Multi-speed control of single-phase induction motors for blower applications

A simple electronic scheme is studied for multispeed operation of a permanent split capacitor single phase induction motor used to run fractional horsepower blowers and pumps. Computer simulations are used to predict efficiency, harmonic distortion, and pulsating torque when the motor is fed at 60 Hz, 40 Hz or 30 Hz by means of a four-triac bridge circuit. Results of simulations and laboratory tests are compared, and show close agreement. This scheme may be a cost effective alternative to tapped-winding or pole-changing motors.<
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