110 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



at 0.7 power factor, and the third is 30 kilowatts at unit power 

 factor. The high-tension line voltages are 600 volts. Neglect 

 the losses in the transformers. What are the high-tension line 

 currents? 



32. Three unequal single-phase motor loads are connected 

 across the lines of a balanced 3-phase, 230-volt circuit. The first 

 takes 106 amperes at 0.78 power factor, the second takes 142 

 amperes at 0.82 power factor, and the third takes 28.4 kilowatts 

 at 0.77 power factor. What are the line currents? 



33. Three unequal single-phase motor loads are connected 

 between the lines and neutral conductor of a balanced 3-phase, 

 350-volt circuit. The voltages from the lines to the neutral are 

 each 202 volts. The first load takes 20 kilowatts at 0.82 power 

 factor, the second takes 28 kilowatts at 0.75 power factor, and the 

 third takes 36 kilowatts at 0.79 power factor. What is the 

 current in the neutral conductor? 



34. From the terminals of a 3-phase, 550-volt, 60-cycle 

 alternating-current generator runs an artificial transmission line 

 which has a resistance of 0.1 ohm and an inductance of 1.0 milli- 

 henry per conductor. At the end of this line is a balanced load of 

 three reactors connected in Y. The equivalent resistance and 

 reactance of these reactors should be assumed to be constant. 

 The power output of the generator is measured by the two-watt- 

 meter method with the current coils of the instruments in lines 1 

 and 2. The first wattmeter indicates 40 kw. and the second, 

 100 kw. 



If line 3 is opened at the load what power will the instruments 

 indicate? The terminal voltage of the generator is constant. 



35. In problem 34 if line 3 is opened between the terminal 

 of the generator and the potential coils of the wattmeter, what 

 power will the instruments indicate? 



36. From the terminals of a 3-phase, 500-volt, 25-cycle alter- 

 nating-c n rrent generator runs an artificial transmission line which 

 has a resistance of 0.3 ohm and an inductance of 3 millihenrys 

 per conductor. At the end of this line is a balanced load of three 

 reactors connected in delta. The equivalent resistance and 

 reactance of these reactors should be assumed to be constant. 

 The power output of the generator is measured by the two- 

 wattmeter method with the current coils of the instruments in 

 lines 1 and 2. The first wattmeter indicates 50 kw. and the 

 second, 25 kw. 



