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

A technique that optimizes flux level to improve the efficiency of an induction motor is discussed. When harmonics and saturation effects are considered, the slip of minimum loss, or optimal slip, depends on both the speed and the load torque. The measurements of speed and torque are achieved without conventional torque and speed sensors, using motor terminal quantities. The control strategy is divided into two stages. First, the optimal slip is searched by trial and error, and the results are tabulated in microprocessor memory. Then the motor is operated at optimal efficiency by simply tracking the optimal slip given in the table. Experimental results show good performance in energy saving and dynamic responses