Evaluation of increasing rates in eddy-current loss of the motor due to carrier frequency

This paper describes that a theoretical formula for evaluating loss ratio in eddy current of a permanent magnet (PM) motor fed by a PWM inverter is proposed. A formula for evaluating the increasing rates of eddy-current loss in iron core due to carrier frequency corresponding to inverter output parameters (i.e., DC-bus-voltage, modulation index and modulation methods) are derived. Calculated and measured increasing rates of eddy-current loss in iron core were compared. According to the results of this comparison, the difference between the calculated and measured results is within 10 % when the modulation index is less than 0.7. The increasing tendencies of the calculated and measured increasing rates of eddy current loss agree well. The proposed theoretical formula can be applied for improving the efficiency of motor-inverter drive systems.