How to Program the Star-Delta Control of PLC? (Complete Step-by-Step Guide)

In modern industrial automation, star-delta control is one of the most essential motor starting methods. It reduces the inrush current during motor startup and protects the system from mechanical stress. Today, we’ll guide you through how to program the star-delta control of a PLC – step by step. Whether you’re using Siemens, Mitsubishi, Delta, Omron, or Allen-Bradley PLC software, this guide will help you build, simulate, and test your program efficiently.

What Is Star-Delta Control in PLC Programming?

The star-delta starter is used to start a three-phase induction motor smoothly by initially connecting the motor windings in a star configuration, then switching to a delta configuration after a preset time.

When implemented using a PLC (Programmable Logic Controller), the process becomes automated, flexible, and safer. The PLC handles all timing, switching, and interlocking logic, reducing the need for manual control or hardwiring.

With PLC-based control, you can:

• Set precise start and delay times.
  
• Monitor motor current and fault conditions.
  
• Integrate with HMI software for visualization.
  
• Save and modify logic easily using programming software.

At PLCUnlock.com, you can download unlocked PLC and HMI software from top brands like Siemens, Mitsubishi, Delta, Omron, and Allen-Bradley to practice or deploy real-world star-delta control projects.

Basic Working Principle of Star-Delta Starter

Let’s break down the sequence of operations:

1. Start Push Button (START): When pressed, the PLC energizes the main contactor and the star contactor.
   
2. Motor Starts in Star Connection: The motor runs at 58% of line voltage, drawing less current.
   
3. Timer Starts Counting: A PLC timer begins timing for the star period (e.g., 10 seconds).
   
4. Transition to Delta: After the timer ends, the star contactor de-energizes and the delta contactor energizes.
   
5. Motor Runs in Full Load: The motor now runs at full voltage in delta connection.
   
6. Stop Push Button (STOP): Stops all contactors and resets the system.
   

This is the standard sequence used in most industries – from automotive plants to textile mills – to control heavy motors efficiently.

Required Components

Before programming, make sure you have the following hardware and software ready:

Hardware:

• 3-Phase Induction Motor
  
• PLC (e.g., Siemens S7-200, Delta DVP Series, Mitsubishi FX Series, Omron CP1H, etc.)
  
• 3 Contactors (Main, Star, Delta)
  
• Overload Relay
  
• Push Buttons (Start & Stop)
  
• Power Supply
  

Software:

Depending on your PLC brand, download the suitable software from PLCUnlock.com:

• Siemens STEP 7 MicroWIN V4.0 – for Siemens S7-200 PLC
  
• Mitsubishi GX Developer or GX Works2/3 – for FX Series PLCs
  
• Delta WPLSoft or ISPSoft – for Delta DVP Series
  
• Omron CX-Programmer – for CJ/CP Series PLCs
  
• Allen-Bradley RSLogix 500 or 5000 – for Micrologix and ControlLogix PLCs
  
• Pro-face GP-Pro EX HMI Software – for HMI control visualization
  

All these programs are available in unlocked versions to make your automation journey seamless.

Step-by-Step: How to Program Star-Delta Control in PLC

Let’s look at the programming logic step by step. We’ll describe it in a way that works for any brand of PLC software.

Step 1: Define Inputs and Outputs

Step 2: Create Latching Circuit

When you press Start (I0.0), it should latch the circuit so that the motor remains ON even after releasing the button.
You can do this by using a SET/RESET instruction or a self-holding contact depending on your PLC software.

Step 3: Add Star Contactor Logic

After latching, the PLC energizes Q0.0 (Main) and Q0.1 (Star).
When Star contactor is ON, the Timer (T1) should also start counting.

Step 4: Program Timer for Transition Delay

The timer defines how long the motor should run in Star mode before switching to Delta.
For example, set T1 = 10 seconds.

In Siemens software (MicroWIN), you can use TON (On-delay Timer) for this.

Step 5: Add Delta Contactor Logic

After the timer completes, Star contactor (Q0.1) de-energizes and Delta contactor (Q0.2) energizes.
Make sure to include an interlocking condition so both star and delta contactors cannot turn ON at the same time – this protects your motor and PLC outputs.

Step 6: Add Stop Button Logic

When Stop (I0.1) is pressed, all outputs (Q0.0, Q0.1, Q0.2) must turn OFF immediately.
This ensures a safe and complete motor stop.

Step 7: Test and Simulate

Before downloading to your PLC, simulate the logic using your PLC programming software:

• Siemens: Test with STEP 7 MicroWIN simulation mode.
  
• Delta: Use WPLSoft simulator to verify timer transitions.
  
• Mitsubishi: Simulate using GX Works2.
  
• Omron: Use CX-Programmer simulator.
  
• Allen-Bradley: Run test mode in RSLogix 500.
  

Simulation allows you to troubleshoot your logic before connecting to real hardware.

HMI Integration (Optional but Recommended)

You can enhance your system by connecting an HMI (Human Machine Interface). With HMI software like Pro-face GP-Pro EX or Weintek EasyBuilder Pro, you can display:

• Start/Stop buttons
  
• Timer countdown
  
• Motor status (Star/Delta)
  
• Fault indicators
  

This makes your system more interactive and professional.

Download HMI software from:

• Pro-face GP-Pro EX Software
  
• Weintek EasyBuilder Pro
  
• Delta DOPSoft

Advantages of Using PLC for Star-Delta Control

1. Precise Timing Control: PLC timers provide accurate and adjustable transition delays.
   
2. Flexibility: Modify parameters without rewiring.
   
3. Safety: Built-in interlocks prevent simultaneous operation of contactors.
   
4. Scalability: Easily expand for multiple motor controls.
   
5. Integration: Combine with HMI and SCADA for advanced monitoring.

Pro Tips for Successful Programming

• Always ensure star and delta contactors never energize together.
  
• Use retentive timers if you need the system to remember timing after a power loss.
  
• Label all your inputs/outputs properly for easier troubleshooting.
  
• Use simulation mode to detect logical errors before hardware testing.
  
• Keep a backup of your program after final testing.

Where to Get the Best PLC Software for Star-Delta Programming

If you want to practice PLC programming or create professional automation projects, you’ll need access to full-version software.
At PLCUnlock.com, we offer:

• Siemens STEP 7, TIA Portal, LOGO Soft Comfort
  
• Mitsubishi GX Developer, GX Works2/3
  
• Omron CX-One, CX-Programmer
  
• Delta WPLSoft, ISPSoft, DOPSoft
  
• Allen-Bradley RSLogix 500, FactoryTalk View
  
• Pro-face GP-Pro EX
  
• Fuji, Panasonic, Exor, Inovance, and LG PLC software

All versions are fully unlocked, easy to install, and ready for both learning and industrial use.

Conclusion

Programming a Star-Delta control using a PLC is one of the most important foundational exercises in industrial automation. It teaches you logic design, timer management, and safety interlocking – essential skills for any automation engineer.

By using brand-specific software such as Siemens, Mitsubishi, Delta, Omron, or Allen-Bradley, you can implement, test, and improve your control systems with confidence.

Visit PLCUnlock.com today to download any PLC or HMI software you need – all in one trusted platform. Whether you’re a student, technician, or automation professional, our tools and resources will help you unlock your potential in PLC programming.

Related Software Downloads

Enhance your learning with these guides and tools available on our site:

• Download TIA Portal V16 Full Version Free
  
• Download STEP7 MicroWIN V4.0 Siemens PLC Software
  
• Mitsubishi GX Works3 Free Download
  
• Omron CX-Programmer Full Version Free
  
• Delta WPLSoft Free Download
  
• Allen-Bradley RSLogix 500 Software
  
• Pro-face GP-Pro EX HMI Software
  
• Weintek EasyBuilder Pro HMI Software