Evaluation of total loss for an inverter and motor by applying modulation strategies

This paper evaluates total loss of an induction motor and a permanent magnetic motor drive system applying two various modulation strategies on each motor, which are the PWM operation and the six-step operation. At first, the loss analysis is implemented based on the theoretical model of an inverter and an induction motor. As a result, when the leakage inductance is less than 25%, the PWM drive should be used instead of six-step operation in order to obtain the minimum loss. On the other hands, when the leakage inductance is more than 65%, the six-step operation is suitable for obtaining high efficiency. Additionally, an optimization point of the switching frequency is mentioned according to the leakage inductance. The validity of the loss analysis is confirmed by simulation and experimental results in which an induction motor of 1.5 kW was used. Similarly, the total loss of the permanent magnet motor drive system is calculated based on the same method. When the synchronous reactance of the motor is lower than 26%, the total loss of the PWM with a 5 kHz carrier is lower than the six-step modulation. On the other hands, when the synchronous reactance of the motor is more than 26%, the total loss of the six-step modulation is smaller than the PWM with a 5 kHz carrier.