Tuesday, November 10, 2015

Contactor Wiring Guide For 3 Phase Motor With Circuit Breaker, Overload Relay, NC NO Switches

In industrial system we use mostly three phase electric power for electric induction motors. A single phase induction motor can not do work as a 3 phase can done. For 3 phase motor we use some electrical devices for starting, off and resetting, magnetic contactor is one of them that's why today we disuse about contactor wiring with complete explanation. In 3 power system we use some devices between induction motor and supply which are a CB Circuit breaker, MC magnetic cont actor or motor stater, O/L overload relay and NC, NO push button switches for on/off and reset.

How To Do Contactor Wiring For 3 Phase Induction Motor With 3 Pole Circuit Breaker, Overload Relay, NO,NC Push Button Switches

In this tutorial post i will tell you about motor contactor wiring and it's diagram. But before we will disuse devises and working.

3 Pole Circuit Breaker CB

For 3P power supply we use to 3 pole circuit breaker for switching supply. Always use a CB before circuit wiring, from this you can make your circuit safe and we you will be able to switch off/on any time. You can also use 4 pole breaker, which is very best because you can control also the neutral wire.

MC Magnetic contactor

For 3 phase induction motor start/stop we use always MC contact or. It's is a type of electric relay which can switch the 3 electric connections easily. I also published post about motor starter working you can see on below links.
Click here for more information.

O/L Overload Relay

Overload relay is protective device which make safe our electric motor from burning during high current flowing to the induction motor. There are two popular types O/L relay which is thermal overload relay and Electronic overload relay. In this wiring diagram contactor, i shown thermal overload relay however soon i will make a diagram about electronic relay.

NC Normal Close Push Button Switch

For motor contactor wiring we use push button switches for switching on/off the motor. NC means normal close which means that this push button is normally in close circuit and when we push, it's make an open electric circuit. I show NC with red color button and NO with Green color.
For details Click here.

NO Normal Open Push button Switch

The Normal open S is normally in open electric circuit and if a person push this NO it's make NC circuit. For further information visit below link.
For more info click here.

MC Motor Starter Wiring Diagram With CB,MC,O/L, NO, NC

The symbol diagram is best but every one can't understand it easily that why i always focus on image+diagram which easy and simple to understand and good for learning. But you know that this diagram designing takes bag time from the time of symbol diagram. But i love my readers, as i am a student and struggling- for learning. I want to share all things which i learned.
Magnetic contactor relay wiring and circuit breaker , push button wiring method is simple. And i think that there is no importance to explain more after making diagram, however let's get a short tips journey.
For 3 phase motor controlling diagram and procedure, follow the below tips.
  1.  First of all wire the CB Circuit Breaker but do not switch On.
  2. Then Wire push button wiring O/L relay and MC coil, which we can called small wiring.
  3. Then wire the overload relay with MC.
  4. Then Do connection between CB and MC.
  5. Then do motor supply connection with Overload relay.
  6. Then connect the earth led wire to the motor body.
You can follow same method as i shown in below contactor wiring diagram for wiring 3 phase motor with circuit breaker, 3 pole motor stater and overload relay.

contactor wiring diagram

The New Diagram is best So use the New diagram Connection

contactor wiring diagram for 3 phase motor

In above contactor wiring diagram i shown 3 phase 440 volts 4 wire system. I take one phase and neutral wire for MC coil which 220V, but always wire your contactor coil regarding coil voltage / current requirements. If coil required 110V to 120V then provide 110 volts supply and if it is want 380 volts to 440V to energize then connect same required supply. The coil voltage cheat- is near- in coil supply terminal/connection so check it first before starting.
In overload relay we have to option which NC and NO. When the flow of electron is high ring- from it's value the NC points change its direction and make an open circuit or broke- the circuit. Which are shown in above image with 95-NC-96.
If you want to learn from symbol contactor wiring diagram then click here.

Message :

The above is example diagram of contactor wiring with overload relay, and i hope that this diagram help newbie very mush. But this is only starting and IN SHA ALLAH we will make more best contactor wiring and more tutorials for you.
Stay tune.... and keep visiting......


  1. 4 phase motor controller panel box full wiring diagram need.pls help

    1. Dear IN SH ALLAH i will make complete 3 phase 4 wire system panel box wiring.....

    2. hello i have 3 phase wiring in my house , i want co connect a 3 phase contactor in such a way that a hotel type key switch can control the contactor . when the keychain is removed the contactor goes off and power to house is cutoff. will the contacting coil work if one or two phases are off

  2. hi,
    u added two red wire through nc and no button with the overload. what is that for?

    1. It is not between nc and no. it is in nc to nc and when over current flow the overload relay will make an Normally open connection between these two nc points and current is stop flowing to contactor / stater coil.

    2. Thank you for your most valuable contribution to spreading knowledge. The pictorial wiring diagram is genius. Thank you.
      Deo Winter

    3. if there wering asked ATS to genset..thanks Sikandar Haidar..!!?

  3. Thanx Sikandar for the valuable information.

    can you show a Distribution Board Wiring For three Phase Wiring, with options for a couple 220v single phase connections.

    Example. I have a 3phase engine suppling power to a 3phase borehole pump/motor with a switch the one above in your example. But i want some single phase connections on the DB for
    my single phase power tools. e.g. grinder,drill and welding machine and light for the pump house. How do i connect up..



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  5. Hi, I enjoyed your work. What is the circuit diagram use to connect dispensing pump in petrol stations ?

  6. Hi, I enjoyed your work. What is the circuit diagram use to connect dispensing pump in petrol stations ?

    One, Timothy Obinna

  7. Hi! Great diagram! Thanks! Just one question...how would I wire up 2 on/off stations?

  8. DjazakaAllahu hayran bro ! May Allah bless you for your helping ! Keep it going. As-Salamu aleykum from Turkmenistan.

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