The frequency converter is a device that transforms the power frequency power supply (50Hz or 60Hz) into AC power of various frequencies to realize the variable speed operation of the motor. The control circuit completes the control of the main circuit, and the rectifier circuit converts the AC power into DC power. The circuit smoothes and filters the output of the rectifier circuit, and the inverter circuit inverts the direct current into alternating current. For inverters that require a lot of calculations, such as vector control inverters, sometimes a CPU for torque calculation and some corresponding circuits are needed. Frequency conversion speed regulation is to achieve the purpose of speed regulation by changing the frequency of the motor stator winding power supply.