A: Generally, the leakage protection switch that protects the human body from direct or indirect contact with electricity has a protection current of 30mA. When the VFD works, leakage current will be generated. Because theVFD output is PWM (Pulse Modulation Width), there is a capacitance effect of a long cable between the motor cable and the ground. When using a shielded cable, the capacitance effect is more obvious. When the VFD is working, the capacitor is charging and discharging, and current flows into the ground through the capacitor, and then flows back to theVFD from the ground wire on the incoming side to form a current loop. Also due to the harmonic components generated by the VFD itself, the high-frequency harmonic currents that appear will cause the residual current protection device to malfunction and cause frequent tripping. Therefore, for the VFD use occasions, the front-end leakage switch is of little significance. Correctly grounding the inverter, motor and equipment is the best way.