216 



ELECTRICAL ENGINEERING 



Fig. 182 shows the characteristic curves of a 75-h. p., 600-volt 

 railway motor built by the General Electric Co. 



Fig. 183 shows the characteristic curves of a 500- volt crane 

 motor built by the Crocker Wheeler Co. Its rated output is 65 

 h. p. for J hour with a temperature rise of 40 C. 



Fig. 184 shows the characteristic curves of a 25 h. p., 500-volt 

 compound-wound motor of the Westinghouse Co. 



100 50 

 90 45 

 80 40 



& M 



70 g 35 



3 w 

 SGO - so 



50 g 25 



30 15 



20 10 



10 5 







4000 



3500 



3000 



2500 



2000 



1500 



1000 



500 



20 40 60 



FIG. 182. Characteristic curves of a 75-h. p. railway motor. 



100 120 140 ICO 180 200 220 240 

 Amperes 



132. Limits of Output of Electric Machines. The factors 

 which limit the output of electric machines are 



(1) regulation, 



(2) efficiency, 



(3) heating, 



(4) sparking. 



(1) In motors the regulation is a speed regulation. With in- 

 crease of load the speed falls off and the increased torque is ob- 

 tained at a decreased speed. In constant-speed work the shunt 



