How Does a PLC Control a VFD and AC Motor? Complete Wiring Diagram

Electrical
1

Basic Industrial Automation Concept of PLC & VFD Motor Control

In this system, the PLC controls the motor through a VFD (Inverter), providing Start/Stop and Forward/Reverse operation.

Inside the PLC program

  • Latching logic keeps the motor running after pressing the Start button.

  • A status signal activates the Run indicator lamp.

  • The speed reference is scaled and transmitted to the VFD.

  • Forward and Reverse commands are managed safely through PLC logic.

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Process Flow

  1. PLC reads push-button inputs.

  2. PLC processes the control logic.

  3. Commands are sent to the VFD.

  4. The VFD controls motor speed and direction.

In summary

The PLC acts as the controller, while the VFD regulates the motor speed and rotation direction, ensuring efficient and reliable motor operation.