# Turns ratio confusion



## rg1 (Aug 13, 2017)

I never had an issue with turns ratio of a Xmer but while preparing for PE. I have been conventionally considering it same as voltage (Line/Phase) ratio whether in star star; delta delta or star delta  What should one answer for turns ratio when you face such a question in PE in star delta. Should it be Voltage Ratio (Transformation ratio) or physical turns ratio. There was a question in PPI-1.


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## TNPE (Aug 14, 2017)

The voltage ratio may be given in line quantities, but the turns ratio of the XFMR is always with regards to phase (e.g. phase for delta is LL and phase for wye is LN).


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## rg1 (Aug 14, 2017)

TNPE said:


> The voltage ratio may be given in line quantities, but the turns ratio of the XFMR is always with regards to phase (e.g. phase for delta is LL and phase for wye is LN).


Thanks. Is it legislated somewhere, except in practice tests solutions?


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## TNPE (Aug 14, 2017)

No problem.

The confusion with most of these scenarios is attributed directly to language.  However, if you think of it intuitively, it makes perfect sense.  As I've said before, the PE exam will ask you EXACTLY what they're looking for.  There should be no confusion if you're well-versed (and from what I've seen, you are, and you should have no trouble).  As far as it being legislated, I don't know that I would define it that way.  Just know that a voltage ratio and XFMR winding ratio can be different, depending on winding configuration.  Just remember, you will always be relating the phase voltages to one another when working with winding ratios (Always, Always, Always).


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## rg1 (Aug 14, 2017)

TNPE said:


> No problem.
> 
> The confusion with most of these scenarios is attributed directly to language.  However, if you think of it intuitively, it makes perfect sense.  As I've said before, the PE exam will ask you EXACTLY what they're looking for.  There should be no confusion if you're well-versed (and from what I've seen, you are, and you should have no trouble).  As far as it being legislated, I don't know that I would define it that way.  Just know that a voltage ratio and XFMR winding ratio can be different, depending on winding configuration.  Just remember, you will always be relating the phase voltages to one another when working with winding ratios (Always, Always, Always).


Thanks a ton. The student in me remains agitated till I discuss this kind of  stuff with some one. When I saw the question, I knew what he wants to ask and did it right, but the student ?  You have been useful in fixing these loose ends, tit bits.


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## rg1 (Aug 24, 2017)

Can someone help me in understanding the turns ratios  shown in the answer. Are they okay? Thanks in advance.


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## Omer (Aug 25, 2017)

As I understand, those are different transformers with different turn ratio for each specific connection but all can handle the requirements.

i think turn ratios are ok. @rg1


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## rg1 (Aug 25, 2017)

Omer said:


> As I understand, those are different transformers with different turn ratio for each specific connection but all can handle the requirements.
> 
> i think turn ratios are ok. @rg1


Omer thanks for your response.  I did not get it. Can you show the calculations for say, star star connection, the first  in the  solution. I am  feeling agitated, by not getting it.


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## Omer (Aug 25, 2017)

Sorry  @rg1, I think the calculation is wrong. It is 3.13:1 for the first one. It should be straight primary phase voltage/ secondary.

i don't know why most of the problems showing on the board nowadays having mistakes.?


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## rg1 (Aug 25, 2017)

Omer said:


> Sorry  @rg1, I think the calculation is wrong. It is 3.13:1 for the first one. It should be straight primary phase voltage/ secondary.
> 
> i don't know why most of the problems showing on the board nowadays having mistakes.?


Yes, that is what I also concluded. These questions are from Chapman. I supposed, it was a good publication. May be it is old edition. The answer to your second statement is- it implies the guys are getting all questions which do not have mistakes in it.  The only questions coming for discussions are those, which have mistakes in them.That implies more percentage of guys passing this time. A signal for celebrations.


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## GaryD (Sep 1, 2017)

rg1 said:


> Yes, that is what I also concluded. These questions are from Chapman. I supposed, it was a good publication. May be it is old edition. The answer to your second statement is- it implies the guys are getting all questions which do not have mistakes in it.  The only questions coming for discussions are those, which have mistakes in them.That implies more percentage of guys passing this time. A signal for celebrations.


Hey @rg1 do you think the book by Chapman is essential?  I'm just wondering if it will be worth my while.


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## TNPE (Sep 2, 2017)

GaryD said:


> Hey @rg1 do you think the book by Chapman is essential?  I'm just wondering if it will be worth my while.


If you're talking about Stephen Chapman, then yes, it is an essential.  I used it almost exclusively when I took the PE (also used Graffeo, NEC and NESC, where practical).  I also used a few other college texts for specific problems, but used Chapman and Graffeo for at least 75-80% of the exam.


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## GaryD (Sep 2, 2017)

TNPE said:


> If you're talking about Stephen Chapman, then yes, it is an essential.  I used it almost exclusively when I took the PE (also used Graffeo, NEC and NESC, where practical).  I also used a few other college texts for specific problems, but used Chapman and Graffeo for at least 75-80% of the exam.


Thanks for the feedback.  I just ordered the paperback through amazon for 40ish dollars.  Hopefully will arrive within 1-2 weeks!


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## Stephen2awesome (Sep 2, 2017)

Chapman or Wildi?


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## knight1fox3 (Sep 3, 2017)

Both.


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## rg1 (Sep 3, 2017)

GaryD said:


> Hey @rg1 do you think the book by Chapman is essential?  I'm just wondering if it will be worth my while.


As far as comments on references are concerned I would put a rider first- I am old; new at US, so discount that before you take anything I advise. Chapman is a good book. I do not have an experience of the PE exam itself, but I personally find Wildi better. I have got pdf copies of both, i have printed wildi for the exam. I, just at times, go through Chapman on my laptop. Few of the topics like magnetic flux stuff, auto Xmer are better explained in Chapman than it is done in wildi. Over all Machines are better explained in wildi. If you have both as I see in later posts, it is for good, you can have best of two worlds.  The forum is very rich in info and you can choose best suited to you.


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## GaryD (Sep 4, 2017)

rg1 said:


> As far as comments on references are concerned I would put a rider first- I am old; new at US, so discount that before you take anything I advise. Chapman is a good book. I do not have an experience of the PE exam itself, but I personally find Wildi better. I have got pdf copies of both, i have printed wildi for the exam. I, just at times, go through Chapman on my laptop. Few of the topics like magnetic flux stuff, auto Xmer are better explained in Chapman than it is done in wildi. Over all Machines are better explained in wildi. If you have both as I see in later posts, it is for good, you can have best of two worlds.  The forum is very rich in info and you can choose best suited to you.


You can't be that old - I myself think I am older than the average user of these forums (32 years).  You have the mindset of one who is hungry and trying to expand their capacity.  Thank you for the input - I do have the PDFs as well but I have decided to buy the international paperback copy of Wildi.  I recently ordered the Chapman paperback as well based off the other gentleman's feedback.  Where you from and where do you currently live?  Maryland here.


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## TNPE (Sep 4, 2017)

GaryD said:


> You can't be that old - I myself think I am older than the average user of these forums (32 years).  You have the mindset of one who is hungry and trying to expand their capacity.  Thank you for the input - I do have the PDFs as well but I have decided to buy the international paperback copy of Wildi.  I recently ordered the Chapman paperback as well based off the other gentleman's feedback.  Where you from and where do you currently live?  Maryland here.


I, too, am 32.  Took the exam at 31, though.  I don't necessarily agree with rg1 with regards to Chapman.  I think you can almost pass the test exclusively with his book, Graffeo, NEC and NESC.  Now, I wouldn't show up with only those materials, but it is easily passable with them alone.  I do not own a copy of Wildi, but I have made a cursory scan of it.  IMHO, it is more of an "academic" book, but Chapman is better suited for this type of scenario (Chapman was actually a college text of mine).  This exam is not about "academics" per se, rather it is more about fundamentals and knowing how to work problems that take an average of 6 minutes to complete.  The student in me loves academia, but the PE in me loves preparing to pass the test the first time around.  By no means, I'm not telling you not to use Wildi, but don't get bogged down in the academics.  Learn the approaches and techniques and move on.


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## rg1 (Sep 4, 2017)

TNPE said:


> I, too, am 32.  Took the exam at 31, though.  I don't necessarily agree with rg1 with regards to Chapman.  I think you can almost pass the test exclusively with his book, Graffeo, NEC and NESC.  Now, I wouldn't show up with only those materials, but it is easily passable with them alone.  I do not own a copy of Wildi, but I have made a cursory scan of it.  IMHO, it is more of an "academic" book, but Chapman is better suited for this type of scenario (Chapman was actually a college text of mine).  This exam is not about "academics" per se, rather it is more about fundamentals and knowing how to work problems that take an average of 6 minutes to complete.  The student in me loves academia, but the PE in me loves preparing to pass the test the first time around.  By no means, I'm not telling you not to use Wildi, but don't get bogged down in the academics.  Learn the approaches and techniques and move on.


Hmmmm,  Will you suggest to attempt. questions at the end of chapters of Chapman.


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## TNPE (Sep 4, 2017)

rg1 said:


> Hmmmm,  Will you suggest to attempt. questions at the end of chapters of Chapman.


I have worked a lot of them at some point in my past, but I was speaking to presentation and overall layout of the book.  I takes a fundamental, foundational approach.


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## rg1 (Sep 4, 2017)

rg1 said:


> Hmmmm,  Will you suggest to attempt. questions at the end of chapters of Chapman.






TNPE said:


> I have worked a lot of them at some point in my past, but I was speaking to presentation and overall layout of the book.  I takes a fundamental, foundational approach.


My problem is, after reading a chapter I would like to test myself. There, I find Wildi has so many questions at the end of the chapters. The problem with PE exam is, there are not many actual matching sample tests (matching with real test) available in the market because of the confidentiality clause. I get restless, when I am not able to test myself where I stand  as far as preparation is concerned and that results into more studying. All is for good. I think there is need of fortune teller in this field- a good profession lol.


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## TNPE (Sep 4, 2017)

Hard to have a defined system if everyone knew the problems, therefore, either diminishing the value of being a PE or being impossible to pass.  Best I can give you is this, the test is almost identical in difficulty and style to the published practice exam.


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## rg1 (Sep 4, 2017)

TNPE said:


> Hard to have a defined system if everyone knew the problems, therefore, either diminishing the value of being a PE or being impossible to pass.  Best I can give you is this, the test is almost identical in difficulty and style to the published practice exam.


Thanks a lot. Let us see, count down has begun!!! I do not  think last two weeks can be used for studies, as those will be the times to plan for the exam, cheat sheet etc.


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## TNPE (Sep 5, 2017)

I used the last two weeks to tidy up any loose ends on topics I was weaker on.  I didn't use a cheat sheet, rather I learned my materials while studying (developed comfortability) and let that be my "cheat sheet."  

There's not a template that is all-inclusive such that any person could follow it and pass.  If there were, I'd gladly give it to you.  You know your strengths and weaknesses.  Bolster your strengths and mitigate your weaknesses.  

I cant stress enough how important it is to know your materials.  Really, just as important if not more so than being a "student" of the subject matter.  There are dozens (maybe hundreds) on this very forum who may even admit that.  Some fail the exam due to underestimating what's required to pass and they sleepwalk during preparation, others miss the mark by not being proficient with their resources. 

Good luck!  If you have any other questions during the countdown, please post them.


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## rg1 (Oct 9, 2017)

Now, what are the figures 1:4 and 2:1 in the attached figure, here? Are they Turns Ratios (Phase Voltage Ratio) or Voltage Transformation Ratio of Xmers. The PPI guys are taking it as turns Ratio? In the particular question I got it right even by Voltage transformation Ratio because it was from Star to Delta and then again Delta to Star  transformation but PPI is doing it with turns ratios. In the Exam I do not know what should we take. It will make a difference if it is a single Transformation or even multiple transformations of similar type?


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## Stephen2awesome (Oct 10, 2017)

Turns ratio here. If only given voltages, then use the voltage ratios. When using voltage ratio is this senerio, need to make sure you do the ratio of either Vphase or VLL  on each side.


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## rg1 (Oct 12, 2017)

Stephen2awesome said:


> Turns ratio here. If only given voltages, then use the voltage ratios. When using voltage ratio is this senerio, need to make sure you do the ratio of either Vphase or VLL  on each side.


Thanks


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