Assessment of motor core loss, copper loss and magnetic flux density with PAM inverter under dissimilar excitation angles

Abstract

This study is the first research to present a detailed assessment of core loss, copper loss and magnetic flux density of the interior permanent magnet synchronous motor (IPMSM) with pulse-amplitude modulation (PAM) inverter under different excitation angles in both no-load and load conditions. The PAM method automatically controls the amplitude of changeable DC-link voltage, and the excitation angle for switches in the inverter is varied from 120° to 180° according to a 12-step switching pattern designed particularly for the PAM-based inverter of IPMSM. For reference purpose, the pulse-width modulation excitation with a very high voltage modulation index is performed. Various conditions with changes in speed and torque are examined. Experimental results show that harmonic components produced by the PAM inverter in the IPMSM current, voltage and magnetic flux density have large effects on the motor core and copper losses; physics-based explanations and insights are also presented. The PAM under 135° excitation angle has an excellent performance in reducing IPMSM core and copper losses since it can significantly decrease the harmonic components in motor current, voltage and magnetic flux density. Furthermore, simulations using the finite element method are conducted to validate the experimental results of IPMSM core loss with the PAM excitations.