Please help! Confusion with 30 degree phase angle shift between delta wye in a transformer

[poosri]

Hi All,

This phase shift seems to be killing me.

Based on Wildi,

if wye connected, V L-N = (V L-L/sqrt 3) at angle -30 degree

if delta connected I phase = (I line/sqrt 3) at angle -30 degree

But in the attached problems, eg. E-25, at the end, Ia seems to be calculated at -30 degree. I think Ia must be 173 at angle 10 degrees (+30-20)? same follows in problem E-26 Ia must be 300 at -20 degrees?

Thanks for your help/time!

Transformers.pdf

 

[seandapaul24]

This can be confusing. Even some books get it wrong.

The phase shift is between high side and low side. The high side can be either:

A) Delta for Delta-Wye transformer or

B) Wye for a Wye-Delta transformer.

In both cases(A or B) the high side leads the low side by 30 degrees.

 

[Ken PE 3.1]

Check out the complex imaginary video on this topic. They cover it fairly well.