Variable Frequency Drive universal frequency converter is a power control device that controls the AC motor by changing the frequency of the working power supply of the motor, and converts the power frequency AC power with constant voltage and frequency into voltage or frequency by applying the principle of frequency conversion technology and microelectronic technology The working process of the variable AC power device is to first convert the power frequency AC power supply into a DC power supply through a rectifier, and then convert the DC power supply into an AC power supply with controllable frequency and voltage to supply the motor.