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

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