Need help w/ a question...

Serendipity

Any help would be greatly appreciated - A 3-phase, 3-W transformer has the following ratings: 13.8kV(delta)/345kV(Y)/4.16kV(delta); 300/300/30MVA. A short circuit test is performed, providing the following data:

Primary -
1. Measured
2. Open Circuit
3. Short Circuit

Secondary -
1. Short Circuit
2. Measured
3. Open Circuit

Tertiary -
1. Open Circuit
2. Short Circuit
3. Measured

The values for V_sc / sqrt(3) in kV are the following:
1. 2.4268
2. 14.181
3. 0.07305

The values for I_sc (in Amperes) are:
1. 12551
2. 50.2
3. 4164

And the values for P_sc/3 (in kW) are:
1. 66.67
2. 48.15
3. 55.56

The question asks to calculate the positive-sequence equivalent circuit values in per-unit, referred to S_3(phi)base = 100MVA, and the transformer voltage ratings. (a) Find the base values for all three windings. (b) Convert tthe given test data into per-unit. (c) Calculate all three short circuit impedances from the data in above.

Thanks in advance!

FTGV

The answer is ............40


And the purpose of this exercise is?

Serendipity

FTGV wrote: »

And the purpose of this exercise is?

I'm studying for my Midterm and don't understand this question.

mdaudioguy

FTGV wrote: »

The answer is ............40

Wrong! It's 42.

mrbigbluelight

Serendipity wrote: »

I'm studying for my Midterm and don't understand this question.

That's okay, I'm NOT studying for your Midterm and I don't understand the question, either.

You could always convert to an equivalent Thevenin circuit but being as that doesn't have a dang thing to do with the question, that probably wouldn't help much.

I admit to not being helpful. 44.

Serendipity

Apparently you have to do something with the given values, that I'm not understanding how to do so, but no equation in the text makes use of all three at the same time. And looking back at a previous course (E&M Physics and Transmission Lines), I can't find a formula that will work with the above.

searay40dad

thank you for another reminder of how much i've forgotten in 25 years i'd have to go back for another 4 years to remember that stuff. sorry, no help here as v=ir is about all i got now.
good luck with the midterm

cnh

I can't answer your question but I probably have some Chinese students who can provide the correct answer in no time? When's the midterm...?

And is that 42 above serious or is it just a quote from the Hitchhiker's Guide to the Galaxy? lol

cnh

Serendipity

cnh wrote: »

I can't answer your question but I probably have some Chinese students who can provide the correct answer in no time? When's the midterm...?

cnh

Monday, so I still have tonight and tomorrow night to study.

Thanks!

lightman1

Don't know. But I can wire that sumbitch up to specs!

cnh

hmmmmm! I'll ask but that's a tight schedule...we are 12 hours ahead so this may or may not work....since I have to wait till Monday morning my time which is Sunday night your time if you're on the East Coast?

Keep studying and I'll see if I can get back to you and if one of my guys works in this area?

Good Luck...


cnh

Serendipity

Monday in China would equal Sunday night, at least here on the East Coast.

I really appreciate your help!

mdaudioguy

cnh wrote: »

And is that 42 above serious or is it just a quote from the Hitchhiker's Guide to the Galaxy? lol

cnh

Yes.

Serendipity

Just finished the test. Holy cow there was so much material! My hand is hurting! I did most of the questions but barely had enough time to finish. And to make matters worse, I have another exam tomorrow.

A note to college students: Physics of Power Systems is MUCH harder than E&M Physics and Transmission Lines!!