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Old 09-07-2012, 01:46 PM   #1 (permalink)
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Motor amps vs battery amps

I was talking with Darin the other day about this and I think we got it figured out. But, if someone is sure or can explain it better it would be great.

Lets say you have a 100V battery pack. You apply that 100V to your motor and it spins up to 4000 rpm at some load. Now, you reduce the amperage with a pwm controler to the motor until the rpms are at 2000. Lets say you are now applying 100A to the motor. Since your only at 2000 rpm its only requiring ~50V (half of the 100V @ 4000 rpm) to achieve that rpm. The motor is using 50V * 100A = 5000W. But, your battery pack is 100V, not 50V, yet it is still putting out 5000W. So, your battery amps are 5000W / 100V = 50A. So the motor is seeing 100A but the battery pack is only seeing 50A.

Is this correct?

edit: added pwm controller info

Current project: A better alternator delete
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