3phase induction motor. Effect of Delta connection & Star connection

Discussion in 'Homework Help' started by Jess_88, Oct 29, 2011.

  1. Jess_88

    Thread Starter Member

    Apr 29, 2011
    Hey guys :)

    I was just wondering is someone could tell me how a delta or Star connection changes how an equivalent circuit would be analysed.

    Is it as simple as just different input voltage and current?
    Star: VL = √3Vphase, IL = Ip
    Delta: VL = Vp, IL = √3Ip
    If the motor is rated at, say 230V, with a delta connection, dose this just mean Vin (or V1) = Vp = 230V?

    My main worry is just that, I think I remember my tutor say "we will just assume its star connection. Makes things easier" for a question, not specifying its connection. Dose this make any sense?

    Thanks guys :)
  2. Jess_88

    Thread Starter Member

    Apr 29, 2011
    so... i guess this is a dumb question then :(
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
    Not dumb, but I don't know very many people who have the answer off the top of their head. You need to get the book out and read it. I know the difference between delta and star connect configuration, but I never memorized the equations.

    I think the reason star connect is easier to analyze is because the center of the star can be assumed to be virtual ground.
    Jess_88 likes this.
  4. Jess_88

    Thread Starter Member

    Apr 29, 2011
    ah ok, thanks :)
  5. amilton542

    Active Member

    Nov 13, 2010
    The star configuration will limit the inrush current during the initial start-cycle where it will be switched to delta when up to speed. A bank of induction motors continuously being driven up to speed in delta can be expensive for the bill-payer.

    If you "plug-in" values in the star-delta relationships and make a comparison you will see the differences.