Kinsley — Discussion of Series Dynamo-Electric Machines. Ill 



can be expressed by means of the empirical equation given on 

 page 111 eq. (2). This is justified by the experimental work 

 given in II. It will be found to be true in all the many 

 cases where the demagnetizing effect of the armature remains 

 nearly constant or relatively small. This condition is found 

 when the brushes remain stationary and the change in arma- 

 ture current changes but slightly the resultant field. 



The data mven first were gotten from a machine which had 

 an exceedingly strong field. Machines with relatively weaker 

 fields have the constants a and b (p. Ill) apply to only 

 small parts of the characteristic, see p. 127. 



The dynamo and motor can be considered together since in 

 the case of the dynamo 



e = E — ri 

 and for the motor 



e = E, + ri 



the surface in which only the total induced electromotive 

 forces are considered being similar in all respects. 



Assume for the present that the following equations are 

 true. 



(1; E = 4AnjH 



From (2) it is seen that an increase of the magnetizing 

 ampere turns will decrease the permeability of the circuit. 



from (2) and (1) 

 (3) E=4Af^GSi^^. 



frOm our assumptions we can let 



4AGS/i, , , 



— _- = a constant = a 

 bO 



also 



Sff = a constant = b 



