ANALYSIS OF ARMATURE REACTANCE 



'59 



displaced through this distance. Potier * found experimentally that 

 such is the case. 



If I be taken to represent the constant wattless current correspond- 

 ing to the curve LP', then we may write 



and 



PR = E.I 

 EF = A r l 



(1) 

 (2) 



where E, and A r are two constants.f In order to find the values of 

 these constants, we determine the curve LP' J for any convenient value 



E XCITIN & 



R. R. E N T 



FIG. 117. Analysis of Armature Reactance into Two Components. 



of I, and, having made a tracing of LP' and the axis of exciting current, 

 and marked the position of a convenient point P' on LP', we dis- 

 place the tracing, keeping the axis of exciting current parallel to its 

 original direction, until a position is found in which the tracing of 

 LP' exactly fits over OP. We then prick the position of P' through 

 the tracing, thus obtaining the corresponding position of P on OP. 

 Through P and F lines are drawn parallel to the two axes, and the 

 lengths PR and P'R thus obtained enable us, by using equations (1) 

 and (2), to find E; and A r . 



* Edairage tilectrique, vol. xxiv. p. 133 (1900). 



t E, = reactance corresponding to leakage self-inductance, A = armature reaction 

 constant. 



J LP' is frequently termed the load charaeteri$tie corresponding to a given armature 

 current and power factor. 



