Star-Delta Starter PLC program and Wiring_ Part 3

Introduction

This tutorial will guide you through the wiring process of a star-delta starter for a motor, as demonstrated in the third part of the series by RealPars. The star-delta starter is essential for reducing the initial start current of a motor, allowing it to start smoothly and gain speed before switching to a delta connection for full operation.

Step 1: Understand the Star-Delta Concept

• The star-delta starter operates by initially connecting the motor in a star configuration.
• This connection reduces the voltage applied to the motor, consequently lowering the starting current.
• After a short duration, the connection switches to a delta configuration, allowing the motor to run at full voltage and speed.

Step 2: Gather Required Components

Before starting the wiring process, ensure you have the following components:

• Three contactors (one for star, one for delta, and one overload relay)
• A timer or PLC for controlling the timing of the switch
• Motor with star-delta capabilities
• Power supply and appropriate wiring materials

Step 3: Wiring the Star Connection

1. Connect the Motor Windings:

   • Connect the motor's terminals in a star configuration.
   • Ensure that the common point of the star connection is accessible.

2. Wiring the Contactors:

   • Connect the first contactor to the motor's star terminals.
   • Use the overload relay to protect the motor from excessive current.

3. Power Supply Connection:

   • Connect the power supply to the first contactor.
   • Ensure correct voltage ratings are maintained.

Step 4: Wiring the Delta Connection

1. Reconfigure the Motor Windings:

   • Connect the motor terminals to form a delta configuration.
   • Each terminal should connect to the appropriate power supply line.

2. Connect the Delta Contactor:

   • Wire the second contactor to the motor's delta terminals.

Step 5: Implement Control Logic

• Use a PLC or timer to automate the switching process:
  • Program the PLC to maintain the star connection for a few seconds after starting.
  • After the designated time, the PLC should switch to the delta contactor.

Sample PLC Logic

IF Start_Button THEN
    Activate Star_Contactor
    Wait for 5 seconds
    Deactivate Star_Contactor
    Activate Delta_Contactor
ENDIF

Step 6: Testing the System

• After completing the wiring, conduct a test to ensure everything functions correctly:
  • Start the motor and observe if it operates smoothly in star mode.
  • Confirm that it transitions to delta mode after the set time.

Conclusion

In this tutorial, you learned how to wire a star-delta starter, including the concepts behind star and delta connections, the components required, and the implementation of control logic. Following these steps will help ensure that your motor operates efficiently and safely. For further learning, consider exploring additional parts of the series or hands-on practice with PLC programming.