| 摘要 |
<p>The annoying, audible hum which is usually encountered during low speed operation of a permanent split capacitor motor is substantially eliminated by a control circuit which is connected in series with one of the motor's windings. In the illustrated embodiment the circuit comprises an NPN transistor having its emitter-collector circuit connected in series with the motor capacitor, and auxiliary winding. The transistor collector terminal is connected, during motor operation, to one side of an AC power supply and through a fixed resistor to the transistor and through a potentiometer and a fixed resistance to the emitter. By adjusting the potentiometer to vary the resistance in the emitter-base circuit the current flow in the emitter-collector circuit can be controlled to vary the speed of the motor,</p> |
