"Matt" wrote in message
om...
Hello all.

I was looking at the router speed control from Woodcraft

(http://shop.woodcraft.com/Woodcraft/...%5Fid=3957&gif
t=False&mscssid=013CC5175C03A4EE58C6E39C42114560
) and had a question. I know there has been somewhat of a
disagreement in the past as to whether these things will tear up your
router motor or not, but my question is more general. It is stated
that it will work on any "motor with replaceable brushes." Why? Why
not a brushless motor (i.e., a table saw)?

I realize this may be some simple electronics question or something,
but I'd appreciate any info you guys might have.

cmk8895

Single phase AC motors are considered fixed speed devices their speed is
determined by the number of poles in the motor. You will also hear them
refered to as induction motors, this is because the energy comes in the form
of induced magnetic fields, i.e. no direct electrical connection between the
stator and rotor.

Brush type motors on the other hand have their electrical supply applied
directly to the rotor and most commonly have permanent magnets, their speed
of rotation is dependent on the average voltage supplied to them. When
supplied from a device like a speed controller that voltage is being turned
on and off continuously, the ratio of the on to off time determines the
effective voltage being supplied to the motor and thus the motor speed.