Admittance and Impedance Loci. 307 



The semicircle JK H is the locus for the primary electro- 

 motive force in the .absence of magnetic leakage. The semi- 

 circle JK'N is the locus for the primary electromotive force 



Fig. 7.— Effect of Magnetic Leakage. 

 Ko_ 



OPEN CIRCUIT 



when the coefficient of magnetic leakage f is constant from 

 open circuit to short circuit. In this case we have the 

 relations 



JK'_JN M 2 _ 



JKo-JH-LjL,, - ^ g ; 



In an actual transformer the magnetic leakage is not con- 

 stant, but varies with the load. The locus represented by the 

 dotted curve JK"N is for such a case in which the magnetic 

 leakage is zero on open circuit and increases to the maximum 

 at short circuit. Where the magnetic leakage is variable, it 

 is determined for any point as K" by the ratio of JK" to JK . 



?=1 



/ JK" 



Thus let us suppose that the back electromotive force JK", 

 actually induced in the primary by the secondary current I 2 , 

 is eighty-one volts ; and that JK , which would be the back 

 electromotive force in the absence of magnetic leakage, is 

 100 volts. We then have the equation 



^=Vm-To=^ 



Z2 



