CH. V SERIES-WOUND MOTOKS 115 



It is important to notice that these equations refer to 

 conditions in which the load per motor remains the 

 same, and when it is stated that the motor is connected in 

 series with a second similar motor, it is assumed that the 

 load on the first motor is unaltered, and that there is an 

 equal load on the second motor. 



This may be clearer if the equation is expressed in 

 terms of the torque on the motor. Suppose that we have 

 two motors. Let t be the torque in inch-pounds per motor, 

 E the tension of the line. R the resistance of each motor. 

 The induction factor corresponding to the torque t can 

 be found from the induction curve, since for steady running, 

 the torque determines the current and the induction factor ; 

 in other words, if the torque is given and we have the 

 induction curve, we know what must be the induction factor 

 of the motor when it is running at a uniform rate. Hence 

 we can write 



Speed in parallel = n., =| ^-0-71~ ...(47). 

 M M* 



also 



Speed in series = w s = ^. 0-7 1 ..... (48). 



We thus see that 



so that the speed when the two motors are connected in 

 series is less than half what it is when they are connected 

 in parallel, by an amount depending on the load on each 

 motor. 



i 2 



