry

Actually, I should have been a little more technical, but the person asking the question doesn't know much about motors, so I didn't bother.

Induction motors certainly can be generators, and they don't have to run backwards. In applications where motors are used to drive inertial loads, when the power to the motor is removed, the induction motors do not act like much of a generator at all, since they immediately start slowing down -- they must be driven to an overspeed to produce any power worth having.

I'll be glad to get as technical as anyone desires, but please allow me to be practical as well.

All three phase motors and generators run equally well in either direction.

profsteam