Wednesday, April 15, 2020

DOL Starter Wiring Diagram 3 Phase Motor

We use three phase motor mostly in many places, in this post you will learn the dol starter wiring diagram 3 phase with complete circuit breaker, contactor and overload relay diagram with step by step. We required some electrical things for three phase motor wiring which are below.

3 phase induction motor
3 core electric cable
Three phase 4 wire system supply (three phase and one neutral)
A circuit breaker
A contactor or starter
A overload relay
and flexible wiring cable for controlling wiring
Normal close push button
Normal open push button

Before we starting talking about the wiring and wiring diagram, first we disuse the above substance . We required 3 core cable, a three core cable is a cable which have internal three electric cable which mostly in red, yellow and blue colors. The three phase 4 wire system supply means that we need 3 phase electric supply and one neutral wire. Note that we use the neutral wire for contactor coil wiring which we called the control wiring.
We also required the circuit breaker which are 3 pole circuit breaker or circuit breaker which can cutoff the 3 electrical connection in same time.

Normal close push button (NC) means that we need a push button which is normally have close electric circuit and when we push it then the button switch off the connection or change to the open electric circuit.
Normal open push button mean that we need a push button which have a open electric circuit in normal state and when we push it then it's change to the close electric circuit.

Dol Starter wiring diagram for three phase motor

To wire a 3 phase motor the first thing to wire is a circuit breaker which is disconnect and connecting point then we will get the supply from circuit breaker and connect supply to contactor or starter and then to overload relay. We connect the circuit breaker, contactor and overload relay in series between electrical supply and motor as shown in below diagram.

dol starter wiring diagram 3 phase
Contactor and Overload Relay Wiring

In a contactor we have a magnetic coil which is use for switching. We have also NC and No point in a contactor which we can use for many connections. In overload relay we have an input and output points. In normally overload points have a close electric circuit between point but whenever the ampere or load is getting high the overload relay switch off or make an open electric circuit between these two point or connection. So we wire the overload relay in series between the contactor coil current.
So for contactor wiring first of all connect the neutral wire to contactor coil first terminal and then connect a wire from the one output terminal of circuit breaker which is opposite or phase current for contactor coil. In this process the control wiring which contactor wiring is also control by breaker and when we switch off the breaker, then contactor will stop working auto.
The control wiring wire which connect from the breaker output terminal will goes to the NC push button and then from NC push to the overload relay and NO push button as shown in above diagram. Then we connect a wire between the 2nd terminal of overload relay and this wire goes to the NO point of contactor and then from NO point wire is goes to the 2nd terminal of contactor coil.
Then in last we connect a were between NO push button switch and contactor 2nd terminal of coil where we connect the phase wire of contactor as shown in above diagram. And this wire connection is called tech current.
Final word
Note that in all wiring use the best quality breaker, push button switches, contactor and overload relay. If your overload relay in not good then it will be not trip and if the overload relay does not trip or not switch the point then it will be case of your motor burn. Note that do all wiring control able from circuit breaker as I shown in above diagram.
Note that always connect the earth wire to motor, and adjust the overload relay ampere by using the adjustment switch.

I spend more than 2 hours on this article writing and designing DOL Starter Wiring Diagram 3 Phase Motor diagram, so if you learn some important things then it's your responsibility to share. Now if you have any question regarding the 3 phase motor wiring diagram then you can ask me in below comment section.


  1. All your posts are knowledgeable , keep it up bro

    1. thanks dear for liking our posts............

    2. salaams, you make it so simple to understand, thank you

    3. salaams, you make it so simple to understand, thank you

  2. Thanks a lot for shearing your valuable knowledge.

    1. Thanks for liking our post...... I Always try my best post best articles about EEE Technology.
      IN SHA ALLAH soon i will publish my new websites which help you more in electrical technology learning.......

    2. kindly do.i have learning alot from you Haidar.Many blessings

  3. Hi bro,
    will you please brief expalanation about wiring of overload relay using contactor

    1. Dear soon i will write about this overload relay wiring using contactor.

  4. hello brother
    Your article is very helpful to me.i really appreciate your work brother.
    May GOD bless you.
    I have a scenario in which i have a 3-phase motor of 7.37hp, 7.9A & i want to connect an overload relay & relay contractor to this motor.
    Brother can you please tell me which contactor and overload is suitable for my scenario?
    I will be very thankful to you for this favour.

    1. Dear your motor is 7.37 HP so if the voltage is 440v then your motor will get 11 amps. But you said that your motor getting 7.9 amps on running mode. So regarding your data 7.9x2= 15.8 contactor for this motor but some time voltage can be high or low then we plus the 20% extra
      So 15.8x20/100 = 3.16
      So 15.8 + 3.16 = 18.96
      So as 18.96 contactor not avilable in market then you can use 20 or 22 one th contactor for your motor.
      So the next thing what is amps of relay for your motor. Use an overload relay which can word up to 12 amps. For example if your overload relay is work form 5 to 12 amps. Then set your relay amps on 9 amps.
      If you need more help then you can ask me again.

  5. asslam alaikum bro.. jazakallah for your more information about electrical.. ji my question was how to select the MCB for control panel?

  6. Wonderful article. Really informative. Keep up the good work. Kindly assist me on how you set the overload relay. Thank you.

  7. I truly appreciate this post. I’ve been looking everywhere for this! Thank goodness I found it on Google. You’ve made my day! Thanks again..