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Old 07-26-11, 06:02 PM   #9
AC_Hacker
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Quote:
Originally Posted by Xringer View Post
I just used a flash light and mirror to check out the blower motor on the old wood stove (that's been sitting unused in the fireplace for many years). And, it looks like induction type, but no capacitor. I've used a lamp dimmer to control it (works fine).
If that motor is actually an induction motor, it relies on the alternating current to make it go. If it is an induction motor, using a light dimmer or a router speed controller will not change the speed, just reduce the torque.

There is an induction motor type called 'shaded pole' that does not use a cap to start, but it is still an induction motor and will need a variable frequency drive for speed control.

This from wikipedia:
Quote:
Speed control

The theoretical unloaded speed (with no slip) of the induction motor is controlled by the number of pole pairs and the frequency of the supply voltage. Synchronous motors should be run so that the shaft rotation speed is above the peak torque; then the motor will tend to run at constant speed. Below this, the speed tends to be unstable and the motor may stall or run at reduced shaft speed. Before the development of semiconductor power electronics, it was difficult to vary the frequency, and induction motors were mainly used in fixed speed applications. Many older DC motors have been replaced with induction motors and accompanying inverters in industrial applications.
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