DIRECT CURRENT RAILWAY MOTORS 



83 



COMPLETE TESTS consist of special tests, thermal 

 characteristics, commutation and input-output. With 

 the exception of commutation, the other tests under 

 this heading will be considered separately. 



Commutating tests on series railway motors should 

 be made by holding normal voltage and operating the 

 machine at loads varying from 33 J^ per cent to 200 

 per cent normal load. 



400 300 



30O 600 

 200 



JOO 200 



QO /2O /60 ZOO 24O 

 /l/nperes 



Fig. 24. Core Loss and Speed Curve of a 50 H.P., 500 Volt Railway Motor 



On series commutating pole motors, interruption 

 tests are taken. These tests consist in opening and 

 closing the motor circuit while the machine is running 

 at various loads and speeds. The machine should 

 stand such tests without arcing over at line voltage as 

 high as 125 per cent normal. The loads are varied 

 from 33 J^ per cent to 200 per cent normal. Mill motors 



