CH. XI DESIGN OF KAILWAY MOTORS 253 



feet per second or 25 '6 miles an hour. The highest speed 

 actually attained is 23'6 miles an hour. 



The acceleration curve has been continued up to the 

 point when 1,930 feet has been covered, corresponding to 

 the point at which the brakes were put on in the experi- 

 ment ; the curve gives 76 seconds as the time occupied, 

 compared with 77 seconds in the test. The time taken to 

 cover 2,000 feet is 78 seconds by the curve, being 2'5 per 

 cent, less than the time calculated, the difference being 

 due to the use of series winding. 



In Fig. 63, vertical ordinates represent current from 

 the line, the dotted curve giving the results of the 

 test of which the acceleration curve is given in Fig. 62. 

 The calculated current curve is shown by a full line ; 

 the motors are in series for 7 seconds, during which time 

 the current is 257 amperes ; they are in parallel, taking 

 257 amperes each, or 514 from the line, for about 7 

 seconds longer ; the current then rapidly decreases : points 

 on the curve are found from curve A in Fig. 61. 



The irregularities in the experimental curve are the 

 results of the uneven handling of the controller. We see 

 that the motors were taking about 380 amperes each at 

 the start, and were allowed to speed up in series for about 

 10 seconds after the starting resistance was taken out. 

 When thrown into parallel the current per motor is about 

 330 amperes per motor, or 660 from the line. The form 

 of the current curve as the motors speed up in parallel is 

 well shown. More careful manipulation of the controller 

 would have effected a better start. The dip in the 

 acceleration curve during the period from 10 to 40 seconds 

 might have been avoided by not allowing the motors to 

 speed up in series. 



