Power factor enhancement of induction machines by means of solid-state excitation

A novel concept for power factor correction of induction machines is introduced that employs an auxiliary three-phase stator winding together with a pulse-width-modulated (PWM) inverter to supply excitation power to the machine. When the PWM inverter is modeled as an equivalent capacitor, it is shown that two values of capacitance will yield unity power factor at a given operating condition. The effect of machine parameters on the critical value of capacitance is examined. A control algorithm to ensure unity power factor at the terminals of the main stator windings is presented, and its satisfactory operation is verified by means of a detailed analog computer simulation. >