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From: nagle@netcom.com (John Nagle)
Subject: Re: How does a brushless DC motor work? WAS: Looking for brushless DC ...
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References: <3etatq$ngp@utdallas.edu> <Jan11.171234.67910@acs.ucalgary.ca>
Date: Sat, 14 Jan 1995 19:40:31 GMT
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morrow@cns8.cns.ucalgary.ca (Bill Morrow) writes:
>How does a brushless DC motor work, anyways? Don't you need some kind
>of varying field (e.g. a commutator, or AC voltage) to start the rotor
>spinning? I know little about 20th century motor design :).

       The "brushless DC motor" term is a misnomer.  They're really
synchronous AC motors, driven with power supplies that convert DC to AC at
the frequency and phase needed to drive the motor.

       Actually, all motors are AC motors, by the time power gets to the
windings.  "DC" motors have a mechanical commutator to convert DC to
AC in sync with the motor rotation.  "Brushless DC" motors dispense
with the mechanical commutator and its contact brushes, using
semiconductor power supplies and sensors to do the commutation.
This offers the potential of much better control.

					John Nagle
