Problems

Author: E.E. Kimberly

	Problem	Answer
1	A factory load of 1200 kv-a, 440 volts, 62% power factor lagging is to be increased with improvement in power factor. With an efficiency of 90%, how many horsepower in synchronous motors operating at 80% power factor leading would be required to correct the over-all power factor to 85% lagging?
2	A 3-phase synchronous motor rated 100 hp, 440 volts, 0.8 power factor, 140 amp, 60 cycles has a synchronous impedance per phase Zs - 0.0931 -j0.3477 ohm, which is assumed to be constant. When the motor is running at its rated load and power factor, what is the generated voltage Ea per phase? Graphical solution is suggested.	276 volts
3	Calculate the windage, friction, and iron losses of the motor running as described in Problem 2	4926 watts
4	If the loss in the d-c field of the motor of Problem 2 is 4000 watts, what is the efficiency when operating as described?