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Difference between Star and Delta Connections – Comparison Of Y/Δ

Comparison between Star and Delta Connections

We mostly use the terms star and delta in electrical systems while discussing three phase AC circuits and electric motors. Below is a given table which compares both Star and delta connections showing the exact difference between Star (Y) and Delta (Δ) Connections.

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


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

Line Voltage = Phase Voltage


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 a 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 lowHeavy 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.

The same table showing differences between star and delta configurations can be seen below if you face any dificulty while readng the text.

Click image to enlarge

Main Difference between Star and Delta Connections
Main Difference between Star and Delta Connections

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    1. 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

    2. 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

  1. 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.

    1. star connection is required at the starting o motor because a motors takes 5-10 times more current at starting and if delta current is given it may start immediately but this may reduce the life of motor

      1. Mr Khan, Pls we are talking about star ? and delta in general here not the process of star – delta connection to start a heavy motor.
        Thank u

    1. Please provide more information… For which purpose, do you want to do that? You mean, You want a single phase supply with neutral wire from three phase (Delta) Generator or what?

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

  3. 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.

  4. 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 .

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

    1. 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.

  6. 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

  7. 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?

  8. 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.

  9. 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

  10. 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?

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