Simple motor operation using PLC

  PLC  Ladder motor  Problem:

Controlling the running state of the 1 ph motor by PLC ; pressing START and STOP pushbuttons i.e. motor should remain in ON state after START pushbutton is pressed and should OFF when STOP pushbutton is pressed. Checking if the Motor is running normally by pressing TEST pushbutton.

  Number of PLC Inputs Required

X0 – START pushbutton to Start Motor

X1 – STOP pushbutton to Stop Motor

X2 – Error signal from Motor to PLC.

  Number of PLC Outputs Required

Y0 –1 phase Motor

PLC Ladder Programming: 

PLC Ladder Program Description: 


  1. Press START button lightly and X0 = ON. The Motor will keep running if no error occurred (X3 = OFF). The action can be practiced by a latching circuit which takes output Y0 as one of the input condition to keep the motor running even if the START button is not pressed(See normally open contact Y0 below X0).
  2. When STOP button is pressed, X1 = ON and Y0 = OFF. The motor will stop running.
  3. If error occur (X3 = ON), Y1 will be OFF and the motor will stop running.
  4. When TEST is pressed (X2 = ON), Y0 = ON. The motor will start running if no error occurred (X3 = OFF). On the contrary, when TEST is released, the motor will stop running. The testing function is performed by this process.

Also read

Introduction to SCADA

PLC Interview Questions with Answers Part 2

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