Star delta motor connection

147 Comments / Electric Motor

Star-Delta Starter Motor Connections: Understanding the Basics

When wiring a motor for a Star-Delta Starter, it’s crucial to ensure the motor has 6 cables from the control panel and 6 terminals on the induction motor labeled as U1, U2, V1, V2, W1, W2. Proper wiring and understanding of the Star-Delta Magic Triangle are essential for ensuring correct motor operation and avoiding costly mistakes.

This guide provides step-by-step instructions to simplify the process, ensuring you can wire the motor connection confidently and correctly.

What is a Star-Delta Connection?

The Star-Delta Starter is a widely used motor control method for reducing starting current and torque. It requires precise wiring of the motor windings to achieve the desired operation.

The Star-Delta Magic Triangle is a helpful reference tool that illustrates how to connect each motor winding to the correct terminal for each phase. This triangle diagram is essential for understanding:

  • The correct phase alignment.
  • Cable terminations to the appropriate terminals.
  • Motor rotation direction (clockwise or anti-clockwise).

Why the Motor Nameplate Matters

Important Note: Always refer to the motor’s nameplate to confirm the winding numbering and motor connection details. Different manufacturers may use different numbering systems, so it’s critical to verify this information to avoid incorrect wiring.

Understanding Star-Delta Phases and Terminals

To wire the motor correctly for a Star-Delta Starter, follow this terminal-to-phase mapping:

  • Red Phase: U1 and W2
  • Yellow Phase: U2 and V1
  • Blue Phase: V2 and W1

The above mapping ensures each phase is correctly connected. To make things easier, let’s look at an example.

Example of Motor Wiring for a Star-Delta Starter

Follow these steps for wiring the motor:

  1. Match Each Phase to the Correct Terminals: Use the color codes (Red, Yellow, Blue) to connect the motor windings:
    • Red Phase → Terminals U1 and W2
    • Yellow Phase → Terminals U2 and V1
    • Blue Phase → Terminals V2 and W1
  2. Check for Motor Rotation:
    • For clockwise rotation: Connect the phases in the sequence Red, Yellow, Blue.
    • For anti-clockwise rotation: Swap two phases (e.g., Red and Blue). The sequence becomes Blue, Yellow, Red.
  3. Test the Wiring: Once the connections are complete, test the motor to ensure it operates smoothly and rotates in the desired direction.

Adjusting Rotation Direction

Changing the motor’s rotation direction can be done easily at the Delta Contactor. To switch between clockwise and anti-clockwise rotation:

  • Swap two phases (e.g., Red and Blue) at the contactor.
  • Ensure that all connections are secure before restarting the motor.

For a detailed guide on changing the motor rotation, refer to my next post.

Star-Delta Wiring Diagram

Refer to the Star-Delta wiring diagram for a complete understanding of how to connect the motor:

  • Control Wiring: Explains the connections between contactors, relays, and timers.
  • Power Wiring: Shows the main power connections to the motor and terminals.

For a comprehensive Star-Delta control wiring diagram, see my previous post on Star-Delta diagrams.

Conclusion

Wiring a motor for a Star-Delta Starter may seem complex, but it becomes manageable once you understand the Star-Delta Magic Triangle and follow the correct phase-to-terminal mapping. Always double-check the motor nameplate for winding numbering and ensure proper connections to avoid issues during startup.

Key takeaways:

  1. Use the triangle diagram as a reference.
  2. Follow the phase color codes (Red, Yellow, Blue) for terminal connections.
  3. Adjust rotation direction by swapping two phases at the Delta Contactor.

If you have any questions, suggestions, or need further clarification, feel free to drop a comment. Let’s share ideas and improve our understanding of Star-Delta Starters together!

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147 thoughts on “Star delta motor connection”

  1. BHARGAV

    DER SIR
    PLS REPLY ME FORMULA OF SELECT CONTACTOR & OVERLOAD REALY FOR STAR DELTA AND DOL STARTING.
    THANK YOU

  3. Sinnadurai Sripadmanaban

    Please give the curve showing the current surge (current vs time) during change-over fro star to delta as well as the current vs time curve if the same motor is started in direct on line method, in the same graph sheet. Also please give korndorfer type connection(with transition resistors)-for no break to avoid current surge.

  4. Gaurav Khanduja

    In Dol Starter Connection Relay Range Is according to motor Full load Current I= P/1.732 * V(415) * Cos $( .9)

    In Star delta Starter Connection Relay Range is According to Motor Phase
    Current I= [P/1.732 * V(415) * Cos $ (.9)] * .58

  5. Venkatesh

    Hello sir ,
    I’m having a small dounbt , in terms of converting a star winded motor to a delta winded .. motor was labelled as star rated in the motor name plate. so pls tel me is it possible to change the star winded to a delta winded ??

  6. lemau

    If you want run the motor using star delta starter,u must take off all cooper bar at terminal of electric motor.so no connection of star or delta.
    MAKE SURE : The motor design is DELTA connection only for star delta starter.if you used motor design STAR connection,your winding will burn out :D

  7. mukul

    sir ,i dnt get my ans of qus yet
    my problem is that whn motor comes to delta contactor the motor stops wht cn be the reasons behind this

  8. lemau

    mukul,please check your power supply wiring for motor terminal.make sure ur 3 phase wiring from delta contactor to motor is correct.

  10. lemau

    Time setting for change over is so subjective,it depend on load and inertia.Theoretically star change to delta when it reach 80% of full speed.from my experience,i setting around 10 sec to 15 sec maximum.

  11. zonaid hasan

    hello,
    i have a 20hp motor(20*746 watt=14920 watt).it requires a star delta control system.what should be the three MC ‘s rating.as two MC’s will switch operation,their ratings will be different?plz help me out with this MC’s ratings for this 20hp

  12. lemau

    First, you must know the Full Load ampere for your motor.
    FLA = 14920/(415*1.732*0.9)
    FLA = 23 Ampere

    So for MAIN contactor
    = FLA / FLI
    = 23 ampere

    For DELTA contactor
    = FLA x 0.58
    = 23 x 0.58
    = 13.4 @ 15 ampere

    For STAR contactor
    = FLA x 0.33
    = 23 x 0.33
    = 7.6 @ 8 ampere

    Please used AC 3 rating for contactor..please refer my last post about magnetic contactor sizing

    NEMA CODE :
    430.22 (C) Wye-Start, Delta-Run Motor. For a wye-start, delta-run connected motor, the selection of branch-circuit conductors on the line side of the controller shall be based on the motor full-load current. The selection of conductors between the controller and the motor shall be based on 58 percent of the motor full-load current.

    why multiply with 0.58?

    The Star/Delta starter is manufactured from three contactors, a timer and a thermal overload. The contactors are smaller than the single contactor used in a Direct On Line starter as they are controlling winding currents only. The currents through the winding are 1/root 3 (58%) of the current in the line.
    There are two contactors that are close during run, often referred to as the main contactor and the delta contactor. These are AC3 rated at 58% of the current rating of the motor. The third contactor is the star contactor and that only carries star current while the motor is connected in star. The current in star is one third of the current in delta, so this contactor can be AC3 rated at one third of the motor rating.

  13. manoj bhangale

    Hi,
    Please give me control circuit dia. with explanation of star-dalta starter.

  15. B.Srinivasa Raju

    I want star delta connection from starter in side terminal to motor terminal box with colour code

  16. lemau

    I already explain in my post..you just follow the wiring diagram for power circuit with color code..
    thanks

  18. NIRMAL FERNANDO

    DURING OPERATION OF STAR DELTA STARTER , 7.5KW MOTOR FOR STELL BAND SAW FOR LOGS SLICING FOUND BURNING OF DELTA AND STAR CONTACTS POINTS.OBSERVED THAT O/L IS OPERARATING.HOW TO OVER CPME THIS PROBLEM?

  21. IRSHAD AHAMED

    respected,

    i have a problem for start delta moters pls wright a good solition.
    probleam as
    when moter changed star to delta pocition it s gosse to trip main braker
    i checked panel first with out moter star delta condecter working good but when i connect moter terminal it s triped main
    when its run star it is ok its happen delta condector catiching time only
    so pls ans me what can i do the next step
    i checked moter wiring with megeer ther no rong simtems
    so pls wright good solition
    thanks

  23. Sadoon

    Dear Sir,

    really appreciate your efforts explaining in details. I just have small comment on the picture above (wiring connection), you may notice that there should be V2 instead of U2 of the blue wire coming from the delta contactor.

    Thank you

  24. Sadoon

    Dear Sir,

    can we have the same explanation on Auto-trans starter used in motor.

    thank you

  28. Mazhar

    Dear Sir;

    I saw ur web side it’s very awesome and grate, the way u explains is awesome and to point also. I love ur way. Dear sir I join mine life first job as electrical tech. I am new in plant. I am working at wharf area. My boss told me to make a presentation on Star and Delta, I need to know what I tell him in this topic, he says I need mathematical equations also and explanation and trouble shooting, what problem it can comes, how to tell without name plate, is it delta or star connection? in any motor. We are normally using 400v and 3 phase motors at every place. Need ur guidance to make best presentation.

    Will be looking forward for ur kind reply.

    Tc sir
    God bless u

    Thanks
    Mazhar

  29. onyx

    i would like to ask regarding the current above the two contactors namely main and delta when running operation.somebody told me that the above of these contactors have the same current.and the current under these contactors is less than the above.He is trying to say that the above current are the line to line currents while under the contactors are per phase currents.We are arguing the size of the conductors above of these two contactors, namely the main and delta contactors. I beleive that the above of these contactors are still in the per phase condition. The point were the two line 1 e.g. line 1 of main and line 1 of delta connected or joint,this is were the line to line condition.
    I hope you will give me clarifiacatioin regarding this matter.
    thank you

  30. Godswill Onwusoroaka

    i connected a 110kw of motor to star-delta but the speed is seem to be slow, what is the problem

  32. Dancan

    i took my stardelta motor for rewinding,when it came back the terminals were not labelled.Please help me to identify the U1 V1 W1 AND W2 U2 V2 using multimeter.
    Thanks
    Dancan

  33. lemau

    Dear Dancan,
    Use your multimeter and select continuity to checked pair or motor terminal.If buzzer beep that mean it the pair for the winding connection.

    U1 = U2
    V1 = V2
    W1 = W2

    i hope it answer your question….

  37. men

    please help me identify w/ch type of 3phase motor should i use the star-delta contol.i’ve seen motors having 220/440/3ph and 660/440/3ph.both are Y/D.which one is for Y-delta starter,or both of them are applicable,or not for such control wiring? thank you and hoping for further knowledge regarding this matter.

  39. Lim KB

    I have a problem when i connect to star-delta connection.
    The motor is 7.5kw.
    When i connect into star-delta, it run well in abt 8A, everything seem OK but when i leave it for one day (the motor is running with 24hr timer with 4hr run and 4 hr rest cont.), the contactor burned. I already check all wiring mega OK, component OK, my contactor with 12A i even change to 20A (incl MC, Star & Delta contactor) but it still burned. the change over relay is working well also, i set it abt 5-10 sec for change over.
    I feed up and change it to run in DOL, it work properly and have no problem with the same 24hr timer although earlier i suspect the 24hr timer problem make it start-stop too many time.
    I doubt is it the motor problem (let said if coil less or something related to star/delta running not enough speed when change over) will cause this matter which is abnormal for me.
    However, there are 3 set of motor with same size that i have the same problem with it.

    Anyone can help to answer me?

  40. jackie

    dear sir,
    surley it is possible to swap 2 phases over on motor connection box?
    instead of delta contactor

  44. fayyaz

    what connection shown for motor for starter is ok but to change direction just changingtwo clourof delta contactor will notwork i ids agree with you.just go throw the circuit.

  45. fayyaz

    just see due to this one winding gets connected in same phase i mean for ex. w1 is connected to red
    w2 is alsoget conectedto red.

  46. fayyaz

    see reason to stop motor in revers direction in delta connection is the one winding is getting connected in same phase.

  47. dinesh kumar

    hi i have i submersible motor,for that we r using DOL starter.now wats d problem is as d motor is immersed in the borewell we cannot hear d sound,so sometimes we forget to turn off d motor,so i hav planned to connect a buzzer with d starter,so whenever i turns on d motor i should hear some sound.

  50. lemau

    Hello..
    roughly description :-
    Relay : Normally in small size and for small application.Common used for control circuit or application.power supply range : 12 DC – 240 VAC

    Contactor :Have several type and size.Normally use for power control such as motor starter and power supply distribution for internal used.Rating size for contactor depend on kW or Full load ampere.

  51. fakansa boru fakansa

    iam greatly informed on your elaboration on electrical issues. pls sir can give me a detail explanation on how to wire a three phase capacitors to a three phase motor star delta starter panel

  52. fakansa boru fakansa

    I like the way you elaborate on electrical issues. Please,can you tell me how to connect three phase capacitors to a 30KW three phase motor in the star delta starter control panel

  53. Anil Paul Jacob

    Fakansa, There are capacitor banks which can be used on electrical networks with induction loads (motors). in this, APFCR (auto power factor correction relay will take care of capacitor selection = number of capacitors required for power factor correction will be selected by APFCR by its own. In your case you need to connect only one capacitor to the 30 KW motor. You can connect the capacitor through a contactor with required ampere capacity. and this contactor can be switched on manually after starting of motor. in another option you can control the contactor for the capacitor through a timer (making on delay after the motor running in full speed) to avoid the surge current.

  54. Anil Paul Jacob

    you have a problem in power wiring either in panel or in field wiring …. or check the contactors for the damaged contacts

  55. alexander

    Sir, How we will size the cable if we are using double supply cable for wye-delta pump motor

  57. lemau

    HI Anil,
    Thanks for your answer…it detail and easy to understand…i`m very appreciate with your input and shared some knowledge..

  58. AK Majumdar

    I have two motors each capacity 110KW 440V pf.75. Two motors simultaneously drive a fly wheel through pulley. Weight of Fly wheel is approx. 16T and dia. 3Meter. These motors have Star/ delta connection. Both motors start together. What should be the star to delta time set.

  59. lemau

    Hi AK Majumdar,
    This is a popular question for star delta starter.Ok from my experience,to setting the timer from star to delta,we cannot get the perfect time but we can used 2 types of measurement to get approximate time (second ).

    1. Use the clamp on meter ( analogue ) : Get information for motor Full Load Ampere(FLA),measure the ampere during star and set stop watch.Stop the watch and see the time when ampere reach 80 % of motor FLA.Use the time to setting your timer.

    2) Use the RPM meter : Get information for motor RPM speed.Use the RPM meter to measure motor RPM and use the stop watch to get a how many second that motor achieve 80% of RPM during star.Use that time to setting your timer.

    Typical times for Star Delta starter timer is around 10 until 25 seconds…but its depend on load.I hope this technique can answer your question.Please read my post about How to set timer for change over of star delta starter

  60. Siva balan

    Dear sir,

    I would like to know how to terminate the star-delta motor. We are using Crompton Greaves(110KW) motor. Kindly help me by giving the detailed termination detail’s for the star delta motor.

    Thank you

  61. lemau

    Hi Siva,
    I already explain how to connect power supply for star delta motor..please refer the wiring diagram at the bottom post.

    Red Phase from Main contactor : terminal U1
    Red Phase from Delta contactor : Terminal W2
    Yellow Phase from Main contactor : Terminal V1
    Yellow phase from Delta contactor : Terminal U2
    Blue Phase from Main contactor : Terminal W1
    Blue Phase from Delta contactor : terminal V2

  62. Habeeb

    Hi sir
    I just want to know that is there any problem if a 3 phase motor connected only with star connection( I heard that the star connection only for starting the motor ) So please confirm .

  63. lemau

    Hi Habeeb,
    You can use DOL or VFD starter if connected motor for star or delta connection.But make sure your motor voltage is suitable with star or delta connection.please refer to your motor name plate.

  64. mahesh deshmukh

    Hi sir,
    I want to know that why we interchange the two phase in star delta starter?what is the purpose of that?

  65. sumith mohan

    i have a issue with star delta starter.

    my delta is starting first then switches to star after the relay timer

    what may be the problem?

    i have checked the control schematic, and it is proper.

  66. Abhishek

    In star delta control circuit or DOL circuit can i interchange start push button to stop push button ?

    I think we can changed it….but we can’t apply because of IEC Standards.

    If we can not change control circuit why we can’t do ????

  67. Mr.Gururaj Deshpande.

    I am basically an electrical engineer working in Pharma company in India.
    I am stuck-up in designing power supply alternative to already installed maintenance-. free Battery.
    A deep freezer running on normal Single Phase power supply has Operator’s panel & display where the temperature is displayed & temp & alarm setting can be modified.
    Naturally when this power fails (even for short duration) of ONE minute, this equipment shuts down.
    During this period, in order to the DISPLAY to show actual temp. DISPLAY is powered by a battery.
    Rating of Battery is: 8Volts, 7 AH.
    Now I want to replace this Battery with a A.C power Supply & provide UPS Power to this NEW power supply to ELIMINATE the battery.
    How to decide about the current capacity of this power supply?

  68. simret

    hi, i want to ask how to know circuit breaker size current calculator for 3 phase ,380 volt ,20hp delta connection motor

  70. sreeraj

    check the star delta contactor and main contactor connection and motor connection and power supply also

  71. Aditya Sarma

    helo sir how to calculate the capacitor and relay for an three phase submersible motor for example i need to install a capacitor for 110 hp motor how can i choose the right one

  72. Muhammad shahid

    dear.
    slection of m.c and over load depend on ampere of motor for exp motor load 10 A then m.c amp 20 and o.cr is 10 a

  73. ABDUL HAFEEZ AKHTAR

    Please tell why in star connection current is one third than delta connection for same motor.

  74. Moses Mkangama

    I wants you to help me on how i can determine over-load setting for three phase ac motor star/delta,three phase DOL starter & single phase motor connected to 380 volts,50 volts.

  75. yikunoamlake haile

    hi my name is yikunoamlake haile.I live in Ethiopia and I am so interested by your work I need to learn about industrial electricity so I am electrician so please support me as you or the company need.

  78. Penuel

    hi
    I have a problem with my circuit, on star am getting a low amp reading. and on delta its high and the motor is over-heating. i have checked my connections, winding’s and followed the u1w2/v1u2/w1v2 connection. i have wired thousands of circuit but this one is giving a challenge. suggestions are welcome

  79. Daniel

    Hi,Dear Mr/Mrs
    I have a quastion about Delta &Star connection.Well 37kw motor(nameplate) 380/660v Dela and the voltages supplier is 380 v. Now does it logical to run motor with Delta &Star.On the contrary , 37kw 380/660v Delta /Star runs with just Delta connection.
    I am looking forward hearing from every one.
    Best Regards
    Daniel

  83. amol

    dear sir,
    plz suggest me control wiring diagram for contactor coil voltage 110v ac…I need to start &stop 30hp motor by start delta logic….Is it neccessity of step down transformer??? plz help me

  87. b k malviya

    I have to provide a power capacitor to a 30 HP motor having star delta operation and the three contactors for it. I do not have a automatic power factor correction panel. As such, I have to connect a capacitor to the contactor. To which contactor viz main, delta or star contactor should the capacitor be connected.

  89. Kalpesh

    Respected sir,
    i am having a 15 hp motor which runs with vfd during auto mode and runs by star delta during manual mode, sir the motor runs okay in manual mode but during its auto mode the body gets phased and voltage across the terminals is that of the single phase one so please convey me with the problem and the solution.

  92. Mark

    I have a 440 3 phase 1.5h.p.motor on lathe. On plate, it only states 440. Can this motor be altered to run with a single phase to 240v 3 phase inverter?

  93. Ghulam Hussain

    Dear sir .i have a single phase motor. which takes 15 amp on full load. so i have installed many diffrent contactor with diffrent amp. withins few days contactor is going to out of order. can any one help to to solve this problem ?
    Looking ahead for your kind reply….

  94. Rajaptel Biradar

    Dear Sir,

    I need some helps how can i change direction of rotation of 20 hp motor in star delta by changing leads in motor terminal box

  100. Jafar

    sir
    I like to connect a Crompton greaves 15 HP Starter
    How to connect this.
    Starter identification 2 L3 3 L1
    L2 A1 B1 C1 1
    motor symbol. A1
    C2 A2 this type 6 connection place other 3 cant to identify how to connect 6 wires

  103. suresh

    Sir.. recently i am in utter confussion as my 40hp motor is not pulling the load weight ie a primary jaw crusher.. which are confortably run by 30hp.. but unfortunate my motor could not carry any load although doing quite ok when the load is removed From it so can u kindly suggest any problems and remedies .. also kindly send me the wiring diagram from oil emersed starter to motor.. hoping for ur kind anticipation

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  105. lisha

    i have to design a control panel .It consists of load from booth blower 7.5kw and electrical heater 135kw. what are suitable mccb.mpcb, current transformer ,MFM etc.How to select.

  112. kumaran

    Sir,
    i will connect the 3 hp crompton gear motor (conveyor), with the use of star delta starter or ordinary starter.

  113. Lemau

    Hi, You can use DOL starter.But for the best practice,I suggest you to use Variable Speed Drive.You can control motor speed and energy efficiency

  114. salik

    sir mujhe dol controling and star delta controling ke bare me bataye mujhe tanki bhi smajh me nahi aata
    mai three years se elcectrician post me karyrat hu
    please jald bataye sir

  115. santosh dhadke

    Can u explain me about 7.11 Hp motor how much taken no load current ? But this motor is rewinding motor .

  116. santosh dhadke

    Pls explain me 7.11 Hp 3 phase motor how much taken no load current?
    Also this motor is rewinding motor.

  117. Muwonge Joel

    Hi sir, am very glad by your service. am an electrician working in a factory but am new in the field. i request u to give me lessons on my email, mwngjoel@gmail.com because am facing many challenges. am waiting for your service sir.

  120. Rishikant sharma

    sir
    help me please to know that conection of star delta moter panal
    givr me thesiggesion that how can we make a star delta moter panal

  121. afolayan tunde

    star not changing to delter position, am not sure if timer is the problem

  122. Lemau

    HI,
    Please check your control circuit first…make sure it work properly before you switch on the power cirucit…

  129. EMAD HAMED

    WHAT IS THE MAXIMUM MOTOR POWER TO CONNECT IN (DIRECT ON LINE) METHOD TO STARTING THE 3PHASES INDUCTION MOTORS?

  135. shakoor ahmad

    if the contactor coil voltage is 110 ac & your line voltage is 440or 380 than you must need a step down transformer from 440 v to 110 v for control supply .

  138. ranveer

    star not taking running direct take delta what problem
    before some time both work.
    but this time only take delta.

  139. rathnam chargeman 33 kv

    you never state the motor hp
    1 check you pulley
    2 check you bearing
    3 check you contactor 3pole or 2pole
    4 simple test di connected the pulley and test free load

  140. rathnam chargeman 33 kv

    for star delta starter you must change the main supply RYB TO YBR IT WILL BE OK

  141. Majid.

    Dear sir!
    Please send me the way of how to select proper cable for desired load…

  144. M. Saleem

    Hello,
    I want to know that will the star delta starter procedure operate for duel voltage motors ?such as if motor has 220 to 460/3/60 then either power can be apply on motor or there will be any difference in connections for 220 and 460 volts? regards.

  147. chinmaya biswal

    Hi,
    Iam chinmaya i want to know when connection in motor side in star delta i dont have to know The colour code then how to check in feeder side that connection should be ok or not.
    please Help me .

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