COMMUTATING ALTERNATING CURRENT MOTORS 353 



and is used to a limited extent for this purpose. The 

 most notable example is the New York, New Haven & Hart- 

 ford R.R. which has been operating for several years with 

 single-phase series motor locomotives. It seems to be 

 fairly successful in this installation but because of its inferi- 

 ority to the c-c. series motor, it is not likely to come into 

 extensive use. 



102. A-C. Series Motor vs. C-C. Series Motor. At 

 present, nearly all electric railways in this country use the 

 continuous-current series motor as their motive power. 

 The distribution of the electric power from the generating 

 station to the car wheel is inefficient because of the many 

 steps involved. 



Losses in a System Using C-C. Motors. The power is 

 generated as alternating-current, goes through step-up 

 transformers at the station to the high-tension trans- 

 mission line and so to the substation; there it goes through 

 step-down transformers, to the synchronous converter 

 where it is changed to c-c. power and is sent out through 

 the c-c. feeders and trolley to the car. The speed control 

 of the series motor requires the use of rheostats and con- 

 siderable power is used up in these as well as in all the 

 other parts of the system just enumerated; probably not 

 more than 45%* of the power generated in the main station 

 is delivered to the car wheel. 



The system of distribution and probable losses in each 

 part of the system are given in Fig. 229; the different 

 percentages given show the approximate loss of power 

 in that part of the system. These figures will vary widely 

 for different installations. 



Losses in System Using A-C. Motors. In case the 

 alternating current series motor is used on the car the 

 power distribution is much simpler. At the station there 

 may be a step-up transformer connected directly to the 



* Of course, this figure will vary widely in different installations, 

 depending upon the type of apparatus installed, schedule of cars, etc. 



