Industrial electricity

What is a Contactor?


The role of electricity in industry

Today, systems and equipment that work with electricity have made life easy and convenient for humans. But an important issue that should be addressed more is the security of electrical systems and appliances when in use.

Certainly, every person who works in the field of security of devices, equipment and electrical appliances is familiar with contactors and has full knowledge of their function. In fact Contactors are a part of systems that provide safety and monitoring in the efficiency of electricity and electrical equipment. Their function is disconnection and connection of electricity at the right time. Along with this article, in order to learn more about the contactor and its important parts, function and efficiency, join Sepyani Industrial Group.


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What is a contactor?

Contactors are an electromechanical switch and a part of the electrical monitoring and restraint group. which are used for electrical switching. Contactors are one of the most efficient electrical parts that are used in electrical circuits to disconnect and connect electrical circuits with high efficiency.

The contactor is a magnetic switch that, like normal three-phase switches, has 3 important contacts with the ability to connect systems and electrical appliances to the network, as well as a number of side contacts for the purpose of designing control circuits.

In order to explain how the contactor card works, it should be mentioned that their function is the same as that of a relay. but they will be able to transfer up to 12500 amperes. The contactor is mainly used in parts where there is a greater potential for transferring silane. Considering that relays are used for cases where less current is used. Relays will not be able to provide protection against short circuit or overload; But they are able to disconnect the connection during the antric time of the coil.

Static and dynamic sections:

The contactor consists of two E or U-shaped cores, one of which is static and the other dynamic. When the silane passes through the electromagnetic core, a magnetic field is created and the change in power created by the electromagnetic field determines the conditions of the contacts. Contactors are made in various types and energy capacities. Unlike the automatic switch, the contactor is not designed to disconnect the short circuit.

Contactors have several contact models based on usage and load, mainly open (NO) models. As a result, when the contactor coil is disconnected, the load is disconnected. But the contactor will be able to be designed for the tasks that are open or closed in the natural state. The most common function of contactors is to start, which is used to turn on and off systems such as motors, transformers, thermal operators, lighting, heating, etc.

Contactors will be able to handle a wide range of currents from a few to thousands of amperes and voltages from 25dV to thousands of volts. In addition, the sizes of these systems are in various sizes, from small and small handheld sizes to large sizes of one meter or several meters.

Contactor generating parts:

Before we review and explore what the contactor knife is like. You should consider what are the most important components of the contactor and what is the function and duty of each one.

Coil/electromagnet in the contactor:

This component of the contactor provides the driving force of the contactor that causes blocking. The coil is wound around an electromagnetic core and thus works like an electromagnetic magnet. It has two parts, one is static and the other is stable. The stable part is connected to the static part with a spring. This form causes the mechanism of spring deflection.

A rod called armature is attached to the fixed part. When the power of the coil is greater than the force of the spring, both contacts are connected to each other. When the power of the spring exceeds the force of the coil, the contacts are disconnected.

The contactor coil input can be AC or DC. This coil is branched from an external restraining circuit for the contactor, and its function is the antric of the electromagnetic core. The electromagnetic core material of AC contactors is made of soft multi-layered iron. This material helps to reduce the wastage of vortex fluid. In DC contactors, solid steel is the material for the electromagnetic core because eddy currents will not form.

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Contacts are responsible for transferring silane in the contactor. Various contact models are available in the contactor, including: side contact, electrical contact and contact spring. Electric contact has two different models, which include: static and stable contact.

In order to create contacts, it is required that the material contains high welding strength and stability and constant curvature stability. This material should also have acceptable stability and endurance against wear and tear and mechanical stress. In the case of high silane and DC, silver tin oxide is used, while in the case of low silane, silver nickel and silver cadmium oxide are used.


As its name suggests, it protects and maintains the internal parts of the contactor. It protects and maintains the contactor against contact with dust, polluted weather, explosion hazards and oil. It also prevents employees from dealing with contacts.

How the contactor works?

How does the contactor function? The operation of this part of the contactor is extremely easy and convenient. The fluid passing through the contactor energizes the electromagnet and antrics the electromagnetic core.

After that, the high power electromagnet creates a magnetic field. This causes the armature contactor core to move. And then the circuit between the static and dynamic contacts is completed by a normally closed (NC) contact, which allows the current to pass through the contacts to the load. When the coil is disconnected from the passage, the coil will carry the electric current and open the circuit.

Contactors will be able to open and close very quickly, therefore they have the ability to withstand larger loads. Because the contactors are designed to open and close the contacts at high speed, it is possible for the stationary contacts to jump due to a high-speed impact with the stationary contacts. A plug contact is used in a large number of contactors to prevent jumps.

Regarding the contactor, we need to know what the silane entering the contactor is. It is likely to be DC or AC (in various voltage ranges between 12VAC or 12VDC to 690VAC or 440VDC). A small amount of electricity is used by the contactor coil during its work. In order to reduce the amount of electricity drained by the contactor coil during operation, it uses economizer circuits.

Contactors containing AC coils are equipped with shading coils. Otherwise, they’re in trouble every time AC crosses zero. The shading coils will be able to delay the demagnetization of the magnetic core to prevent collisions.

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Application of contactor:

Contactors have various uses, the most important of which will be mentioned in the sequel of this article. You can join Sepyani Industrial Group to learn more about the use of contactors.

Lighting monitoring and control:

Contactors are mostly used for central control and monitoring of huge lighting infrastructures such as office buildings or stores. In order to reduce the use of electricity in the contactor coils, they use backup contactors that have two active coils. A coil, momentarily energized, blocks the power circuit contacts, which then remain mechanically blocked. The second coil unlocks Audiences.

Electric motor starter:

It is the most important contactor in starting the engine. Contactors are used in starting the motor in the form of Direct on-line or Star Delta with bimetal. The contactors will be able to operate as a magnetic starter. A magnetic starter is a device designed to provide power to electric motors.

This section contains a contactor as an integral part, while also providing protection against power outage, undervoltage and overload. Even though it can be found in our homes, it can be found inside the pump starter. Generally, in the motor starter circuit, they are used for switching purposes, including overload relays and short-circuit holding systems.

Switching capacitor banks:

In capacitor banks, capacitor switching contactors are used to change capacitors based on reactive energy needs. They are specially designed to control and monitor high pass currents that are formed during switching.

Misalignment of the backup contact and the main contact

The main contact and the backup contact of the contactor are similar from the foundation point of view. But they have different functions. The main contact is used to disconnect and connect the electric circuit with high energy. But the backup contacts have a monitoring function and generate an outgoing signal.

The difference between contactor and switch:

  • The contactors will not undergo mechanical erosion when disconnecting and connecting the contacts on each other, so their mechanical life span is longer compared to other switches.
  • Protection of systems by contactor is more necessary and safer.
  • Monitoring and remote control of devices by contactor is more economical and safer.
  • It is possible to connect and disconnect the user from different points through the contactor.
  • By designing a suitable circuit, you will be able to increase the speed of connection and disconnection of the circuit by the contactor.
  • When the power disconnection also disconnects the user circuit and needs a starter in order to restart; Therefore, the risks of unexpected connection of the system are prevented.

Difference between AC and DC contactor:

  • Contactors are designed for AC and DC currents. These two contactors also have distinctions; In the AC model, a short connecting ring is used to prevent the vibration resulting from the power frequency.
  • The number of pulses that this function will reach its maximum capacity and become zero is twice the frequency of the network. Therefore, when the size of the tensile force is greater than the resistance force of the contactor springs, the contactor core is abducted, and when the size of the tensile force is smaller than the force of the springs, the stable core will be released and return to its starting point.
  • As a result, there will be vibration and sound in the stable core. This high activity can be solved by a closed ring installed on top of the poles, which covers approximately one-half to two-thirds of the top of each pole, and does not eliminate its vibration. The function of this ring is such that, like the secondary winding of a transformer that is short, it will pass through the induced current and cause a branched magnetic jump in the core circuit.


To buy industrial parts such as contactors, you can visit our store and inquire about the current price and order foreign parts for import. To get more information, you can text us by What’sApp or complete the consultation request form so that our engineers will contact you as soon as possible. Sepyani Industrial Group is at your service with a team of experienced engineers.

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