THE ARMATURE REACTIONS OF ALTERNATORS 255 



Thus the coefficients K and K t are obtained simply by taking 

 of the mean ordinates. For two-phase currents, one would similarly 

 take |, that is to say, unity. 



If instead of one slot per phase, there were several, n for example, 

 the mean ordinate would be first divided by n. 



In this manner, the following figures would be obtained: 



TABLE IV 



EMPIRICAL COEFFICIENTS 

 Three-phase winding, with three separate coils per pair of poles. 



In practice an alternator is rarely found where the flux occupies 

 less than two-thirds of the pitch, and besides in this case a winding of 

 twelve bobbins with six short slots should be taken, in my opinion, 

 instead of the ordinary winding, as will be mentioned further on. 



The coefficients of self-induction / and /', corresponding to the 

 two reactions, are deduced from the values of K and K t by evaluating 

 the corresponding fluxes and the E.M.F.'s which they induce in the 

 windings themselves by means of the ordinary formulas. From this, 

 calling k the winding factor, the mean value of / which takes account 

 of the reduction, by distribution of the wires, in the E.M.F. pro- 

 duced in the winding by a sinusoidal flux, 1 



1= 



qRt 



qRd 



1 See in particular the coefficients in my above-mentioned analysis of the 

 rotating magnetic fields, Eclaimge Electrique, 1895. 



