# 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
174
1
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
174
1
so... i guess this is a dumb question then

3. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
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
174
1
ah ok, thanks

5. ### amilton542 Active Member

Nov 13, 2010
494
64
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.