224 



THE DIRECT-CURRENT MOTOR 



CH. X 



energy expended in covering the given distance under 

 different conditions : 



We assume that the accelerating current from the line 

 remains the same, hence the best diameter is obtained from 

 Equation 102 by using the numerical constant O834. The 

 time occupied has been worked out by taking each step 

 separately. 



In obtaining these results we have assumed the accele- 

 rating current from the line to be constant throughout the 

 period of acceleration. Thus in the case when the diameter 

 is 44'2 inches, cy=31 amperes; the accelerating current 

 per motor when the motors are in series is 169 amperes, 

 the acceleration is 1'lGl f.p.s. per second, the distance 

 travelled is 74 feet, and the time is 1 1 seconds. When the 

 motors ai*e in parallel the accelerating current per motor 

 is 09 amperes, the acceleration is 0'473, the distance 



