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But you failed to mention how you have a "circuit" in a 3-phase, 3 wire system.  As mentioned above, this is where sqrt 3 rears itself yet again, and the circuits are made on another phase (cyclically alternating...i.e. A-B-B-C-C-A, for example, where A returns on B, B returns on C etc.)

Actually, 3-phase is not 1, rather it is 1.732.  It still has to return to the source.  It doesn't hit an arbitrary load and stop there.  How does it return on a 3-phase system, you ask?  On another phase (although, the imbalance returns on the neutral, if in fact it is a 3-phase, 4-wire system).  

The entire coil is NOT used in transferring power from primary to secondary; hence, the KVA of an autotransformer, depending on design, can be sunstantially higher than a two-winding, single phase XFMR.   Just as with the example you provided, 125A is delivered to the load through the 120V...

Or you can look at it this way, which is much easier and saves a butt load of time, thought and work... (VH + VL)/VL= 5, where this is V high (480V) and V low (120V) 5 x (15 KVA) = 75 KVA The math in the diagram is correct, but the labeled currents are wrong.  Swopp I2 and I3.  I2 being 125...

What Owism said.  There's a mountain of info on that forum.  That said, I self-studied cause I didn't see the need to spend money on a course that couldn't prepare me in the manner I could prepare myself (i.e. presentation, types of problems, methods for solving, etc.).   As for me, the...

Fortunately, I've already taken and passed the exam; but I prepared and studied vigorously.  I found the exam to be a fair representation of the material outlined by NCEES.  That's not to say it was easy, cause it wasn't, but it was about what I expected with regards to concepts and intuitive...

Power electronics will be presented in some capacity on the test (re: outline on NCEES website).  As for your second question, I don't have an answer for you as to why it was worked that way without having more info.  Could be a mistake on their part...?

The PE is not as ambiguous as the above situation.  Yes, it will force you to use some intuition and make some assumptions, but it alleviates ambiguity to that extent.  To be honest, the PE is more about concepts, concepts, concepts!  Not how well do you integrate and "guess" what I'm...

Actually, on second thought, my initial approach may be incorrect.  I'm inclined to think your approach may be the way to go.  

Pardon the typo in my previous post.... should read infinitesimal, not infitesimal.  @BigWheel, the work was spot on and much more elaborate than I could show by manually entering via a phone.  I've tried to attach pictures and clips before, but the files have been too large and I'm never in a...

Avogadro's number

BigWheel wasn't exactly right... The integral should be: (1/T)S(sin(wt))dt --where S is the integral and evaluate this from 0 to pi. Inherently, it is evaluated over one half cycle, since a full cycle would yield an average of 0 (i.e same curve area above and below and it would reduce to 0)...

As @BigWheel said, the given expression is for one phase (call it A).  The subsequent phases would be the same with an argument of (wt-120) and (wt-240/or+120), respectively. Remember, if you are asked for an average, you will almost always integrate. In some instances, integration may not be...

Also, since the firing angle is at 0, the waveform is a purely sinusoidal input (it is not chopped at pi/6, as would be the case if it were at 30 degrees).

I'll try to point you in the right direction:  First, it is rectified, so we are taking an AC input and getting a DC output.  The given equation is an instantaneous expression for the voltage, v(t), where 460 is the amplitude (peak) of the voltage waveform (no need to multiply/divide by sqrt2...

Yep, agreed!  I don't understand the "shock."  If you're shocked after taking a course and struggling with the test, your approach was entirely insufficient.  Having good materials and knowing how to use them, I would argue, is  more valuable than any course money can buy.

Seems everyone is focused on a course rather than focusing on what works for them.  Personally, I did not take a formal course.  I didn't want to spend the money, and also, no one knows me and my abilities better than I do.  I will go on the record and say that no course will be a 100% lead pipe...

Cheaper on gas

I told my wife that and....well... umm if looks could kill, I wouldn't be here telling you that.

There was no confusion, just cage rattling.