How to wire a VFD to a motor? Three phase and single phase VFD wiring

What is the use of VFD and where is it used

A VFD is a device which can control the rotational speed of the AC motor, the rotation is controlled by adjusting or controlling the frequency and voltage supplied to an electric motor. VFD is also called as variable speed drives, adjustable frequency drive or AC drive. A VFD can control the speed torque and direction of an AC induction motor. The AC input will be of fixed voltage and fixed frequency so the VFD will change this input into a variable voltage and variable frequency. VFD is needed to match the speed and torque of the drive to process requirements. It can save energy and improve efficiency. So basically a VFD is a motor drive that can control the speed, torque, direction, and horsepower of a motor.

What are the benefits of using VFD

  • Energy saving
  • Low motor starting current
  • Thermal and mechanical stress in the motor is reduced
  • Simple installation
  • High power factor
  • Better system control
  • Higher efficiency
  • Remote mounting
  • Protection from high inrush currents

How to wire a VFD and what are factors that must be considered while doing it

Before starting the wiring, we must turn the power off, and in case of turning the power on proper equipment must be used for it. In order to wire a VFD to a motor, we must check certain factors before connecting it to the motor check the load amps of the motor and make sure the VFD that we use must be compatible with it. After that use the proper wire gauge suitable for the load amps. There is three-phase and single-phase VFD’s, in the single-phase VFD it has single phase input and three-phase output so we can control a three-phase motor by using a single-phase VFD.


At first, we must locate the input and output terminals of the VFD, in the VFD there will be two terminals for the input consider the input terminals as R1 and R2 of the VFD and three for the output section, the out terminals can be named as G1, G2, and G3. Connect the ground wire from the circuit breaker to the VFD’s input section and the ground wire would be green the input wires that power the VFD will be black and red, black is connected to the R1 and the red is connected to the R2. The connection is shown in the below image the two input wires and the ground wire is connected to the VFD. The section in which the red and black wire is connected is the input section.



Now the connection of the output section, a ground wire is connected to the output section so that the motor can be easily connected. The black wire is connected to the G1 and then the red wire is connected to the G2 after that a blue wire is connected to the G3. So this is the way that we can wire a single phase VFD to a three-phase motor. The output connection can be seen in the below image





In three-phase VFD, the wiring is almost similar to the single-phase. The difference is that there is a third wire from the panel of the input section of the VFD whereas in the single-phase it was only two-wires the R1 and R2. So in a three-phase VFD, there are three input terminals and three output terminals and that’s shown in the above image.

Now we can turn the power on and the keypad will be light up, after that we can do the programming.