Analysis and Comparison on Motor Core Losses with Si-IGBT and SiC-MOSFET Inverter Excitations

In recent years, the silicon carbide (SiC) power semiconductors haved been evaluated and proven to provide the superior overall performance for power-electronic converters and electric vehicles as compared to the silicon (Si) power semiconductors [1 – 4]. According to [2], the SiC-MOSFET switching device was assessed to offer the better efficiency and power density for a DC-AC inverter and DC-DC converter than the Si-IGBT switching device. Most of those studies focused on evaluation of losses in inverter and power-electronic converters. However, inverter and its power devices need to be also evaluated in the core loss of interior permanent magnet synchronous motor (IPMSM), because inverters are reported to have influence on the iron core loss characteristics [5], [6]. Authors in [5] showed that an inverter with low on-voltage power semiconductors has about 10-20% smaller iron loss than the one with high on-voltage power semiconductors. In our previous work [6], we carefully considered iron loss characteristics of electrical steel sheet with the Si-IGBT and SiC-MOSFET inverter excitations. The SiC-MOSFET inverter with low on-voltage has smaller iron loss than the Si-IGBT inverter with high on-voltage; this is a material evaluation of magnetic body. So as the next step, motor core loss should be carefully assesses by three-phase inverters using the Si-IGBT and SiC-MOSFET power devices. This paper investigates core loss characteristics of the IPMSM with the Si-IGBT and SiC-MOSFET inverter excitations. Models of two three-phase inverters are developed to excite the motor, where its parameters are referred from an experimental IPMSM in our laboratory. The first inverter uses the Si-IGBT devices, and the second inverter uses the SiC-MOSFET devices. The two inverters are controlled by PWM method with a low carrier frequency of 1 kHz and a fixed DC-link voltage; the motor is operated with a low rotational speed of 750 rpm and in load operational case. In computational analysis, motor core losses with the two inverters are compared and evaluated on both time and frequency domains; waveforms of stator phase voltage of the motor with the two inverters are also examined to demonstrate efficacy of the two inverters. In addition, the magnetic flux density and distribution contours of motor core losses are analyzed.