Can this work well ?

My friend told me that a electric motor vice versa can become a generator set if you turn the roto with the RPM given by the electric motor . Dear members can I accept this funny theory ?

Best Regards

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Depends on the motor.

Reply to
Richard Henry

Yes it can work, sort of. Most DC motors and universal motors will generate when rotated. Synchronous AC motors will function as alternators when rotated. Induction AC motors are more tricky. Most AC motors are induction types. They will function as alternators when hooked to power.

If they are not mechanically driven, they are motors taking power from the line and rotate at a speed less than synchronous speed. If they are mechanically driven faster than synchronous speed they become alternators and deliver power to the line. So, they either take power or deliver power depending on the speed they are driven.

Induction motors will not generate power if not excited by an AC power source. They do not make good stand alone alternators.

Reply to
Bob Eld

Yes, It can work , DC PM motors are most effective in this manner.

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Reply to

It's not a funny theory at all. Just about any transducer that can turn electric power into mechanical power can do the reverse, although some work better than others, and nothing is going to be optimal as both a motor and a generator.

A brushed, permanent-magnet or shunt-wound DC motor is going to be the best "generator" when you turn it, followed closely by a brushless DC motor (but only the motor itself; the controller would have to be specially built to take the generated AC from the motor and turn it into DC).

A brushed, permanent-magnet DC motor is close to the perfect example of a two-way electromechanical transducer.

Series-wound ("universal"), induction, and variable-reluctance machines will all work, grudgingly.

About the only thing that I can think of that has a very poor chance of working is a hysteresis motor.

Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

As many have stated, it depends.

But, think about it.

If you put 1Hp of electricity into a motor, do you get 1Hp out ?? No.

If you put 1Hp of mechanical energy into the shaft of a motor will you get 1Hp electricity out ??


So, reason states that getting some electricity out and getting some mechanical out is true.

But is it useful ??


The real numbers are left to the student as an exercise.


Reply to

Sure. Google for pumped storage (hydro electric). They use the same unit as a turbine/generator when they want power and as a motor/pump at night when power is cheap to pump the water back uphill so there will be water tomorrow.

Check out hybrid cars. They only have one motor/generator. When you want to slow down, they turn the motor into a generator and push energy back into the battery.

I think desiel electric trains use the electric motors as generators to feed big resistor banks (no battery) when they are going down hills.

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Reply to
Hal Murray

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