36 



ELECTRICAL ENGINEERING PROBLEMS 



20 mils. Required the eddy current constant to give the stated 

 loss in watts. (The thickness is to be kept in mils.) (10 min.) 



10. A 110-volt, 100-ampere armature has a resistance of 0.025 

 ohm. Plot a curve of loss in the conductors with current; give 

 the equation for the resulting curve and its name. If the machine 

 be a long shunt compound, 100-volt generator, with the series- 

 field resistance 0.01 and the shunt-field resistance 25, plot the field 

 losses and the total copper loss with current in the outside circuit 

 as abscissae. (10 min.) 



11. A 1000-kw., 1000-volt generator has 1000 r.p.m. rated 

 speed. The armature resistance is 0.106 ohm. When run as a 

 motor with normal field strength it takes 925 volts on the armature 

 to give normal speed and the armature current is 22.2 amperes. 

 What is the stray power? (4 min.) 



12. In the generator of problem 11 the other resistances are 

 series field, 0.002; interpole, 0.0035; the shunt current is 2.24 

 amperes and the brush drop (both sides) is 2.8. Required the 

 efficiencies for J, J, f, 1 and 1J load. Plot these as a curve with 

 output as abscissas. (15 min.) 



13. A 100-volt shunt motor has the resistance of the armature 

 0.03 and of the shunt 20 ohms. The full load on the armature is 

 10-kw. input. When the motor is run on no load at full-load speed, 

 the armature takes 4 amperes at 90 volts. Required the full-load 

 efficiency. Neglecting the change in stray losses, find also the 

 f , J, J and T V load efficiencies and plot with input. (15 min.) 



14. A test of a 2J-h.p., 110-volt shunt motor gives the following 

 resistances: Armature 0.3, field 55. 



The results of the speed load test are: 



ARMATURE 



The results of the iron- and friction-loss test are : 



