Elimination of instantaneous backward mmf in single phase induction motors

In the single phase induction motors, backward mmf causes torque and speed pulsations. This paper presents a new method to eliminate the instantaneous backward mmf to improve the performance of the single phase induction motor. In the proposed method a calculated reference current which is in quadrature with main winding current instantaneously, is injected to the auxiliary winding. The “Hilbert transformation” is used for obtaining the reference current of auxiliary winding by using the current of main winding. The proposed control scheme is simple and it does not need any position or speed encoder sensors. Basic system operation and theoretical analysis are discussed and simulation results in comparison with conventional method which uses sinusoidal voltage supply are presented to validate performance of the proposed method.