Safety and control are of paramount importance when it comes to electrical installations. One of the key players in electrical control circuits is the contactor. As either an industrial electrician or a student studying automation systems, knowing about a contractor is useful. This blog is to look at what a contractor is, how it operates, the types of contractors, and how it is commonly used. Additionally, we will also identify vocabulary words such as contactor relay, normally closed contactor, and contactor coil to link terminology into a whole understanding through real-life connections.
What Is a Contactor?
A contactor is an electrically operated switch used to open or close an electrical power circuit. It is very similar to a relay in the way that they both can utilize a low-power signal to control a high-power circuit. Thus, contactors are used for automation and are useful in everything from controlling industrial motors to lights. A contactor switch is a stronger-built switch than a conventional switch that can handle more current; that is why you find contactors in industrial electrical panels.
How Does a Contactor Work?
A contactor contains an electromagnetic coil (often referred to as a contactor coil) that, when energized, pulls a set of contacts together to complete a circuit. When the coil is de-energized, a spring returns the contacts to their original position
Contacts can be:
- Normally open (NO): Open when the coil is off, closed when energized.
- Normally closed (NC): Closed when the coil is off, opened when energized — also called a normally closed contactor.
Contactor vs. Contactor Relay
While the terms are commonly used interchangeably, there is an evident distinction:
- A contactor relay is generally applied to lower current applications, primarily for control signals.
- A motor contactor, however, is designed to suit controlling higher power applications, such as switching motors, heaters, and lighting.
Both are important tools in electrical supply networks and control panels for electrical contractors.
Varieties of Contactors
Contactors come in different types, each suited for specific applications:
- AC Contactors are suitable for alternating current systems and are commonly used in residential and commercial installations.
- DC Contactors are designed for direct current systems and are built to manage arcing, which is created by DC loads. DC contactor applications can be found in such things as battery systems and solar power systems.
- 24 Volt Contactors These low-voltage contactors use 24V DC or AC signals to activate the coil.
These are often found in automation panels and HVAC systems.
Applications of Electrical Contactors
Electrical contractors are widely used in almost all industries. Some common applications include: Motor starters:
- A motor contactor is the primary device in motor control circuits.
- Lighting circuits: Switching on large lighting loads in commercial buildings.
- HVAC systems: These are used as automatic control devices for compressors and fans.
- Industrial equipment: Automating conveyors, pumps, and heavy machinery.
Professional electricians use contactors for safe and reliable control of high-current devices.
Why Electricians Use Contactors
Commercial and industrial electricians use contractors for multiple reasons:
– To switch heavy loads remotely
– To wire safety interlocks and automation
– To provide overload protection to circuits (with overload relays)
They are an integral part of modern electrical installations and control systems.
Conclusion
A contactor is much more than an on/off switch. It enables the safe and automated control of power circuits on residential and commercial scales. Whether you are using a 24-volt contactor, DC
FAQ
What is a Contactor and what does it do?
A contactor is an electromechanical device that allows a low-voltage control signal from a PLC to safely turn high-voltage equipment on and off.
Why not connect a motor directly PLC output?
You cannot connect a motor directly to a PLC output because PLCs are not designed to handle the high current and voltage needed by motors. Doing so could damage the PLC. A contactor acts as a “go-between,” allowing the PLC to control large electrical loads safely.
How does a contactor work?
When energized by a control signal, a contactor has a coil that creates a magnetic field. This field causes the internal contacts to close, allowing current to flow to the motor or other device. The contacts open when the coil is de-energized, stopping the current flow.
What is the difference between a contactor and a relay?
Both devices use a coil and contacts. A relay is used for low-voltage, low-current applications like lamps, while a contactor is designed for high-current, high-voltage loads like motors.