Application of the Impedance Balance Method to Electric Compressor System with an Integrated Mechanical and Electrical Structure

The impedance balance method is used as a countermeasure against electromagnetic noise in power electronic circuits. In a previous research, the authors’ research group confirmed the reduction of common-mode voltage in a three-phase inverter circuit using the impedance balance method. However, it has been difficult to reduce common-mode voltage using conventional methods in an electric compressor system with an integrated mechanical and electrical structure, where the three-phase inverter and motor are housed in a single housing. This research describes a method to reduce the common-mode voltage in an electric compressor system with an integrated mechanical and electrical structure, using an impedance balance method. The first is to reduce the impedance of the balancing elements added to the circuit, and the second is to increase the impedance of the three three-phase output line connecting the three-phase inverter and the motor. By combining these two methods, the frequency bandwidth of the reduction effect was expanded from 2 MHz to 30 MHz, and a reduction in common-mode voltage of up to 30 dB was confirmed.