Errata - Jan 2015 Printing:
There is an error in the PT section of the book that will be corrected in the next printing:
There is a Copy & Paste error. Where it says:
“Just as in CTs, never open the secondary of a PT while current is flowing in the primary circuit, as large periodic secondary voltages develop during periods of flux change. Because of this, if a meter or relay secondary circuit of a PT must be disconnected, you must first short-circuit the secondary winding, and then remove the component. The short across the secondary winding may be removed after the secondary circuit is closed”
This is incorrect information.
While the secondary winding may seem to be isolated from the primary winding, There may be large voltages built up due to the distributed capacitance. Never short circuit the secondary winding. As this may lead to a fatal shock.
P 4 The RMS formula should be:
P 8 ex. 2, The concepts shown in this problem are correct. However for this size load & generator, we should be using a three phase solution:
P 9, Ex 2.
Vp should be as follows:
On page 21, I should have been more specific on my formulas:
P 23 334.49 should be in VA, not W
Calculation should say 87.34 angle -11.3 V (not Amps)
P 26 ex. 12 Power should be in KW not KVA
P45 The dot on the secondary coil for the subtractive polarity diagram should be on the lower right.
P 49 - Ex. 22 Should say 4% - 0.3 = 3.7%, So the range will be 3.7% to 4.3%
P 54 It should say:
P 65 Ex 30.
Coil pitch = 20 deg X 8 = 160 deg
P 69 Ex. 31 The final answers are correct but the lagging pf angle should be +35.9 deg, the leading pf angle should be -35.9deg.
P 71 Ex. 32b is incomplete:
P 81. Use THHN CU wire. It should be 28A X 125% (for cont motor loads) = 35A
P 127 I missed the generator impedance on this one. The positive sequence impedance should be 0.2 + j0.546 instead of 0.2 + 0.466