302 



ALTERNATING CURRENTS 



phase power is less than the average power. In practice the 

 actual speed variations of the armature are slight. 



The electric locomotives of the Norfolk and Western Railway 

 are operated by the use of a phase converter. A two-phase 

 converter is used, as only half the power need be converted under 

 these conditions, the other half flowing conductively from the 

 transformer secondary to the motors. The power is received 

 single-phase from an 11,000-volt trolley and stepped down by a 

 transformer on the locomotive. Special transformer taps are 



To Driving 



Motors 



Motors 



FIG. 280. Connections of locomotive phase converter. 



used to keep the phases balanced. The general diagram of 

 connections is shown in Fig. 280. It will be recognized that the 

 converter and transformer connection is equivalent to a T- 

 connection. This is used in order that three-phase power may 

 be obtained by supplying single-phase power to the two-phase 

 stator of the converter. The phase ab to the driving motors is 

 supplied directly from the transformer. The winding a'b"b', 

 tapped to winding ab, is the main winding of the phase converter 

 (see Fig. 207, page 217). The winding c'c"c is the teaser winding 

 tapped to the transformer at c', giving the third wire c of the 



