The incoming reactor is used to limit the current impact caused by sudden changes in grid voltage and operating overvoltage, smooth the spike pulse contained in the power supply voltage, or smooth the voltage defects generated when the bridge rectifier circuit commutation, effectively protect the frequency converter and improve the power factor, which can not only prevent interference from the power grid, but also reduce the pollution of the power grid by the harmonic current generated by the rectifier unit. The main function of the outlet reactor is to compensate for the influence of long-line (20-200m) distribution capacitance, and can suppress the output harmonic current, improve the output high-frequency impedance, effectively suppress DV/dt, reduce high-frequency leakage current, protect the inverter, reduce equipment noise and premature aging of equipment.