Problems
Author: E.E. Kimberly

Problem 
Answer 
1 
A factory load of 1200 kva, 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 overall power factor to 85% lagging? 

2 
A 3phase synchronous motor rated 100 hp, 440 volts, 0.8 power factor, 140 amp, 60 cycles has a synchronous impedance per phase Z_{s}  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 E_{a} 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 dc field of the motor of Problem 2 is 4000 watts, what is the efficiency when operating as described? 

