Motor Core Losses Evaluation with PWM and PAM Inverter Excitations in Computational Analysis and Experiments

The interior permanent magnet synchronous motor (IPMSM) and blushless DC (BLDC) motor can be controlled by either the pulse-width modulation (PWM) inverter excitation or pulse-amplitude modulation (PAM) inverter excitation [1–5]. The authors in [2] evaluated losses of the PMSM in high-speed drive of 50 krpm to 200 krpm, where the carrier frequency is from 25 kHz to 200 kHz. Motor drive system used in electric vehicles (EV) requires the variable voltage and variable frequency operation for motor velocity control. Although the PWM inverter can make variable voltage and frequency, its output waveform is usually complicated. The PAM inverter requires an additional DC-DC converter for variable voltage, but it has simple output waveform as the 120-degree commutation technique [3]. Besides, the low carrier frequency and rotational speed affects the total core loss of IPMSM considerably. Our study focuses on this issue with the PWM and PAM inverter excitations in both no-load and load operational cases of the motor; the evaluation is conducted with computational analysis and experiments. Moreover, response of the magnetic flux density in stator and distribution contours of motor core losses with the two inverters are analyzed in computational simulation.