VFD and Motor Connection Diagram for Forward and Reverse Rotation

Hey, in this article, we are going to see the connection diagram of VFD and Motor for Forward and Reverse Rotation. We will use external switches to rotate the motor in forward and reverse directions when we want. Variable Frequency Drive or VFD is an electronic device that can control the speed and torque of AC induction motors by varying the frequency and voltage supplied to the motor. 

They are commonly used in industrial applications for better energy savings, precise control, and easy operation. When it comes to controlling the direction of rotation (forward and reverse) of a motor using a VFD, we can use external switches or any other input method to give commands to the VFD to change the direction of the rotation of the motor.

We know that the rotation of the three-phase motor can be changed by interchanging any two phases of the three-phase input power supply. So when we give command to the VFD using switches it will interchange the phases to change the direction of the motor. 

The microprocessor in the VFD processes the input command or control signals received from the external switches and adjusts the inverter output. The microprocessor ensures that the correct sequence and timing of the phase currents are applied to the motor to achieve the desired motor direction. 

VFD also provides a very smooth and controlled transition between forward and reverse directions. It gradually changes the frequency and voltage to avoid abrupt changes that could cause mechanical stress on the motor and connected machinery.

PNP Mode Operation

In the PNP Mode, the control system employs a positive negative positive (PNP) logic scheme for signal inputs. PNP devices use a positive common reference voltage. So here, a positive voltage signal is sent to the input terminal to activate the function.

Here we have used two control switches (selector switches) for forward and reverse rotation. These switches are connected to the VFD's input terminals configured for PNP logic.

Wiring Diagram

Here, you can see the VFD and Motor Connection for Forward and Reverse Rotation in the PNP Mode.

We need to connect the forward control switch to the PNP input terminal assigned for forward direction control on the VFD. So, here we connected to MI1 Terminal.

We need to connect the reverse control switch to the PNP input terminal assigned for reverse direction control on the VFD. So, here we connected to MI2 Terminal.

Here, we connected the common terminal of both switches to the 24V terminal of the VFD.

NPN Mode Operation

In the NPN Mode, the control system employs a negative positive negative (NPN) logic scheme for signal inputs. NPN devices use a negative common reference voltage. So here, a ground signal (0V) is sent to the input terminal to activate the function.

Here also, we have used two control switches (selector switches) for forward and reverse rotation. These switches are connected to the VFD's input terminals configured for NPN logic.

Wiring Diagram

Here, you can see the VFD and Motor Connection for Forward and Reverse Rotation in the NPN Mode.

Here also, we have connected the Forward switch to the MI1 terminal and the Reverse switch to the MI2 terminal. Just the difference is here we have connected the common terminal of both switches to the DCM terminal.

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