Speed control of single phase induction motor by using triac

Abstract

A single phase induction motor physically looks similar to that of a three phase induction motor except that its stator is provided with a single phase winding. The rotor of any single phase induction motor is interchangeable with that of a polyphase induction motor. A single phase winding would produce no rotating magnetic field and no starting torque. In the stator of a single phase motor is provided with an extra winding known as starting winding. Single phase induction motors are small motors having a wide field of usefulness where a poly phase supply is not available. They are generally used in fans, blowers, washing machines, refrigerators, etc. The speed of the induction motor can be varied in a narrow range by varying the voltage applied to the stator winding. This method of speed control is suitable for such applications, where the load varies approximately as the square of speed, such as centrifugal pump drives, fan load.