Power factor control in a slip energy drive

The control of slip-energy by means of a current source inverter connected in the secondary circuit of a slip-ring induction motor can provide a means of controlling the direction of energy flow for sub and supersynchronous operation and a means of controlling the power factor in the rotor circuit. The effect of power factor control can be to reduce the net line current and improve the overall power factor and efficiency. The method employed to achieve this did not maintain the required phase angle when driving through synchronous speed thus only manual adjustment was used. Delayed commutation was observed at supersynchronous speed resulting in an unwanted reduction in rotor power factor and consequently reduced torque operation. Further additional commutation periods were observed resulting in higher operating voltages within the inverter