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Home » AC Fundamentals » Comparison between Star and Delta Connections

Comparison between Star and Delta Connections

Main Different between Star and Delta Connections

Comparison between Star

Comparison between Star and Delta Connections
Comparison between Star and Delta Connections

(Y) and Delta (Δ) Connections

Star (Y) Connection

Delta (Δ) Connection

In STAR connection, the starting or finishing ends (Similar ends) of three coils are connected together to form the neutral point. A common wire is taken out from the neutral point which is called Neutral. In DELTA connection, the opposite ends of three coils are connected together. In other words, the end of each coil is connected with the start of another coil, and three wires are taken out from the coil joints
There is a Neutral or Star Point No Neutral Point in Delta Connection
Three phase four wire system is derived from Star Connections (3-Phase, 4 Wires System) We may Also derived 3 Phase 3 Wire System from Star Connection
Three phase three wire system is derived from Delta Connections (3-Phase, 3 Wires System)
Line Current is Equal to Phase Current. i.e.

Line Current = Phase Current

IL = IPH

Line Voltage is Equal to Phase Voltage. i.e.

Line Voltage = Phase Voltage

VL = VPH

Line Voltage is √3 times of Phase Voltage. i.e.

VL = √3 VPH

Line Current is √3 times of Phase Current. i.e.

IL = √3 IPH

The Total Power of three phases could be found by

P = √3 x VL x IL x CosФ …. Or

P = 3 x VPH x IPH x CosФ

The Total Power of three phases could be found by

P = √3 x VL x IL x CosФ … or

P = 3 x VPH x IPH x CosФ

The speeds of Star connected motors are slow as they receive 1/√3 voltage. The speeds of Delta connected motors are high because each phase gets the total of line voltage
In Star Connection, the phase voltage is low as 1/√3 of the line voltage, so, it needs low number of turns, hence, saving in copper. In Delta connection, The phase voltage is equal to the line voltage, hence, it needs more number of turns.
Low insulation required as phase voltage is low Heavy insulation required as Phase voltage = Line Voltage.
In Power Transmission, Star Connection system is general and typical to be used. In Power Distribution and industries, Delta Connection is general and typical to be used.

Click image to enlarge

difference between star and delta configuration
Comparison between Star and Delta Connections

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51 comments

  1. Comparison bw star and delta made me understand why star delta starter is used for 3 phase ac motors.

    • star is used for below 5 hp motors and delta is used for above 5 hp ….. when motor gets starts ,it starts with star after that it changes to delta by using timer because, when the motor stars motor gets highs amps at first star works after that delta works

    • Its bcoz to increase the speed of motor while starting gradually.. since the phase voltage is 1/√3 of line voltage the starting speed of the motor will get reduced after a specific time it have to get changed to delta inorder to deliver more power

  2. Please correct – Delta Connections – 3rd point –

    It should be
    “Three phase three wire system is derived from Delta Connections”

    not Star Connections.

    In the image also.

    Thank you.

  3. Why Star connection and Delta connection is necessary for Motors ?

  4. THANKS FOR GUIDE

  5. i need the delta and star

  6. Very good website

  7. can any one tell me in star delta mode,, in which state motor take high or more current…. in Star or Delta

  8. Thanks for the guidance…

  9. Thanks SAR very good sejestion

  10. I WANT TO BE THE PART OF THIS GOOD KNOWLEDGE SHARING WEB SITE.

  11. how do I generate neutral from delta connection

  12. Thanku for guidance star and delta cannection explain

  13. What is diffrence between neutral and earthing. Please give me ans

  14. Thanks for the guidance.

  15. Hello all;
    i need the Circuit diagram of how to turn on automatically a 3 phase Generator?

  16. Thanks for the guidance.

  17. HOW WILL YOU TEST THE RESISTANCE OF A STAR CONNECTED MOTOR

  18. Whether u connected in star or delta….speed doesn’t varies know…only torque differs….change the answers in difference column

  19. Good day!
    In our industrial electrical facilities has some motor like big cooling fan has delta connection (50HP) If we will change the motor winding connection from delta to star, is any benefit from energy Saving point of view.

    your feedback is highly appreciated.

  20. Sir ye star me neutral kyu hota h,delta kyu nhi hota h?

  21. greetings
    i think the star connection is used for the distribution (to provide the single phase voltage ) , and the delta is used for transmission (higher voltage , more insulation is required but we transmit by OHTL (air is our insulator ) .
    its reversed in the article i think ..or may be there is something i am missing .

  22. Dear admin
    Please check the last point, is this true that delta used for distribution and star used for transmission ?

  23. Which type of connection os better for 25hp Motor if it is connected to power pack….. we connected in star is it ok

    • u have to operate motor in star – delta connection both, initialy 25 hp motor required more force to move its shaft but as soon as it attain some speed it an be transferred to delta. we use this type of combination above 5 h.p. motors.

  24. I want to use motor for running compressor motor details 440v,60hz, and 130Amps normal working current ,power 80kw load.
    Starter is DOL.
    Please give advise how should I connect motor terminal in star or delta
    Thanks

  25. Dear sir,
    can u prove why star connected motor takes low current than delta connected motor.

  26. Hi! Does the imbalance between the phases can be caused by type of connection? Ex. There’s phase? 2 pole induction motor and phases have the following values of current: A=130A, B = 125A, C=120A. Why they’re not the same?

  27. Between star and delta connection which of them takes a high voltage either in primary or secondary coil

  28. Why delta connection is require for motor??????
    In home….what kind of connection we use????

  29. best comparison between delta and star connection

  30. SAUMITRA PRAMANIK

    There is no change in speed for both star and delta connection for induction motor Speed N = 120F/P i.e. Speed depends upon only supply frequency and No of pole in motor speed can not change due to voltage variation for Ac induction motor – star delta connection used for Ac induction motor.

  31. please sir according to your circuit diagram on connection of motor in star delta why is the star terminal in series and the delta in parallel

  32. One 63.5 KVA genset 3-Phase is connected to load( machine). Starting in Star connection is OK but during the load transfer to delta connection , motor (machine) trips off. What can be the possible reasons?

  33. If in place of star connection,we give delta connection.What will happen to the Motor?

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