THE INDUCTION MOTOR. 



duced by the same field upon a coil which is not distributed, but 

 lodged in only one groove. The latter, case is represented in Fig. 9. 

 It may not be amiss to call attention to the fact that a coil like that in 

 Fig. 9 would produce a rectangular magnetic field twice as large as 

 that shown in the figure. Hence the inductance of the flat coil is 

 one-third as large as the inductance of the coil lodged in one slot. 



20. The e. m. f. generated by the field in Fig. 7 can now easily be 

 calculated. 



The number of lines of induction represented by the white area in 

 Fig. 7 is equal to 



The e. m. f. produced by this flux is 



<?, = 2.22 . ~ . z . ( -5. . . t . b . (&\ io* 



V 4 3 / 



The hatched areas represent a flux equal to 



*""**- 



6 2 



The e. m. f. produced by this flux is 



e u = 2.22 . ~ . z . -|- (i . / . * . (B) 10-8 

 Hence 



* = e l + ^n = 2.22 . ~ . z . ( p .t.b.Qt] lO' 8 

 The total flux amounts to 



<t> = -3- . b . t . (B, hence 



12 



6 = 2.22 . ~ . Z . . $ . 10-8 

 21 



(5) e = 2.12 . ~ . z . $ . io' 8 volts. 



21. The ampere-turns in each phase which are needed to produce 

 the induction (B in the air-gap are determined by the consideration, 

 which follows immediately from Fig. 7, that 



2 (o . 4 JT . . / . 1/2. ) = (B 2 A 



