250 ELEMENTS OF ELECTRICAL ENGINEERING. 



voltage E r of given value, and it is required to calculate the 

 secondary terminal voltage when the transformer delivers current 

 to a receiving circuit of given reactance X and given resistance 

 R. The effect of magnetizing current is entirely negligible, and 

 to base the solution of this problem on Fig. 216 rather than upon 

 Fig. 2 1 5 is merely to neglect the effect of magnetizing current. 



Solution. Calculate /' by dividing E r by the impedance 

 of the main circuit in Fig. 2 1 6, remembering of course that the 

 total resistance of the circuit is R' + (N'/N") 2 R" + (N'jN'JR, 

 and that the total reactance of the circuit is &P -f (N f JN'^X. 

 Having thus found the value of /', calculate the reactance 

 voltage I'(N'IN"fX and the resistance voltage I'(N' JN'JR. 

 The square root of the sum of the squares of these two voltages 

 multiplied by N' f jN f is the required secondary terminal voltage. 



If the transformer load is reduced to zero the secondary tei- 

 minal voltage rises to the ideal value (= E r N" jN f ), and, by 

 expressing the increase of secondary terminal voltage in per cent, 

 of the value of the secondary terminal voltage under load, we have 

 the regulation in per cent. 



