From holsen5629@aol.com Fri Dec 26 06:10:29 2003
Subject:Re: Speed Control Pedal

<< The first time I tried a speed control, it was with a household dimmer
switch mounted on a small utility box on my mike stand.  The You-can't-do-that's
were just what has been mentioned: A dimmer switch won't work. The motors
weren't designed to operate that way.  They will burn out if you try to run them
too slow - why would I want to do that?  Well, the motors didn't know and
disobeyed for a couple of years until I sold that Leslie after reconnecting and
taping the power cables. >>

"You can't do this" comes from the fact that Leslie motors are shaded-pole,
induction types designed to run at constant speeds. As long as the applied
voltage is within the motor's operating range, it will track to the AC line
frequency. However, once the voltage is reduced to the point where the motor no
longer has enough torque to run at its rated speed, it will start to slip and
slow down. This semi-stalled condition is very inefficient, and much of the
applied energy is converted into useless heat.

You probably never smoked a Leslie motor because they're fairly rugged, and
don't have to work all that hard spinning the rotors. However, if simply
reducing the voltage was a satisfactory means to control the speed of shaded pole
motors, there would have been no need for double motor stacks in two-speed
Leslies, or exotic motor controller circuits in older single speed models.

Harvey Olsen

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