Magnetic Contactor

Magnetic contactor is common used in automation industry for motor control application.It is function basically like “relay”.The power source into the coil of winding,it like the solenoid operation.It can delivery a big ampere to  the loads and very long lasting and high durability.

When the power is “on”,it energized the coil and make plunger move and the switch contact is change from normally open to closed position.It allowed the current move from input terminal to output terminal.Then if we connected to the 3 phase motor,it will running :D

What is magnetic contactor?

This device have a several  component :

1) Main contact

– This contact used for switching the power supply to device to On or Off position.

2) Axillary contact

– This contact used for control circuit purpose.It have two contact :- NO ( Normally Open ) & NC ( Normally Close )

3) Power supply ( Coil )

– This is for energized the solenoid.It have in several range of power supply ( 24 VDC,24 VAC,110 VAC,240 VAC,415 VAC )

4) Auxillary  Block

-This is for additional for Auxillary contact ( NO or NC )


Typical applications for magnetic contactor:

• Electronic switching
• Resistive loads
• Non-motor-related inductive loads
• Disconnect switches
• VFD bypass/isolation


  1. zonaid hasan says:

    what mc rating would be for a 20 hp motor in star delta

    • Please refer to my last post,how to sizing magnetic contactor or Moeller website

      • zonaid hasan says:

        @ Mr. lemau.thnx for your reply.I would be using a star delta starter for this 20 hp motor(3p,440 v).so the current is lower in the first few seconds and later it would increase,as i know you are all aware of that .so what would be your suggestion about the size/rating of the MC’s for this two separate conditions of current .an example would help a lot

  2. Lulamile koloza says:

    dear sir/madam

    my question is that if the motor voltage on the nameplate is 525volts,then what voltage ratings must my contactor be for my main circuit and for my contol circuit on a strar delta,DOL and fowerd reverse starter?

    • Hi,if your Voltage rating is 525 Volt, you must use Contactor with 525 or 600 volt rating.You can refer manufacturing catalog of Contactor.

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