THE INDUCTION MOTOR. 



voltage necessary to drive this current through the field coils *i 

 motor 7 is proportional to- -- 



99. The magnetizing current of motor //, running at a slip of 2 ~ 

 may be called in, then we have for the magnetizing current of the 

 single-phase motor: 



im =-%- + tn 



For in we have 



in = 0' *'**) ff . 

 hence 



; = - 4- / <r i m a 

 i m (i _|_ <j) = / I +2f 



Im I + 2 ff 



(I3) IT = TT^ 



For <r = o, that is, for a motor without leakage, we have : 



- m -=-L- = 0.500 

 For a = 0.05 we have 



~f- = 0.525 

 Fig. 28 shows the diagram resulting from these considerations. 



O A is the idle current. 



O B is the magnetizing current. 



The point C bisects O A. B' lies upon the semi-circle B B' G, G 

 being the centre of the semi-circle B L, B -=- B L being equal to 

 <r. B' divides the total primary current A' in the ratio of 



OB' I -f- 2 0- 



O A' '' '' 2 + 2C ' 



hence the locus of A' is the semi-circle A A' L. 



55 



