Transcript:
[0m:00s] Hey, I’m Mitchell. Welcome to another video in the RSP Education Series. This isn’t your average light switch. A contactor is the muscle behind industrial machines, designed to control massive currents with just a tiny signal. Want to know how factories start motors from hundreds of feet away? Stick around, because once you understand contactors, you unlock the power of automation. If you like this content and want more educational videos, please like and subscribe. This video is for educational purposes only. Consult a professional for your application. RSP Supply is not liable for any misuse of this information. With that said, let’s dive right in.
[0m:43s] So, what is a contactor? It’s basically a remote-controlled switch used to turn electric motors on and off. Think of it as a heavy-duty version of a light switch, but controlled by electricity instead of your hand. It’s built to handle large currents in motor circuits. Contactors are electromagnetically operated, meaning they use an electromagnet to open and close the contacts inside. The basic parts of a contactor include the coil or electromagnet, which activates when voltage is applied. This creates a magnetic field that pulls the contacts together. The main power contacts handle motor current—typically three poles for three-phase motors. There are also auxiliary contacts used for signaling or logic in control circuits. Finally, a spring mechanism opens the contacts when the coil is de-energized.
[1m:44s] Why use a contactor instead of a regular switch? Motors draw a lot of current, especially during startup. Contactors are designed to safely make and break high-current circuits quickly and reliably, reducing arcing. They can be controlled remotely from a PLC or control panel and easily integrate with overload protection, interlocks, and safety systems.
[2m:09s] In an automation setup, when a PLC or control system wants to start a motor, it sends a small voltage—like 24V DC or 120V AC—to the contactor coil. The coil energizes, creating a magnetic field that pulls the main contacts closed, allowing power to flow to the motor. To stop the motor, the control system removes the voltage, the field collapses, and the spring reopens the contacts, cutting power to the motor. On its own, a contactor doesn’t provide protection against overloads or short circuits. That’s where motor starters come in. A motor starter is a contactor combined with overload protection. There are two main types. The first is a direct-on-line starter, which applies full voltage to the motor and includes a thermal or electronic overload relay. The second type includes soft starters and VFDs, which limit inrush current at startup using electronic controls or multiple contactors.
[3m:16s] To bring it all together, a contactor is a remotely controlled powerhouse that uses electromagnetism to switch motors on and off from a distance. Built for heavy-duty performance, it handles high currents and integrates easily with PLCs and other control systems. While it doesn’t protect your equipment by itself, pairing it with an overload relay creates a full motor starter setup. Add a soft starter or VFD for even smoother motor control. Now that you know the basics, you’re one step closer to mastering motor control. For a full line of contactors and hundreds of thousands of other industrial automation products, visit rspsupply.com, the internet’s top source for industrial hardware.