Re: dc motor as gen

[Lee Hart <leeahart@earthlink.net>]

prasad wrote:
> dc machines are optimized to work either as a generator or motor...
> because of the commutator and brush settings.

True for simple motors. DC motors with interpoles and compensating
windings have fixed brush settings for motor or generator operation.

> What about the efficiency of the BDC motor as a motor and generator?

A brushless DC motor has its brushes and commutator replaced by
electronics. So, the answer depends entirely on how the electronics were
designed. Some designs won't work at all as a generator (super cheap
ones for fans and consumer products). Others work, but poorly (for
example, ones with transistors for motor operation, but only diodes for
generating). And others work the same as motors or generators (they have
full transistor H-bridges and all the necessary control logic).
-- 
Lee A. Hart                Ring the bells that still can ring
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