152 



PRINCIPLES OF ELECTRICAL DESIGN 



equal amount of flux, but of opposite sign, must enter the arma- 

 ture from the leading pole tip or interpole, and this component 

 of the compensating flux will actually be cut by the conductors 

 in the slot, thus neutralizing the e.m.f. developed by the cutting 

 of the end fluxes. This will be made clearer by reference to Fig. 

 59, which is generally similar to Fig. 54, except that, instead of 



1 1 1 ijj-in 

 W 



FIG. 59. Diagram showing component fluxes cut by coil during 

 commutation. 



the actual interpolar flux, two distinct curves have been drawn, 

 the one, F, representing flux distribution over armature peri- 

 phery due to the field coils acting alone, and the other, Z, repre- 

 senting the flux distribution due to the armature windings acting 

 alone. The addition of these two fluxes at every point will not 

 always reproduce the actual flux curve of Fig. 54, because of 

 possible saturation of portions of the iron circuit such as the 

 armature teeth and pole tips; but, in the commutating zone, the 

 method of adding the several imaginary components of the 



