A novel technique for optimal efficiency control of current source inverter fed induction motor

This paper deals with the realization technique that optimizes the flux level to improve the efficiency of an induction motor. When harmonics and saturation effects are considered, the slip of minimum loss, or optimal slip, depends both on the speed and on the load torque. The measurements of speed and torque are achieved with motor terminal quantities dispensing with conventional torque and speed sensors. The control strategy is divided into two stages. Firstly, the optimal slip is searched by trial and error and the results are tabulated in microprocessor memory. Then the motor is made to be operated at optimal efficiency condition by simply tracking the optimal slip given in the table. Experimental results show good performance in energy saving and dynamic responses.