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While doing VD problems, my instinct will say to use (5+15j) * 30 < -36.86 = 474.34volts which i think is the most accurate one. And choose the most near one option. I know the difference is too much but no other way. If got extra time in exam to check then will apply VD = I (RCosφ + XSinφ)...

It depends on which phase to phase fault occurred. IA=0 if there is Phase B to Phase C fault.  Here in this problem phase A to phase B fault occurs so condition will be IC=0.

I appreciate your views on this. Here is mine. First i thought it should be 72A because of the statement in NEC 460.8 "The ampacity of conductors that connect a capacitor to the terminals of a motor or to motor circuit conductors shall not be less than one-third the ampacity of the motor...

Question: "A three-phase transformer bank is to handle 500 kVA and have a 34.5/11-kV voltage ratio. Find the rating of each individual transformer in the bank (high voltage, low voltage, turns ratio, and apparent power) if the transformer bank is connected to open wye—open delta." My ans: HV...

         Sout = (Pout_pu + jQout_pu)•|Sb|          Sout = Pout_pu•|Sb| + jQout_pu•|Sb|           Pout = Pout_pu•|Sb|   and Qout = Qout_pu•|Sb|   I really appreciate your explanation. Thank you @Zach Stone, P.E.  for enlighten us. The above statement elucidate my confusion...

"what would be the advantage if you were to reconnect a conventional voltage transformer as an autotransformer ? " As you can see the question is mentioning to reconnect the same transformer as auto-transformer. If you reconnect the same transformer there is no logic to get less wingdings. So...

Found somewhere in the board, may be useful for discussion. "If a motor with 60A needs a feeder ckt of 1.25*60=72A  and a capacitor rated for 60A is connected somewhere near motor terminals ( A hypothetical case for understanding purpose only), will the motor feeder ckt conductors now required...

Let say a conventional transformer is  rated 10kVA. If we use this same 10kVA transformer  and connect it to auto transformer connection, its rating can goes max. say 60 kVA (depends on connection). Hence it can handle more power. But if you are comparing 10 kVA conventional transformer with...

Interval #2 Area; A2 = (25kW x 15min)+ (1/2 x 25kW  x 15min) = 562.5 kW min Interval #2  time interval; t2: 15 min. Avg power in interval 2 = A2/t2 = 562.5 kW min / 15 min = 37.5 kW Does it make sense now?

At first, Base apparent power 500MVA multiply with pf will lead to base real power not actual real power. For actual real power, base real power shall be multiply with its pu value. Regarding calculation, can we multiply or not? I think we must. If we ignore it, our answer will be 667MVA which...

If you find the source for this statement please post it here for our reference. My view: MVA & MW are same only for unity pf.  So may be the case taken on that situation only. Need to see the whole statement for the conclusion.

Sorry to say i don't have the answer for this. I got this question from the internet "chegg.com".

Question states "Which breaker(s) would be most likely to provide back up protection for breaker #4?". Ans in the book is option b. 2, 7 & 6 I understand the other options in the book were not valid so the correct will be option b. But lets say we don't have any options then i think the...

I think you mean to say both active and reactive power.

Pleas let me have your views on this.

@eatsleep: Thank you so much for your confirmation.

@Messi I appreciate your point of view.

@roy167 & @eatsleep: I don't think it is correct. Here the power consumed by the inductive load is 667 MVA which is greater than the capacity (500 MVA) of Syn Gen. Let me make few changes on your post. They have given 0.8 PU real power and Power factor of 0.6 (Cos Q).  Let Base MVA  =500...

Graffeo Ex 53: In this example, for Double line to ground fault current only Ib is considered here which is incorrect. I think the fault current shall be "Ib+Ic" or "3 x Ia0" which will lead to the answer "j10.71". Please correct me if i am wrong.

Lets say Sbase is gen MVA, but what is the logic of getting Zpu of generator by dividing transformer MVA to Sbase. I don't see any logic. Can you please elaborate more?