Experimental verification of EMC filter used for PWM inverter with wide band-gap devices

Abstract

This paper discusses the volume of an electromagnetic compatibility (EMC) filter and a cooling system that are used for a pulse width modulation (PWM) inverter with wide band-gap devices. First, the volume of reactors that are used in EMC filters such as common mode choke coils and differential mode choke coils is theoretically estimated. Then, the relationship between the carrier frequency of the PWM inverter and the total volume of filter reactors is clarified via simulation. Moreover, the relationship between the carrier frequency and the volume of the cooling system is calculated on the basis of on experimental results. The total volume of the inverter system that contains the filter reactors and cooling systems is reduced by 54% at a carrier frequency of 300 kHz using a two-stage filter, as compared to the case of a carrier frequency of 150 kHz with a single-stage filter. In addition, an induction motor is driven by a prototype GaN-FET inverter system having a carrier frequency of 300-kHz. As a result, the conducted emission is suppressed below the limit prescribed by CISPR-11 Group 1. Therefore, the proposed design method for EMC filters is validated experimentally. Furthermore, the power loss of the EMC filter is less than 2% as compared with the total loss of the GaN-FET inverter system.