CHAPTER XIV 

 DYNAMO LOSSES AND EFFICIENCIES 



1. A 10-kw., 110-volt, 2-pole shunt generator has the armature 

 resistance 0.04 and the shunt field 22. Required the copper loss 

 at full load. The field rheostat resistance is 15 ohms. If tin- 

 machine gives 110 volts at no load with this resistance all in, 

 required the no-load copper loss under these conditions. (4 min.) 



2. A 500-kw., 550-volt generator requires 2.10 volts to send 

 200 amperes through its armature when at rest. What will be 

 the armature copper loss when giving its full-load current of 910 

 amperes at 550 volts? (3 min.) 



3. A 500-volt, 4-pole, 35-kw. generator (500 r.p.m.) has rr> 

 ances as follows: Armature, 0.3; shunt field, 200; series, 0.15. 

 Required the copper loss for a load of 60 amperes. (4 min.) 



4. If in the generator of problem 1 the iron losses constitute 

 2%, and the friction loss 3% of the rated output, required the 

 efficiency at full load. Also for J load, assuming the speed to 

 remain constant, and that 8 ohms of the rheostat are in the field 

 circuit. (8 min.) 



5. In the generator of problem 3 if the hysteresis loss be 140 

 watts, that due to eddy currents, 50 watts, and if the friction loss 

 be 1\% of the rated capacity, required the efficiency of the machine 

 for- a load of 60 amperes. (2 min.) 



6. If the machine of problem 6, Chap. XIII, has a brush-con 

 resistance = 0.003, series-field resistance = 0.0008 and shunt -field 

 resistance = 60, required the total copper loss for no load and for 

 full load. (4 min.) 



7. If in problem 6 the total friction loss be 5 kilowatts, required 

 the full-load and half-load efficiency. (6 min.) 



8. In the generator of problem 6, Chap. XIII, the outside diam- 

 eter of the armature disks is 83.5 cm., the inside diameter 45.7 cm., 

 the depth of a slot 4.13 cm., and the iron length of the core 22.8 

 cm. Also the mean density is 10,700. Required the hyst : 

 constant to give the hysteresis loss as stated in watts. 



9. The thickness of the disks in the generator of problem 8 is 



35 



