THREE-PHASE CURRENT MOTOR. 



79. We found in the second chapter that 



* _ _!_ . b . t . &, 



12 



where b is the width of the motor, and t the pole-pitch. This formula 

 is correct only if the slots in the field and the armature are prac- 



FIG. 22. 



tically closed. As we intend to keep the slots in the field entirely 

 open in order to be able to exchange the coils easily, N will be about 



45 



