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What are the differences between relays and contactors?

News | May 13,2023

Relays are used to control high-voltage circuits with low-voltage signals. They are commonly used to switch lights, motors, and other high-voltage loads. A relay consists of an electromagnet, a switch, and a set of contacts. When the electromagnet is energized, it attracts the switch, closing the contacts and allowing current to flow through the circuit.

Contactors are similar to relays, but they are designed for high current loads. A contactor consists of an electromagnet, a set of contacts, and a set of coils. When the electromagnet is energized, it attracts the coil, which closes the contacts and allows current to flow through the circuit.

Relays and contactors are used to control circuits. They are all activated by electromagnets. They are both commonly used in industrial and commercial applications and function almost identically.

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What are relays?

A relay is an electrical switch activated by a solenoid. When current is passed through the coil, the coil generates a magnetic field which is used to operate the switch. Relays are used in a variety of applications including automotive, industrial, and medical.

Relays can be used to control a variety of devices, including motors, lights, and solenoids. They are also used in computer networks to provide isolation between two parts of the network. In some cases, relays are used to protect sensitive electronic components from damage.

Relay Module Function

Differences between relays and contactors

Relays and contactors are two types of electrical devices used to control electrical circuits. They are both capable of switching electrical current on and off, but they differ in how they activate and deactivate. Relays are activated by electromagnets while contactors are activated by solenoids.

Much like a relay, a contactor is an electrically controlled switch. It uses a coil that, when energized, closes contacts that allow current to flow. The main difference between contactors and relays is the load they are designed to handle.

When to use a relay?

Using relays is beneficial in many situations. For example, if you need to control a lot of power with a small signal, or if you need to isolate two circuits, a relay might be the perfect solution. Relays can also be used to create time delay circuits or switch between AC and DC power.

Relays are typically used on circuits with a maximum load rating of 20 amps but are mostly not used on circuits requiring more than 15 amps.

Typically only used in single-phase applications
They are primarily used in low-voltage automation, control, and safety circuits, often for switching smaller electrical loads.
In many cases, relays have normally open and normally closed contacts
Smaller size.

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When to use a contactor?

A contactor is an important device in many industries because it provides a safe and efficient way to control electrical circuits. Contactors can also be used to control various other loads including but not limited to lighting, heating and air conditioning.

The contactors can be used to switch loads in the current range 20a – 12500A. It usually consists of three separate contacts and is designed for three-phase power applications.

You won’t usually find normally closed contacts on contactors, they usually only use one set of normally open contacts. Therefore, the function of many relays is more simplified in some respects.

In many cases, they also have auxiliary contacts that can be used to monitor the status of the contactor. For example, if a contact opens or closes.

In some cases (depending on the contactor) they can provide arc suppression, which increases the safety of switching high-voltage loads. However, they do not provide short-circuit or overload protection, and these features require additional equipment.

Advantages and disadvantages of relays and contactors

Relays and contactors are two types of devices that are used to control electromechanical processes. Both devices have advantages and disadvantages that should be considered when choosing which one to use for a particular application.

Relays are typically smaller and less expensive than contactors. They are also easier to operate and can be used to control lower-voltage processes. However, relays can only be used to control one process at a time, and they are not as durable as contactors.

Contactors are larger and more expensive than relays, but they can be used to control multiple processes simultaneously. They are also more durable than relays, making them ideal for use in industrial applications. However, contactors can be more difficult to operate than relays.


Although relays and contactors share some similarities, such as their ability to switch electrical loads on and off, they are designed for different applications and differ in size, power rating, switching capacity, contact material, control circuit, and cost All are different.

Knowing the difference between relays and contactors is important in choosing the correct device for a particular application.

Relays are typically used in low-power control circuits, while contactors are used in high-power applications such as motor control, heating and cooling systems, power distribution, and welding equipment. By choosing the right equipment, engineers and technicians can ensure that their electrical systems operate safely and reliably.

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