

166 



PRINCIPLES OF ELECTRICAL DESIGN 



between the armature surface and neighboring masses of iron. 

 It can be predetermined within reasonably close limits by plot- 

 ting the full-load flux curve, C, as indicated in Art. 43, Chap. 

 VII. The flux entering and leaving the surface of the armature 

 in the commutating zone, when the axial length l p of the interpole 

 is appreciably less than the gross length l a of the armature core, 

 is indicated in Fig. 63. Before calculating the flux which must 

 enter the armature teeth from the commutating pole, it will 

 be advisable to define clearly the various flux components to be 

 considered. 



FIG. 63. Commutating pole : showing direction of flux at armature surface. 



Many of the symbols used in the previous calculations will be 

 employed, but it is proposed to alter the meaning of some of 

 these because it will be more convenient to think of the slot 

 flux per centimeter length of slot instead of the flux over the 

 whole length of slot as in the previously developed formulas. 

 This slight change will probably lead to less confusion than if 

 a complete new set of symbols were to be introduced here. 



& c = total flux entering armature teeth from interpole, over 



area of width W a and length l p . 

 $ e = total end flux (one end of armature). 

 4> = total slot flux per centimeter of armature length (two 



slots). 

 $ e = equivalent slot flux per centimeter, if magnetic lines 



pass outward from armature core through root of teeth 



(two slots). 

 $'e = equivalent slot flux per centimeter, if magnetic lines pass 



inward from air gap through top of teeth (two slots). 



