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

This paper discusses a volume of an EMC filter and a cooling system that are used for a PWM inverter with wide band-gap devices. At first, the volume of reactor that is used for EMC filter such as common mode coke coils and differential mode choke coils are estimated by theoretically. Then, the relationship between the carrier frequency of the PWM inverter and the total volume of filter reactors are clarified by simulation. Moreover, the relationship between the carrier frequency and the volume of a cooling system is calculated based on experimental results. As a result, the total volume of the inverter system that contains filter reactors and cooling system will be reduced by 54% at the carrier frequency of 300 kHz by using a two stage filter compared to case of the carrier frequency of 150 kHz by using one stage filter. In addition, an induction motor is driven by a prototype of GaN-FET inverter system with a 300-kHz carrier frequency. As a result, the conduction noise is suppressed below the limit of CISPR. Therefore, the proposed design method for EMC filters is valid in the experiment. Furthermore, the power loss of EMC filter is less than 2% compared with the total loss of the GaN-FET inverter system.