22 



The following table gives the value for 

 k for different cases, all referring to poles 

 of rectangular shape and coils in which 

 the active wires are straight : — 



1. Width of poles equal to pitch, ) 

 toothed armature and winding > k = 2.000 

 concentrated in the recesses . . ) 



2. Width of poles equal to pitch, ) 



smooth armature and winding yk = 1.160 

 spread over the whole surface . ) 



3. Width of poles equ:il to pitch, "| 



smooth armature and winding [k =. 1.686 

 covering only one-half the sur- f 

 face j 



4. Width of poles equal to half the I 



pitch, smooth armature and \k = 1.688 

 winding spread over the whole [ 

 surface J 



5. Width of poles equal to half the ] 



pitch, smooth armature and I k = 2.300 

 winding covering only one-half j 

 the surface J 



6. Width of poles equal to one-third 1 



the pitch, smooth armature and | k = 2.830 

 winding covering only one-third f 

 of the surface J 



According to the ordinary sine-formula 

 the coefficient is k = 2.220; and this 

 agrees fairly well with case 5, which is 

 the most frequently met with in actual 

 practice. The formula for e presupposes 



