# Looking for help in "Per Unit" calculations

Discussion in 'General Electronics Chat' started by Ohshift, Mar 26, 2011.

1. ### Ohshift Thread Starter New Member

Nov 12, 2010
2
0
I have an internship interview Monday morning where I am expected to understand per unit applications in transformers. It couldn't be worse timing, I talked to my EM devices teacher and we are scheduled to start this topic next week.

I have read through a few power systems books, but they seem to explain the concept of per unit very well, but examples are lacking.

Are there any electrical engineers here that can point me to examples on how to apply this technique to solve for voltages, currents, impedances, in each segment of a series connected transformer circuit? (even a name of a great book is greatly appreciated)

In particular I am looking for multiple (3+) transformers in series to practice.

Thanks

2. ### pilko Senior Member

Dec 8, 2008
213
20
From my recollection in university (way,way back) we used per unit values to express proportions instead of using percentage values.
For example 0.2pu = 20% ; 0.65pu = 65% etc.

pilko

3. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
784
There should be numerous worked examples on the web. Not necessarily with your particular example - but you could extend the ideas to your case.

Here's one link for example ...

Edit: posted link didn't work - Look for ~baldick/classes/369/​Lecture_​8.ppt university of Texas EE (not ECE) 369 "Power Systems Analysis"

& this as a brief background summary

Last edited: Mar 26, 2011
4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
784
You can also download (free) the full version of the title

"Schaum_Electric_Power_Systems.pdf"

It has examples of the per unit system method in chapter 2.

5. ### Ohshift Thread Starter New Member

Nov 12, 2010
2
0
Thank you so much, that PPT is exactly what I need.

6. ### Will_Linn New Member

Sep 8, 2011
1
0
Hey,

I see from the thread date that i maybe missed the conversation by a year or so.

Has anyone any worked examples to the Schaums text.

After viewing this post i went and downloaded the book. I'm starting a self taught masters in a few weeks and been trying to brush up on fault calculations only i am totally lost with some of the problems.

can anyone here offer any help?