# ncees exam 518



## Sparky Bill PE (Dec 2, 2020)

Why do I take the peak voltage before doing my calculation instead of just using my RMS? Is this some battery thing I don't know about where the 60V on the other side is considered a "peak" voltage?


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## akyip (Dec 2, 2020)

From my understanding, I think it's because you are asked to limit the MAX or PEAK charging current. Hence, you also have to use the MAX or PEAK input voltage...


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## speakeelsy PE (Dec 3, 2020)

it's a rectifier so your AC in will be DC after the rectification. When you rectify AC into DC, your DC out of the rectifier circuit is a function of your ACmax voltage, not your ACrms voltage. 

If it helps, imagine the rectifier as a DC source using the 3phase rectifier formula on page 47 and redraw the circuit.

Does that help?


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## rburns18 PE (Dec 5, 2020)

I was curious why the 294.2V wasn't multiplied by .955 like shown on page 47 of the handbook.


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## Art (Dec 13, 2020)

Vdc = 3 sqrt2 208/Pi =280.9

280.9 - 60 = 220.9/10 = 22.1 Ohm

22.1-2.5 = 19.6 Ohm

btw 0.955 x (sqrt2 x 208) = 280.9

0.955 = 3/Pi


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## Sparky Bill PE (Dec 13, 2020)

Thanks for response, I passed the PE so thank the LAWD I don't have to deal with this anymore lol


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## rburns18 PE (Dec 13, 2020)

Art said:


> Vdc = 3 sqrt2 208/Pi =280.9
> 
> 280.9 - 60 = 220.9/10 = 22.1 Ohm
> 
> ...


That is what I get when I use the 1st equation you have there. I think that is how they should solve it going forward so they are following the Handbook.



Sparky Bill said:


> Thanks for response, I passed the PE so thank the LAWD I don't have to deal with this anymore lol


I'm taking it the 21st. Hoping to be in the same boat as you very soon!


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## Sparky Bill PE (Dec 13, 2020)

Rburns18 said:


> That is what I get when I use the 1st equation you have there. I think that is how they should solve it going forward so they are following the Handbook.
> 
> I'm taking it the 21st. Hoping to be in the same boat as you very soon!


YOU GOT THIS YOU GOT THIS! Hard work! I had over 500 hours studied and 2,500 hundred problems worked so I came in very prepared for it lol!


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## rburns18 PE (Dec 13, 2020)

Sparky Bill said:


> YOU GOT THIS YOU GOT THIS! Hard work! I had over 500 hours studied and 2,500 hundred problems worked so I came in very prepared for it lol!


Thanks! I started preparing last November for it in preparation for the April 2020 exam and now here we are. Since I have you here, I have the following practice exams:


Cram Vol I-IV

Engineering Pro Guides Final, Full and Reference Exam

ElectricalPEReview Exam and the start of the new AIT exam

Graffeo

Complex 1-4

NCEES Practice Exam

Have done about 2 of the Spin Up exams

I really enjoy the ElectricalPEReview and Engineering Pro Guides exams. The Cram exams are good since they are tough/have a lot of qualitative questions but at the same time a little discouraging because of the difficulty. It's a little late now probably but are there any other practice exams I should be looking at? I don't think those above get to 2500 problems. I have an older copy of Camara exams but a lot of the info seems out of the scope of the PE Exam. Was there an exam you found most helpful? I'm also using Wildi, Chapman, Glover, and Stephenson textbooks for theory.


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## Sparky Bill PE (Dec 13, 2020)

My 2,500 problems also comes from working every single problem Zach Stone has released, twice. I made a spread sheet where I went through every single module, every quiz on his website, twice.... 

My honest opinion is to hammer down easier problems to get a good foundation, so I really enjoy complex imaginary problems don't feel u have to do a "timed test" I would sit down and hammer out 40 at a time. 

The white boon NCEES practice exam you should LITERALLY be able to work EVERY PROBLEM, and work that entire exam 3 times. 

Work every NEC problem you can get your hands on.


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