Star delta motor connection Electric Motor
What is Star Delta 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 aconnection for star delta motor motor,,the important things we must fully understand the basic of STAR DELTAMAGIC DELTA MAGIC TRIANGLE. For detail about star delta stater please read my last post about ab out it. From this triangle diagram,we can determine the correct phase phase,,cable termination for right terminal and the rotation. This stater is so tricky if we not fully understand the concept and their method method.. This time i want share my technique when i wiring and connected the star delta stater for induction motor. 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 diag ram,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 terminal RED PHASE : U1 and W2 W 2 YELLOW PHASE : U2 and V1 BLUE PHASE : V2 and W1 So..from this formula 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 thei r rotation for clock-wise or anti clock-wise,you need change two of phase ( RED or BLUE) at delta delt acontactor 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
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Edit))PERMALINK BHARGAV19 May 2011 at 7:21 PM(Edit DER SIR PLS REPLY ME FORMULA OF SELECT CONTACTOR & OVERLOAD REALY FOR STAR DELTA AND DOL STARTING. THANK YOU REPLY
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Edit))PERMALINK lemau20 May 2011 at 6:53 AM(Edit For overload relay sizing,please read my last post : http://www.electricneutron.com/motorcontrol/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/magneticcontactor/ REPLY
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Edit))PERMALINK Gaurav Khanduja9 June 2011 at 2:21 PM(Edit
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 Co s $ (.9)] * .58 REPLY
2. Edit))PERMALINK Sinnadurai Sripadmanaban 5 June 2011 at 7:36 AM(Edit 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. REPLY
3. Edit))PERMALINK Venkatesh11 June 2011 at 4:44 PM(Edit 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 ?? REPLY
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Edit))PERMALINK lemau11 June 2011 at 10:27 PM(Edit If you want run the motor m otor using star delta starter,u must take off all cooper bar at terminal of electric motor.so no connection of star or delta. del ta. MAKE SURE : The motor design is DELTA connection only for star delta starter.if you used motor design STAR connection,your winding will burn bu rn out :D REPLY
4. Edit))PERMALINK mukul25 June 2011 at 11:58 AM(Edit
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 REPLY
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Edit))PERMALINK lemau25 June 2011 at 2:50 PM(Edit mukul,please check your power supply wiring for motor terminal.make sure ur 3 phase wiring from delta contactor to motor is correct. REPLY
Edit))PERMALINK fayyaz3 June 2012 at 5:44 PM(Edit see reason to stop motor in revers direction in delta connection is the one winding is getting connected in same phase. REPLY
5. Edit))PERMALINK Sinnadurai Sripadmanaban 30 June 2011 at 11:46 AM(Edit Please give the time setting of changeover delay from star to delta. Does it depend on kW or speed or LRC of motor?. REPLY
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Edit))PERMALINK lemau30 June 2011 at 11:06 PM(Edit 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. REPLY
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 REPLY
First, you must know the Full Load L oad 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 mo tor, 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 ca rries 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.
