Fuzzy logic based improvements in efficiency optimization of induction motor drives

Induction motors are, without any doubt, the most used in industry. Motor drive efficiency optimization is important for two reasons: economic saving, and reduction of environmental pollution. In this paper, advantages of using fuzzy logic in steady-state efficiency optimization for induction motor drives are described. Experimental results of a fuzzy logic based optimum flux search controller are presented. For transient states a new original idea is introduced: a fuzzy logic based controller actuating as a supervisor is proposed to work with reduced flux levels during transients to optimize efficiency also in dynamic mode. Two different rule tables are designed, for torque transitions and for reference speed changes. With this controller efficiency can be improved in transients, and also search controller convergence speed is increased. Experimental results with a 1.5 kW induction motor drive demonstrate the validity of the proposed methods.