THE INDUCTION MOTOR. 



Hence the locus of A is an arc the chord of which is determined by 

 the ratio. 



O~K 



(5). 



Vi ^ KL 



157. The centre of this arc is determined by the angle Os K L, which 

 is equal to Q O P, the angle of lag in the secondary. Angle Oi O K is 

 equal to Q O P. 



CAPACITY IN THE SECONDARY. 



158. Fig. 48 is constructed for a capacity in the secondary in series 

 with the resistance. Angle P O B is the secondary lead, Ft is the 

 secondary field, triangle O A K is the triangle of the m. m. ff. We 

 find exactly as before : 



OK l 



= a = i 



O L 



Bearing in mind that angle O G K is constant and equal to angle 

 N O P, it follows at once that the locus of G and that of A are circles. 



159. Again angle 3 K L is equal to angle Oi O K, equal to angle 

 P Q, the angle of the secondary lead. 



HYSTERESIS AND EDDY CURRENTS. 



160. A word about the way in which hysteresis and eddy currents 

 should be taken into account. Assuming them to be constant for all 

 loads which they are not, as, if the leakage-path is slightly saturated, 

 the leakage-flux becomes greater with larger currents, and the greater 

 loss in the leakage-path may outdo the decrease of the loss in the main 

 field it seems most logical to take these losses into account by as- 

 suming a lag between the common field O C and the magnetizing cur- 

 rent. This lag diminishes the secondary current. Draw a line par- 

 allel with L D, the distance of which from L D being equal to the loss 

 in watts through hysteresis and eddies divided by the primary volt- 

 age, then the secondary currents mus* be measured between this line 

 and the semi-circle O*. 



86 



