342 



PRINCIPLES OF ELECTRICAL DESIGN 



mation to this ideal m.m.f. distribution would be the arrange- 

 ment shown by the stepped curve, with 9,000 ampere-conductors 

 in each slot. This would produce a flat-topped flux-distribution 

 curve, a condition which might be remedied by putting 5,000 

 ampere-turns in the empty slots at the center of the pole face; 



22.5 



45 



67.5 .90 

 Electrical Degrees 



FIG. 140. Ideal flux-distribution and m.m.f. curves 8000 k.v.a. 

 turbo-alternator. 



but such a procedure would be very uneconomical and unsatis- 

 factory. The best thing to do will be to increase the permeance 

 of the center tooth, either by reducing the width of the two slots 

 on each side of the center tooth, or by partly filling up these 

 slots with iron wedges so shaped as to produce the effect of a 

 tooth with parallel sides. These slots should, in any case, be 



