57 



coming this resistance, whilst the dynamic 

 characteristic shows the terminal electro- 

 motive force. Thus all the necessary 

 elements exist for determining, by the 

 aid of a diagram similar to Fig. 10, the 

 length of the line O A and its angular 

 position. Having found the point A, the 

 position of the point E' is determined, 

 that is to say, the strength of field O E', 

 which in a motor will allow the prede- 

 termined current to pass. The corre- 

 sponding exciting power is found from 

 the static characteristic, and this gives 

 one point of the motor characteristic. 

 In the same manner other points corre- 

 sponding to different terminal electro- 

 motive forces can be ascertained. The 

 construction is a mere geometrical opera- 

 tion, and need, therefore, not be 

 explained in detail. Fig. 11 shows the 

 relative position of these curves for one 

 of the author's machines, constructed for 

 an output of 60 kilowatts. For the 

 figures from which the diagram has been 

 constructed the author is indebted to Mr. 

 C. E. L. Brown, who has kindly con- 



