Star delta motor connection

For star delta stater,the motor connection must have 6 cables from control panel and 6 terminals at induction motor ( U1,U2,V1,V2,W1,W3).To wiring the motor connection for star delta starter,the important thing that we must fully understand is about the basic of STAR DELTA MAGIC TRIANGLE.

For detail about star delta stater please read my last post about it. From this triangle diagram,we can determine the correct phase,cable termination for right terminal and the rotation.As we know,the star delta stater is so tricky if we not fully understand the concept and their method. This time i want share my technique when perform wiring task and connected to the star delta stater for induction motor.

Don`t worry,it simple and easy if we understand the basic concepts.I explains detail step by step how to do it :D

 

What is Star Delta connection?

Star delta magic triangle

When we refer to this diagram,We can see correct terminal for the winding for each phase : *CAUTION: Please refer to the name plate of motor to confirm the winding numbering ( U1,U2,V1,V2,W1,W2 ) and the motor connection of winding.

Why it very important??Because each manufacturing have their own style for numbering and winding motor connection.

Star Delta phase and terminals

RED PHASE : U1 and W2 YELLOW PHASE : U2 and V1 BLUE PHASE : V2 and W1 So..from this formula,we must wiring the motor follow the phase color code.

See my example below :-

We can refer the complete wiring for star delta starter diagram below.If you want change their rotation for clock-wise or anti clock-wise,you need change two of phase ( RED or BLUE) at delta contactor.I share the technique how to change rotation in my next post.

If you want motor rotation for clock-wise,the phase colors are RED,YELLOW,BLUE.But if you want anti clock-wise rotation,the phase colors are BLUE,YELLOW,RED.For star delta control wiring diagram,please refer to my post about star delta diagram control

Comments

  1. BHARGAV says:

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

  2. 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.

  3. Venkatesh says:

    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 ??

    • 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

  4. 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

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

      • fayyaz says:

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

      • sreeraj says:

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

  5. Please give the time setting of changeover delay from star to delta. Does it depend on kW or speed or LRC of motor?.

    • 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.

  6. zonaid hasan says:

    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

    • 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.

  7. manoj bhangale says:

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

  8. B.Srinivasa Raju says:

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

  9. Pulak says:

    sir we want the diagram

  10. 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?

  11. IRSHAD AHAMED says:

    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

    • Anil Paul Jacob says:

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

  12. how rating motor connet in star delta

  13. Sadoon says:

    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

  14. Sadoon says:

    Dear Sir,

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

    thank you

  15. Thanks, very helpful

  16. 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

  17. 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

  18. Godswill Onwusoroaka says:

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

  19. Najesh says:

    can we replace contactors with triac… can you give ckt dia on that……

  20. Dancan says:

    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

    • 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….

  21. send me the formula of selecting the conductor size for wiring

  22. please send me the formula to selecting the conductor size to wiring

  23. 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.

  24. I like to Automation from you

  25. Lim KB says:

    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?

  26. jackie says:

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

  27. jackie says:

    ^ for reversing direction of motor

  28. the phase shifting from main to delta contactor should take place,while changing star to delta.

    if anybody can clear this ,please reply

  29. Hello you have mentioned the wrong numbering, kindly correct the same.

  30. fayyaz says:

    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.

  31. fayyaz says:

    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.

  32. dinesh kumar says:

    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.

  33. hello sir,
    i want difference between relay and contactor?

    • 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.

  34. 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

  35. 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

  36. Anil Paul Jacob says:

    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.

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

  37. alexander says:

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

  38. Anil, thank you so much for your information,Iam glad

  39. AK Majumdar says:

    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.

    • 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

  40. Siva balan says:

    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

    • 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

  41. Habeeb says:

    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 .

    • 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.

  42. mahesh deshmukh says:

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

  43. sumith mohan says:

    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.

  44. 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 ????

  45. Mr.Gururaj Deshpande. says:

    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?

  46. simret says:

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

  47. rahui singh thakur says:

    how tp find the terminals pf motor which one is u1 u2., v1 v2 , w1 w2

  48. how to find the terminals of motor which one is u1 u2 , v1 v2 , w1 w2

  49. Aditya Sarma says:

    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

  50. Aditya Sarma says:

    helo sir how can i calculate the capacitor required for a submersible motor for installing it in a control panel ie. i need to install a capacitor for a 110 HP motor how can i choose the right one

  51. ABDUL HAFEEZ AKHTAR says:

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

  52. 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.

  53. yikunoamlake haile says:

    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.

  54. khukon says:

    Haw do concreter push button convection

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