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What has locked rotor amps to do with sizing of disconnect switch? 430.110 (A) says the disconnecting means to be " not less than 115% of FLA" Any comments?

Understand a raw score of 50% is sufficient. Best of luck

The difference is in Phase Voltage to Line voltage. Considering only reactive load:- single phase VAR = V-LN * I Three phase VAR = Sqrt 3 * (V-LL) * I = Sqrt 3 * (Sqrt 3 * V-LN) * I = 3*V-LN*I = 3* I*X*I = 3I^2*X

Third harmonic is a triplen harmonic. Odd harmonics add up in neutral. Harmonic currents are routed through neutral. In this case, harmonic curents in each phase route through neutral therfore current is additive in neutral. 3X 3 = 9amp Does anyone know what happens in 3 phase three wire systems?

Follow up on flyers answer: Just up the Y side voltage by mutiplying with sq.rt. 3 in such case.

There is an easier way to solve this using MVA method as follows: Transformer SCMVA = 7.5/.075=100 MVA Transmission Line SCMVA = kV^2/Z=144/15.312 = 9.40 MVA Two impedance sources are in series. Hence SCMVA at fault = 9.40X100/9.40+100 = 8.59 MVA Ifault at Fault location I =...

Yes you can mix both polar and cartesian complex numbers. I use it all the time. This is the best calculator out there. I used it for EIT. Many problems were solved by just entering the numbers. The problem is with -60, this can not be negative.

Remember, the Voltage P-N always lags the Voltage P-P by 30 degrees. Hence Voltage P-N angle is (-30)