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

Thread Starter


Joined 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 :)


Joined 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.


Joined 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.