Three Phase Delta-Wye Xfmer Power Calculations

Thread Starter


Joined Sep 13, 2010
Evening gents,

I was wondering if you guys could quickly check over my work for the following practice problem.

See figure attached for problem statement, and the attached pdf for my worked solution.

If there is any confusion regarding my worked solution please ask me for further clarification in this thread and I will explain in greater detail what I have done.

Thanks again!



Joined Mar 6, 2009
Generally I would say your solution looks OK.

One exception would be the conversion of the p.u. transformer impedance.
On page 2 ....

You state the transformer secondary side impedance value as

Zeq2=2.42+j5.808 Ω

You are presumably transforming everything to a Wye connected per phase equivalent.

Since the transformer secondary is delta connected, I assume one would need to convert the Zeq2 value to an equivalent Wye form where Zwye=Zdelta/3. This would be in the same context as converting the delta connected motor load to an equivalent Wye impedance.

Other than that I see no problems.