DIRECT CURRENT RAILWAY MOTORS 



87 



normal full load excitation. The armature of the gen- 

 erator is connected to a water box, the resistance of 

 which is varied until full load on the motor is obtained. 

 The run is made for one hour, after which temperatures 

 are taken. 



Resistances are measured and high potential applied 

 both before and after the test and before starting. 

 The speed should be checked in both directions of 

 rotation. 



Bwster 



Fig. 27. Connections for Running Light on a Railway Motor 



One out of every fifty of all types of motors should 

 receive the one hour load run. All 600 volt commutating 

 pole motors, with the exception of those receiving the 

 one hour load run, should be run under load for ten 

 minutes in each direction of location. Other motors the 

 characteristics of which are well established should 

 receive "commercial tests." 



Commercial tests consist in running a motor light 

 for a short period. It is the practice to run four motors 

 in parallel, the fields being connected in series and 

 separately excited by a current equal to the full load 

 current of the motor. (Fig. 27.) 



