V.  Effect  of  Saturation  on  Magnetic  Distribution 

46.  The  preceding  discussion  of  Figs.  92  to  95  omits  the  effect 
of  saturation.  That  is,  the  assumption  is  made  that  the  mag- 
netic materials  near  the  air  gap,  as  pole  face  and  armature  teeth, 
are  so  far  below  saturation  that  at  the  demagnetized  pole  corner 
the  magnetic  density  decreases,  at  the  strengthened  pole  corner 
increases,  proportionally  to  the  m.m.f. 

The  distribution  of  m.m.f.  obviously  is  not  affected  by  satu- 
ration, but  the  distribution  of  magnetic  flux  is  greatly  changed 
thereby.  To  investigate  the  effect  of  saturation,  in  Figs.  96  to 
99  the  assumption  has  been  made  that  the  air  gap  is  reduced  to 
one-half  its  previous  value,  la  =  0.5,  thus  consuming  only  one- 
half  as  many  ampere-turns,  and  the  other  half  of  the  ampere- 
turns  are  consumed  by  saturation  of  the  armature  teeth.  The 
length  of  armature  teeth  is  assumed  as  3.2,  and  the  space  filled 
by  the  teeth  is  assumed  as  consisting  of  one-third  of  iron  and 
two-thirds  of  non-magnetic  material  (armature  slots,  ventilating 
ducts,  insulation  between  laminations,  etc.).