Magnetic Contactor | Meaning, Types, Parts and Functions [Updated 2020]

By October 16, 2019Uncategorized
What is a magnetic contactor

What is Magnetic Contactor?

Magnetic contactors are the same as the electrical relays which are used in a number of electric motors. Magnetic contactors are used in the electric motors to balance the change in frequency of the motor or the state of the motor which can be termed as the switching of the motor from ON and OFF state. The change in frequency of the motor is due to the different parameters of the power sources which are direct power sources and due to the high load of electrical motors. Magnetic contactors act as a safeguard to protect the power supply and the motor. Magnetic contactors are sometimes considered as circuit breakers due to their similarity of shape with the circuit breakers but their functionality is different than that of circuit breakers. When the circuit between the motor and the power source is in short state the connection is cut off to safeguard the appliance. The magnetic contactors can be easily removed from the motors and the work on the motor can be performed easily. With the removal of the magnetic contactor from the motor, the possibility of live current passing to the motor is reduced to 0%. Relays and magnetic contactors are taken as the same equipment at the industrial level but there are a lot of differences between the relays and the magnetic contactors. Relay is used for loads up to 10A or less than 10A whereas a magnetic contactor is used for loads greater than 10A. Relays are typically used in single-phase appliances whereas a magnetic contactor is used in three-phase appliances. Relay has a common contact for the connection to the appliance while the magnetic contactor has 2 poles for its connection with an appliance.


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Magnetic Contactor Types

The main categories in which the magnetic contactors are classified are the ac contactors and the dc contactors. 

There are a number of magnetic contactors which are used at every level with different appliances such as:

  1. Magnetic starter.
  2. Reversing starter.
  3. Star-Delta starter.
  4. Mercury contactor.
  5. Vacuum contactor.
  6. Mercury-wetted contactor.
magnetic contactor types

magnetic contactor types

Magnetic Contactor Parts

The magnetic contactor has three main parts/components. The current in the magnetic contactor is carried out with the contacts. The contact includes different contacts like power contacts, contact springs, and auxiliary contacts. The circuit of the magnetic contactor is enclosed in an insulating material like Nylon 6, thermosetting plastics and Bakelite. The circuit is enclosed for protection in case of touching. The electric arc which is the main part of the contactor is moved by the blowout coils in case of a magnetic blowout. As an additional circuit, sometimes the economizer circuits are also included in the circuit of the magnetic contactor. This economizer is used to lower the power required by the magnetic contactor to reduce the coil current in the closed state. Economizers are usually used in the dc contactors coils and on large ac contactor coils.

Magnetic Contactor Functions

The magnetic field is generated by the electromagnet in the magnetic contractor when the electricity starts flowing in the magnetic contractor. The magnetic field created is a strong magnetic field that pulls the iron core of the magnetic contractor in the coil and as a result, an electric arc is generated. The electricity is passed into the magnetic contractor in this manner. To stop the functionality of the magnetic contractor it is simply pulled off from the device it is attached with. When there is no electrical current in the magnetic contractor, the connection of the core with the coil is also disconnected and the circuit connection is broken. 

Magnetic contactor functions

Magnetic contactor functions

How to choose a magnetic contactor?

The right decision for a magnetic contactor must be made to select a suitable contactor for the motor. The three things which should be considered while selecting a magnetic contactor are as follows:

  • The utilization category.
  • Motor’s inrush current. AC1, AC3, kW/HP rating.
  • The site electrical supply voltage.

These three parameters should be considered while selecting a magnetic contactor. 

How to choose the right magnetic contactor

How to choose the right magnetic contactor

Whereas the two steps while selecting the right contactor for a specified motor are:

Step 1: Gathering correct information about the motor.

Step 2: Extracting the right information from the right datasheet of the product.