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I need to speed control a 2 pole, shaded pole motor that runs a fan. I have used a simple triac 'light dimmer' control but the harmonic content at low speed settings means there is much vibration in the motor. Any ideas? Is there a simple PWM controller I could use?

Airmaster Fan sells a control manufactured by KB Electronics. It is rated for use with motors.

I assume the difference between the light dimmer and the motor rated unit is added inductance to attenuate the inrush current. The units are cheap enouph to make it worth a try.

Many Thanks, I will try them and let you know how I get on.

what's the difference between a shaded pole motor and a brush type motor ?

[edit: found the answer online elswhere]:
http://www.all-science-fair-projects.com...nchronous_motor


[This message has been edited by arm (edited 10-27-2004).]

A Shaded Pole Motor is a Brushless type, Single Phase Squirrel Cage Induction Motor, with a Short Circuited "Secondary" (Rotor), and a Shading Pole in the "Primary" (Stator) for Starting.

A Brush type Motor has Brushes contacting a Commutator, which is mounted on a rotatable, wound Armature.
The Commutator segments feed to/from the Windings on the Armature assembly.

There are a few AC Induction Motors with Commutators & Brushes (Syncronous, Repulsion Start, etc.), but for the most part, Induction Motors are Brushless Animals, with the Stator (Primary) Windings Physically Isolated (not connected in a "Physical" way), from the Rotor (Secondary).

The Stator would kind of equate to the Field windings of a Commutator Motor, and the Rotor equates to the Armature of a Commutator Motor.

They work nothing like one another - one functions via Induction, the other Repulsion.

Scott35