input wattage 4 motor to output wattage generator

[deadlymuskox]

Can you convert the wattage of an electric motor into what the output is for the same motor used as a generator?

 

[dpc]

Approximately.

 

[deadlymuskox]

so the wattage of a motor is the same as the output if you used it as a generator? would it be the same for volts and amps?

 

[davidbeach]

Assuming an induction motor/generator:

Output voltage will be whatever voltage the generator is connected to.

Output amps should not be allowed to exceed rated FLA.

Output watts should not be allowed to exceed rated HP (converted to kW).

Actual values (more or less than rated) depend on the circumstances of use.

 

[roydm]

If it's a squirel cage motor you won't get anything out of it becayse there is no field in the rotor. A DC motor should be about the same.
What type of motor are you refering to?
Roy

 

[davidbeach]

roydm, not true. A squirrel cage induction motor, driven at supersynchronous speed (negative slip) and connected to a power system that can supply VArs, will produce Watts. And, or course, there is a field on the rotor just as there is when it is operating as a motor, that's why the source of VArs is critical. Lacking a source of VArs, it won't work as a motor either.

 

[roydm]

Davidbeach,
I stand corrected, I was not thinking that it would be connected. Would it still generate if removed from the power system while running?
Roy

 

[itsmoked]

Long answer: It depends.
Short answer: No.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Hi Keith;
I set this up in a lab once. I electrically connected an induction motor in parallel with a resistor bank.
I mechanically connected a DC motor to the induction motor.
I energized the induction motor and the resistor bank.
I then ran the DC motor to push the induction motor above synchronous speed.
I then cut the power to the induction motor but left the resistor bank connected to the induction motor. The motor continued to supply current to the resistor bank.
At a later time, in a different lab with different equipment I was unable to maintain generation.
I agree with you; It depends and no. (With a strong maybe on the side.)
I understand that the addition of capacitors to the circuit improves the success rate dramatically.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Bill; I'm thinking the first shot may have had some mystery capacitance that was just enough. Perhaps the motor's winding layout?? Perhaps the load was slightly too much in your second attempt?

Interesting at any rate.

We had a fabulous power lab at my school but for some reason I never messed with stuff in there. A shame in hind sight.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

I remember as an apprentice connecting a PF correction capacitor across a large floor grinder and noticed that it's lights got brighter when I turned it off. I had the cap connected in the wrong place of course.
I always just assumed the field would collapse as soon as the windings no longer drew current.
Roy

 

[waross]

Back to the original question.
Motor ratings and generator ratings are based on the same parameters. The maximum current that may be carried by the windings without overheating, and the rated voltage. The maximum allowable voltage set by saturation issues.
The current in the motor windings is a combination of real current and magnetizing current. The magnetizing current is present whether the motor is producing torque or regenerating. This must be factored out before determining the maximum useful current of the motor as a generator.
If you follow davidbeach's suggestion to use kW or Watts the magnetizing current will be factored out.

Bill
--------------------
"Why not the best?"
Jimmy Carter