ALTERNATING-CURRENT TRANSFORMER. 



that it seems peculiar that it has taken such a long time to arrive at 

 this solution. 



That the locus of the vector of the primary m. m. f. must be a 

 semi-circle, follows directly from the diagram of Fig. 41. This circle 

 is reproduced in Fig. 46. The thick lines show the triangle of the 

 magnetomotive forces. 



152. O C is the magnetizing current. If the transformer runs on 

 open-circuit, O C becomes equal to O K. We see, therefore, that the 



20 40 60 80 1OO VOLTS 



Fig. 46. 



magnetizing current is not constant for all loads, but decreases with 

 the diminution of the secondary resistance. W hat remains constant is 

 the primary magnetic field Fi, which is composed of the common field 

 F and the leakage-field ft, F is constantly diminishing, while ft is 

 increasing, their vector-sum being constant. 



153. K divides O~D in a constant ratio, O~K = v , . O~D. Hence, 

 drawing a line through K, for instance, A K, and producing it until it 



83 



