Fuzzy-logic-based controllers for efficiency optimization of inverter-fed induction motor drives

Improvement of induction motor efficiency is important not only from the considerations of energy savings and cooler system operation, but also from environmental pollution prevention potential. Fuzzy logic can make controlling complicated systems, such as induction motor/variable speed drive combinations, easier. This paper describes a fuzzy-logic-based energy optimizing controller to improve the efficiency of induction motor/drives operating at various load (torque) and speed conditions. The energy optimizer is complemented by a fuzzy-logic-based sensorless (without a tachometer) speed controller which controls motor shaft revolutions per minute to maintain constant motor speed during the efficiency optimization process. An experimental test system with the controllers has been implemented in the laboratory to determine efficiency gains achieved with selected commercial motors. Efficiency gains as high as 12% have been achieved, with motor shaft speed being controlled to within 0.5%. Published by Elsevier B.V.