Abstract: Surge is the main item in the electromagnetic compatibility test of refrigerator, and it is easy to fail the test, one of the important reasons is that the insulation of the compressor motor is insufficient and the inverter circuit board is damaged. If the compressor motor insulation is broken down, there will be a large surge current through the inverter circuit components and the components will be damaged. In this paper, it is analyzed that the surge test level is 4 kV, and the resonant amplification of the common mode inductance and Y capacitance of EMI filter circuit and the distributed capacitance of compressor let the voltage between the winding and the casing of the compressor reaches above 5.5 kV. The electrical gap between the winding of the motor in the compressor and the seat spring (connected with the iron core and the casing) is small, and the gap is easy to break down. After the breakdown, a large surge current will break the IGBT of the inverter circuit, burn the inverter board, and the surge test of the refrigerator cannot pass.

Key words: EMC, EMS, Surge, Distributed capacitance, Resonance oscillation