# Power PE Reference Handbook Errors



## DilutedAr18_PE (Sep 13, 2020)

*Edit: I see this was already discussed. No idea why they would define Vline as Vmax. I don’t know of any other cases where you would use Vline as the maximum value. It just makes no sense...*

I discovered an error in one of the formulas this morning, so I thought I would start a thread for discussion of any errors that anyone else comes upon. 

There is an error in the power PE reference handbook. The formula for capacitance required to change the reactive power on page 65 is missing a “2” in the denominator as the whole formula’s denominator should be “ω*(Vline)^2”, where ω=2*π*f as referenced in the handbook on page 35. Please refer to the attached pictures. The textbook picture is from page 482 in “Fundamentals of Electric Circuits by Charles K. Alexander and Matthew N.O. Sadiku Fourth Edition.

It appears we will have to do their QC for them to make sure all formulas are correct.


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## Orchid PE (Sep 13, 2020)

We covered this in another topic. It's not a mistake, notice the line above the formula that says "maximum value of the sinusoid" and not "RMS value."


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## DilutedAr18_PE (Sep 13, 2020)

Chattaneer PE said:


> We covered this in another topic. It's not a mistake, notice the line above the formula that says "maximum value of the sinusoid" and not "RMS value."
> 
> http://engineerboards.com/topic/35795-just-got-an-ncees-email-saying-october-pe-exams-are-canceled/?do=findComment&amp;comment=765


Just found that. Why would you define Vline as Vmax? There is no reason to redefine variables where it makes your formula shorter. Use the typical formulas found in textbooks.


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## Orchid PE (Sep 13, 2020)

DilutedAr18 said:


> Just found that. Why would you define Vline as Vmax? There is no reason to redefine variables where it makes your formula shorter. Use the typical formulas found in textbooks.


Totally agree. It's a little odd they did that.


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## speakeelsy PE (Sep 13, 2020)

Other mistakes that we've discussed in Zach's class and on the forums:

4.3.1.6 Single-Phase transformers in Parallel - %ZT1 and %ZT2 are switched in the formulas on page 60

4.3.1.7 Autotransformers - in the last equation NC in the denominator should be NSE page 61

and I think it was mentioned in another thread that the connection diagram for the ungrounded wye-delta zero sequence network includes a ground - page 68


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## akyip (Sep 22, 2020)

Hey guys,

I think I may have found another possible mistake in the reference handbook. This time it concerns illumination.

My first attachment shows the formula and diagram in the reference handbook. It uses the straight-line distance D in the denominator, but after doing a few practice questions... shouldn't the denominator be (D')^2?

My second and third attachments are from the Shorebrook PE Exam Question 11, which uses the actual distance between the fixture and the point of illumination.

I also briefly Googled this cosine law of illumination, and it also uses the actual distance between the light fixture and illumination point (not the perpendicular straight-line distance to the plane).

Can someone else verify this? Thanks!


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## DilutedAr18_PE (Sep 26, 2020)

akyip said:


> Hey guys,
> 
> I think I may have found another possible mistake in the reference handbook. This time it concerns illumination.
> 
> ...


I think you understand how to use the formula. They have attempted to simply the formula from a form with no angle and a formula with an angle. The formula without the cos(Θ) is the inverse square law. With the cos(Θ) is the inverse square cosine law. When Θ is 0 degrees, the cos(Θ) is 1 and the distance would be D. If Θ doesn’t equal 0, then you would use D’ as your distance. 
 

I am going to send in a comment to NCEES to have them remove the “x” from the formula, because that is really only meaning multiply, but “x” is used as a variable in many other instances. 
 

I have attached a picture of page 36 from “Illuminating Engineering” 2nd Ed. By Joseph B. Murdoch. He takes a little more liberty in not stating the exact formula he uses by using the Pythagorean Theorem (squaring the two dimensions of the vertical and horizontal distances and thus eliminating the ^2 in the denomination), but it is the same formula.


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## Garrett C (Nov 9, 2020)

There are several more errors in the handbook.  I emailed them over a month ago but they have not fixed any of them.  I see they have revised the handbook to revision 1.1.1 but I couldn't tell you what they actually changed.  Perhaps if any of you feel motivated you could email them as well?  Maybe if enough people bug them they might fix things before the test day??  It will drive me nuts in the middle of the test not knowing if I should use the equations they give even though I know them to be wrong.

*Page 21  *The ND=........ equation does not yield events/year as they stated.  It yields events/year x 10^-6.  See NFPA 780 page 82 for reference.

*Page 30 *The equation for R2 is missing an exponent of 2.  See IEEE standard 80-2000 for reference.

*Page 34 *In the equation for Base Impedance the denominator units should be in KA not A since the numerator is in KV and the result is in Ohms.

*Page 48 *The second i0(t) equation is missing a minus sign.  Google a paper by Dr Firas Obeidat page 13 for the correct equation.  This equation is also on page 334 of the Hart power electronics textbook but the minus sign is in the wrong spot in Hart equation.  If you graphed the results of these equations you would see that only the Obeidat equation is logical.

*Page 58 *The diagram shows Rc and Xm but in the description of each variable they define them using the wrong subscripts (Ro and Xo).

*Page 61 *This one is hard to see at first glance (you might need to zoom in) but they have the equation as L=N^2uA/1.  It should be L=N^2uA/l.  In other words the number "1" should be a lower case "l".

*Page 75 *The power curve picture shows Pc but it should be labeled Pe


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## akyip (Nov 9, 2020)

Guest Garrett C said:


> There are several more errors in the handbook.  I emailed them over a month ago but they have not fixed any of them.  I see they have revised the handbook to revision 1.1.1 but I couldn't tell you what they actually changed.  Perhaps if any of you feel motivated you could email them as well?  Maybe if enough people bug them they might fix things before the test day??  It will drive me nuts in the middle of the test not knowing if I should use the equations they give even though I know them to be wrong.
> 
> *Page 21  *The ND=........ equation does not yield events/year as they stated.  It yields events/year x 10^-6.  See NFPA 780 page 82 for reference.
> 
> ...


Aw man, if this list of errors really is true, add this to the list of headaches with having to rely on this reference handbook for the actual PE exam. I'm a bit worried...

Another thing that kind of worries me is that there are a good amount of formulas and concepts in the reference handbook that I've never had to use for many practice exams... If they require having to use one of these formulas/concepts and I don't know how to properly use it, I'm going to have to wing it...


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## Dothracki PE (Nov 10, 2020)

There is stuff on the reference sheet that is not in practice exams, there is stuff on the practice exams that is not on the reference sheet. We are unfortunately caught in the period where the practice exams lag behind the changes to the exam.


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