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Old 06-27-2010, 06:43 PM   #3486 (permalink)
Greg Fordyce
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Hi Darxus,

The controller and motor together form a Buck converter. In this image from the wikipedia article the motor is the load (on the right) and the inductor is the motor's field coils. The controller is the switch, diode and capacitor.

The buck converter circuit will drop the pack voltage down to a lower motor voltage automatically. This voltage will be mainly determined by motor rpm, as the motors rpm increases so does its back emf which will increase the voltage required to maintain the higher rpm.

I think what you are describing is a multiphase buck converter shown in the same article.

There are several advantages to this according to the article, less current ripple and splitting the load current. But notice the inductors, one for each phase, so we can't get away with using the field coils in the motor, we need to add external inductors, however it does look like you could mount the caps on the motor. Now it may be possible to get around this problem in some clever way, but looking at the rest of the circuit makes me think that if you are going to all this trouble you may as well design a AC controller.


Last edited by Greg Fordyce; 06-27-2010 at 06:44 PM.. Reason: spelling error
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