Q 12-9 Wildi

[rg1]

Is question 12-9 on page 261 of Wildi has wrong answer wrt angle of line voltage V12

 

[Omer]

I couldn't locate this in my copy. Can you share?

 

[rg1]

I couldn't locate this in my copy. Can you share?

Answer to E12 is 347 leading E23 by 150 degrees.

E31is 347 lagging E12 by 60 degrees. I have similar issues in questions 12-13, 12-14 and 12-15. Once we are done with this we will discuss others.

 

[Omer]

it is very difficult for me to visualize the new reverse connection :blink: .

anyway, calculating based on simply reverse the polarity of secondary P, I got this:

my reference is E (AB)

E12=347@120

E23=600@-90

E31=347@60

 

[rg1]

it is very difficult for me to visualize the new reverse connection :blink: .

anyway, calculating based on simply reverse the polarity of secondary P, I got this:

my reference is E (AB)

E12=347@120

E23=600@-90

E31=347@60

Thanks a lot. I am in agreement with you. It seems I have some wrong solution for it.

Anyways. Do you have another questions with you- 12-13; 12-14; 12-15. They are all one question based on Delta connected auto transformer ( 3 single phase xmers). 

 

[rg1]

Thanks a lot. I am in agreement with you. It seems I have some wrong solution for it.

Anyways. Do you have another questions with you- 12-13; 12-14; 12-15. They are all one question based on Delta connected auto transformer ( 3 single phase xmers). 

I have put Q12-13, 12-14 and 12-15 of Wildi into one. I solved but the answers did not match. Please provide the answers with angles; taking Vab as reference for better appreciation. 

 

[rg1]

You can interchange the positions of H1 with H2 and X1 with X2 if you feel like. That should not make a difference in the answer.

 

[Omer]

@rg1

it looks complicated.

for the single phase transformer:

I primary= 15000/480=31

I sec= 15000/120=125

for the new configuration:

I x max= 125+31=156@0

I a max= 31@0 +125@120= 112@106

Vxy= 120+480@-120= 432@-106

there are high chances I am wrong..

 

[rg1]

The magnitudes are right, that is for sure, angles I am not yet sure. But I am in agreement with you for both. In the given solutions even Vxy is given 465 and Ia as  121. I am sure that must be wrong. 

 

[rg1]

The magnitudes are right, that is for sure, angles I am not yet sure. But I am in agreement with you for both. In the given solutions even Vxy is given 465 and Ia as  121. I am sure that must be wrong. 

I think we are right for angles too.

 

[GaryD]

You guys are very skilled with your thoughts and your overall problem solving abilities.  I hope one day I can attain your skill level.  It is a tough process picking this stuff up though!  I am finally done reading through transformers and am starting three phase induction machines.  I wish everyone the best of luck.

 

[rg1]

You guys are very skilled with your thoughts and your overall problem solving abilities.  I hope one day I can attain your skill level.  It is a tough process picking this stuff up though!  I am finally done reading through transformers and am starting three phase induction machines.  I wish everyone the best of luck.

Thanks @GaryD . Practice makes it. I am sure you will do it. My best wishes. I am making my efforts to test the waters. I really do not know how the real exam, will be. No, one can claim to be a master of this large subject. If I can be of any help, in your process of learning, I will consider myself fortunate.