What Is a Contactor?

This is the second blog post from the “star-delta starter wiring and PLC program” series. As I stated, my aim is to make this an easy to follow and enjoyable training experience so before diving into the wiring of a star-delta starter, I’d like to teach you a little bit about what a contactor is and how it actually works.

So, what is a contactor in electrical industries? In the video below, using a simple and effective animation, you’ll learn what the main parts of a contactor are and how it can help you to turn on and off the industrial equipment.

Let’s say you have a lamp that you want to turn on, to do that, you need to connect it to electricity. Once connected to electricity, the lamp will light continuously.

Now, if you want to turn the lamp on and off, what should you do? You can add a simple switch, which allows you to turn the lamp on and off whenever you want.

Now let’s say you have an electrical motor instead of the lamp. To turn the motor on, you connect a 3 phase power circuit to it.

If you want to be able to turn the motor on and off whenever you need it, just as you did for the lamp, you can add a switch here. This switch is similar to what you used for the lamp but there is a small difference. The difference is that this is an industrial switch. We call this industrial switch “contactor”.

A contactor is composed of two main parts: coil (or electromagnet) and contacts. When you connect power (electricity) to this coil, the coil is energized and creates an electromagnetic field around itself. This field causes the contacts to close which allows the current to flow from source to load.

So the contactor functionality is very simple. When the coil is energized and an electromagnetic field is created, the contacts will be closed.

As you can see in the diagram below, there is a button for the lamp that can be pushed to turn that on or off. But there is no button for the contactor. So the question that you may have here is that “how can I turn on or energize the contactor when there is no button to push?”

You can do this by connecting the contactor’s coil to a PLC output or any other type of controller.

Here is what you can do for the PLC to be able to energize the contactor’s coil: First, you need to connect a simple switch to the PLC input.

Next, using TIA Portal,  write a simple piece of code to energize the contactor’s coil whenever the start switch is press.

When you’re done writing the program, you need to download it to the PLC. By doing this the PLC can undestand what you want it to do with the input and the output. Doing this allows the PLC to know exactly what you want it to do because now it has the program.

Now you know how a contactor works.

As always — thanks for reading, watching and sharing. The conversations that happen here are true nourishment for our soul.

With tons of love,

The RealPars Team

By Shahpour Shapournia

By Shahpour Shapournia

CEO, RealPars

Last updated Oct 3, 2017

By Shahpour Shapournia

CEO, RealPars

Last updated Oct 3, 2017

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