Abstract: SQ flat wire common mode choke are commonly used in black household appliances such as TVs. This type of inductor has the advantages of high production automation, good consistency, and high-frequency interference suppression, but it has not been used in inverter refrigerator products. While in inverter refrigerators using SQ flat wire common mode choke with the same size and inductance as the commonly used toroidal common mode choke, the inductance fails, resulting in abnormally high disturbance voltage in the low frequency band. Studies the failure cause of SQ flat wire common mode choke being inductor core saturation. Core saturation is due to SQ common-mode choke owning the smaller core cross-sectional area and larger leakage inductance compared to toroidal common mode choke, and compared to TVs and other black household appliances, inverter refrigerators have larger peak operating currents and larger inverter carrier leakage. Therefore, the SQ flat wire common mode choke is prone to saturation and failure under the combined action of common mode current and differential mode current. The method of increasing the magnetic core area and reducing the number of winding turns is proposed to reduce the magnetic density in magnetic core, can avoid the saturation failure of the magnetic core, so that the SQ flat wire common mode choke can be used in inverter refrigerator products.

Key words: EMC, CM Choke, Core Saturation, CM Current, DM Current