What is a vfd in electrical? Variable frequency drive (VFD) is a kind of power control equipment which uses frequency conversion technology and microelectronics technology to control AC motor by changing the speed of motor. The VFD is mainly composed of rectifier (AC to DC), filter, inverter (DC to AC), drive unit, detection unit, micro processing unit, etc. VFD motor is a combination of variable frequency drive and three-phase motor to be used with AC 50Hz/60Hz power supply system. The VFD motor can adjust the speed of motor under various load conditions, completely eliminate the mechanical and electrical shocks and prolong the service life of mechanical equipment. And the variable frequency drive motor also works to protect against overload, overvoltage, undervoltage, phase loss and overheating.