Leader in AC/DC Surge Protection Device

Call us Now :

+86 18969702600

Email us now :


Contactor Types, Advantages and Applications

What is a contactor?

A contactor is an electromagnetic switch used to control high-power circuits. It is used to connect or disconnect the circuit. The electrically controlled contactor uses a power supply level that is much lower than that of the switching circuit. It is usually used to control equipment such as motors, and is used with large power supplies. Unlike some ordinary push button switches, contactors use electronic means to switch power circuits, which is more convenient and safer.


It can be divided into AC contactor and DC contactor according to the current it handles, and there are also other types such as power contactor, auxiliary contactor and vacuum contactor.

Ac contactor: A contactor for AC circuits that uses a mesh arc extinguishing device to handle the arc sparks generated by the switching circuit. Its components are an electromagnetic coil and a set of contacts. When the coil is energized, a magnetic field is generated that pulls the contacts together and the circuit is closed. When the coil is deenergized, the contacts separate and the circuit is broken.

DC Contactor: A contactor used on DC circuits that uses an arc extinguishing device to handle longer lasting arcs. It connects the moving contacts and the static contacts through the magnetic force after power is turned on, and they will separate when the power is turned off.

Power contactor: used in high power circuits. Usually have larger size and larger ratings, and have a more rugged housing, so they are often used in industrial applications to control motors and other equipment.

Auxiliary contactor: used to assist larger contactors. This type of contactor is smaller and usually used to handle small currents. It is often used in conjunction with another contactor. To distinguish it, it is not used to switch loads, but has some control functions or connection functions.

Vacuum contactor: It is characterized by the use of vacuum extinguishing arc. This type of contactor will be smaller and suitable for applications where space is limited. Superior to traditional contactors in terms of service life, size and environmental adaptability.

How does it work?

The working principle of a contactor is to use electromagnetic effects to control the closing and opening of contacts and control the switching of circuits.

Basic working process: After power is applied, the coil in the contactor will generate electromagnetic force to attract the iron core, thereby driving the contacts to move, causing the two contacts to close, and then the circuit is connected and the circuit is energized. When the power is cut off, the electromagnetic force disappears, the iron core will reset due to the spring, the contacts will separate, and the circuit will be cut off.

Advantages of Contactors

Contactors have several advantages over other types of control switches. They are more reliable, can handle high currents, are better suited for larger applications, and have a longer service life and do not require regular maintenance.

Contactors provide isolation between low-voltage control circuits and high-voltage power circuits, which improves worker safety and also protects load equipment from surge damage.

Contactors are important in industrial automation. They allow low-power switches to control high-power equipment, thereby realizing various machine functions, such as remote control and automated operation.

Contactors are available in various configurations and can be used to control different combinations of voltages and contacts to suit a variety of applications.


Contactors are mainly used in industrial applications for high power current control, such as Electric generator, lighting systems, power distribution systems and other applications.

Electric generator: Contactors are usually used to turn the motor on and off, and can also provide some additional functions, such as operating speed control and timing. Widely used in factory machines, ventilation fans and air conditioning systems, etc.

Lighting system: Contactors are also commonly used to control street lights, large lighting equipment, etc., and can also provide additional functions of scheduled on and off. They can centrally control lights and provide convenient settings management.

Power distribution system: Contactors are used to manage the flow of electric current. They can be used as remote control switches to systematize power and provide a more convenient distribution path.

Other applications: Contactors can also control transformers or some high-power load equipment.

The difference between contactors and relays

What is a relay?

A relay is a switch consisting of a coil, yoke, armature and contacts, used to open and close circuits electronically or electromechanically by using a small current to control a larger current.

Relays are commonly used in applications such as control panels and industrial automation to control smaller current values in a circuit. Also used to control multiple circuits with a single signal or to provide electrical isolation, a variety of relays provide solutions for each specific application.

The main differences between contactors and relays are load capacity, open/close contact standards, auxiliary contacts and various safety functions.

Load capacity: Relays are used to carry loads of 10A and below, while contactors can be used to carry loads above 10A.

Open/Closed Contact Standard: Relays are designed for use in both operations, depending on the needs of the actual application, while contactors are basically designed to operate in a normally open contact configuration only.

Auxiliary contacts: Contactors usually use auxiliary contacts to provide various additional functions, such as indicator lights on some machines.

Safety features: Since contactors usually carry high loads, they come with safety features such as spring contacts, arc suppression, and overload protection.


How to choose the right contactor?

Selecting the appropriate contactor requires confirmation of load requirements, load type, specific application and number of poles.

Load Requirements: Confirm the load requirements and purchase a contactor with an equal or higher current rating to safely operate the circuit. Voltage compatibility also needs to be taken into consideration.

Load type: Consider whether the load equipment is sensitive to current, such as sudden surges in current when some generators are started. It is more appropriate to choose a contactor with a current rating higher than the operating current.

Specific applications: Consider the operating frequency of the contactor and whether it is used for frequent operation. The environmental conditions of the application scenario, whether it is exposed to extreme temperatures, high humidity, or a large amount of dust.

Number of poles: The contactor can select the appropriate number of poles according to the specific application to control multiple circuits.

How long is the service life of a contactor?

Due to different types of contactors and different applications, the number of operations in the service life ranges from several thousand to one million. Some small contactors can operate more than 10 million times.

The biggest problem that affects the service life of a contactor is the frequency of use of the contacts. The higher the frequency of opening and closing of the contacts, the shorter the service life of the contactor. The arc generated during the switching process will cause burn marks on the contact surface and cause wear and corrosion on the contacts.

In contrast, isolating the arc or quickly switching contacts can extend the service life of the contactor.

Why does the contactor need to be replaced if it works?

If it is found that the contact point of the contactor is seriously blackened, loose or dented, it is recommended to replace it with a new contactor. Because these small problems can lead to subsequent dangers, the entire surface cannot be fully contacted, and poor contact can cause the circuit to overheat and damage the equipment.

Replacement of the contactor with a high quality and suitable one is necessary. All wiring and load equipment require stable and tight connections. If you have any concerns or needs about low-voltage electrical equipment such as contactors, you can contact Thor.