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Old 09-07-2012, 02:49 PM   #7 (permalink)
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A pwm might use a stabilizing capacitor on the input, and output and there would be two ways of measuring the current and voltage. The results would depend on how exactly the pwm is built. Ill give multiple examples and their results for simplicity I will ignore voltage losses through the system.

With no capacitors on either side.
The average and instatanious (single pulse) current would be the same, during the on phase the voltage would be the same as the battery voltage, and drop to zero during the off phase. The average voltage on the motor (multiple pulses) which is what a typical DVM would see would be the battery voltage times the duty cycle. ex. 100v * 50% duty cycle would be 50v. I'm not entirely sure about the voltage part because of the back EMF from the motor.

Capacitor on the input, not on the output.
The average and instatanious current on the battery pack should be about the same. There will always be some ripple. The current and voltage on the ouput would be the same as above.

Capacitors on both the input and output.
The current on both sides will be pretty steady, and approxametly the same. The voltage on the motor side will be lower than the battery side, and this is not a sign of a problem.
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