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

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poosri

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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

 

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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.

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

 
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