NCEES #118 - why no SQRRoot of 3?
Shouldn't there be a multiply by 1.732 in this solution? In problem 506 there is...it is voltage not current but still.
The only thing I can figure is that it is Line to Neutral current vs. Line to Line current.
Any thoughts?
Have a look at this
thread.
Based on what the problem is asking, the circuit can be simplified by eliminating the 2nd xfmr circuit since we are being asked to find the generator current. So now all you have is a generator and xfmr with a j20 Ohm transmission line. By rule of thumb for a transformer, Igenline / Itransline = N2 / N1 --> Igenline = 75.93A x 132 / 13.2 = 759.3A
EDIT: In addition, sqrt(3) is already factored into the turns ratio. Another way to look at this would be convert the secondary voltage to L-N voltage which would be 132kV / sqrt(3) = 76.2kV. Now to get your primary line current on the delta side, VL-N = VL-L. So your turns ratio equation for a xfmr becomes (76.2 / 13.2) x 75.93A = 438.3A (phase current). Now covert to line current for the delta side by multiplying by sqrt(3) which yields the same 759.3A. By using 132 / 13.2 as your turns ratio, sqrt(3) is already factored in. Does that make sense or did I not explain it well?
