Kinsley — Discussion of Series Dynamo-Electric Machines. 113 



In the case of any series machine if x and y be plotted and 

 found to give a straight line then it is true for that machine 

 that a and b are constants according to the assumptions. 



Equation (4) can also be arranged 



ni 

 Here as in (5) if a plot of i and ^ give a straight line then 



a and b must be constant. 



Fig. 3 gives this relation for five points taken from the 

 characteristic. See also fig. 13, fig. 15, and p. (127). 



a and b may be gotten by solving the following equations : 

 1 , . 6 ni 



-+ 1 — = rT 



- + 100 - = 200 

 a a 



L + 20 - = 154.4 

 a a 



See fig. 3. 



a = 0.007 

 b = 0.004 

 Equation (4) becomes 



(7) E= 0-0°'"' 



1 + 0.004 i 



Equation (7) is the characteristic equation of this series 

 dynamo. 



The surface of which that is the equation is the character- 

 istic surface of the series dynamo. 



Dynamo Surface. 



If we impose the condition that n = constant = 1400 



9.8 i 

 1 4- 0.004 i 



See fig. 5, DB. 



(8) E = 



