246 



METHODS OF CALCULATION 



Similarly, having given the magnetic reluctances sensibly con- 

 stant for the direct flux of the armature and for the transverse flux 

 (excluding the field magnet core), the same diagram may also present 

 to a suitable scale the M.M.F.'s proportional to the flux, multiplied 

 by the reluctance of the armature, of the air-gap, and of the pole 

 pieces respectively. In that case, OA represents the necessary ampere- 

 turns to force the flux through the said reluctances. OB is the part 

 of this M.M.F. furnished by the field magnets; AB the part furnished 



M 



D 



FIG. 5. 



FIG. 6. 



by the armature; BD the supplement necessitated by the stray fields 

 of the armature. 1 DF represents the ampere-turns of distortion 



DF= function of 



Calling K t a coefficient of distortion, or of transverse reaction, anal- 

 ogous to the coefficient K of the direct reaction, and/, (the function) 



1 And eventually by the supplementary stray fields Jf, in the particular case 

 indicated above, where the effect of the stray field from the field magnets is 

 referred to a supplementary term of the armature stray fields. 



