Star delta motor connection
For star delta stater,the motor must have 6 cables from control panel and 6 terminals at induction motor ( U1,U2,V1,V2,W1,W3).To wiring a connection for star delta motor,the important things we must fully understand 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.
This stater is so tricky if we not fully understand the concept and their method. This time i want share my technique when i wiring and connected 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
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 connection of winding. Why it very important??Because each manufacturing have their own style for numbering and winding connection.
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 see the fully wiring for star delta from below diagram.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.
If you want 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 
DER SIR
PLS REPLY ME FORMULA OF SELECT CONTACTOR & OVERLOAD REALY FOR STAR DELTA AND DOL STARTING.
THANK YOU
For overload relay sizing,please read my last post : http://www.electricneutron.com/motor-control/overload-relay-setting-and-calculation/
For magnetic contactor sizing,the basic formula is : full load ampere x 1.25.
please read my post for more detail : http://www.electricneutron.com/motor-control/magnetic-contactor/
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
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.
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
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.
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.
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.
Hi,
Please give me control circuit dia. with explanation of star-dalta starter.
Dear manoj bhangale,
please refer to my last post about control circuit wiring diagram completed with star delta explanation.
http://www.electricneutron.com/motor-control/electro-mechanical-star-delta-starter/
Thanks
I want star delta connection from starter in side terminal to motor terminal box with colour code
I already explain in my post..you just follow the wiring diagram for power circuit with color code..
thanks
sir we want the diagram
Dear pulak,
Please refer to my last post for star delta starter diagram control circuit : http://www.electricneutron.com/motor-control/electro-mechanical-star-delta-starter/
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?
please check your magnetic contactor ampere rated and types.Please refer to my last post : http://www.electricneutron.com/motor-control/sizing-for-magnetic-contactor/ and also http://www.electricneutron.com/motor-control/star-delta-starter/
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
how rating motor connet in star delta
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
Thanks for the reply :D
Dear Sir,
can we have the same explanation on Auto-trans starter used in motor.
thank you
Thanks, very helpful
ur welcome..thanks visit my blog
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
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
i connected a 110kw of motor to star-delta but the speed is seem to be slow, what is the problem
can we replace contactors with triac… can you give ckt dia on that……
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….
send me the formula of selecting the conductor size for wiring
please send me the formula to selecting the conductor size to wiring