"Engineer" wrote in message
...
(snip)
Two points of information:
1. Shaded pole motors are not synchronous motors, they are
induction machines that run below synchronous speed by an
amount related to the torque load. This difference is
called "slip" and it's the means by which current is induced
into the rotor so that it can be pulled round by rotating
the stator magnetic field. No slip = no torque, so it can't
happen!

A synchronous machine must run at synchronous speed. If it
"pulls out" due to too much torque load, it stalls. In this
case the rotor field is provided by a DC current source.
Some synchronous machines are "induction start" - they
accelerate as induction motors under no load, then "pull
in".

**Thanks for clarifying the differences.


2. A resistance in series with the motor stator field, in
this case the shaded pole field coil, will slow it down but
will reduce motor efficiency. A capacitance is more
efficient (no I2R loss) but the motor loss due to high slip
remains. This is never done in an industrial drive motor but
will work on a small fan where efficiency is not the prime
concern. I'll be the first to admit it's not elegant, but
you can do it.

**You sure can. Some of the results can be unpredictable, due to the
inductance of the motor and the capacitance, when they form a resonant
circuit. It does, indeed, work, however.


--
Trevor Wilson
www.rageaudio.com.au