248 



ELEMENTS OF ELECTRICAL ENGINEERING. 



secondary coil, N f the number of turns of wire in the primary 

 coil, N" the number of turns of wire in the secondary coil, R 

 the resistance of the secondary receiving circuit, X the react- 

 ance of the secondary receiving circuit, and g l b l is the circuit in 

 which the magnetizing current M may be thought of as flowing, 

 gf being the power component of M y and b^E' being the 

 wattless component of M. (See Art. 115). 



When R' and coP are small, the loss of voltage in R f and 



Supply main 



Supply main 



Combination of simple circuits which is approximately equivalent to Fig. 213. 

 Magnetizing current assumed to be constant. 



Fig. 216. 



(0P, Fig. 215, is negligible, and the voltage across the circuit 

 g l b l is sensibly equal to the supply voltage, whatever the load on 

 the transformer may be, so that, the supply voltage being con- 

 stant, the magnetizing current M is sensibly the same in value 

 at all loads. In this case the combination shown in Fig. 216 

 reproduces the conditions of Fig. 2 1 3 with sufficient accuracy for 

 most practical purposes, and in fact nearly all practical calcula- 

 tions of transformers and induction motors are based on Fig. 216. 



121. The circle diagram of the transformer when the secondary 

 receiving circuit is non-inductive. It was shown in Art. 38 that 

 the locus of the current produced by a constant voltage in a cir- 

 cuit of constant reactance and variable resistance is a circle of 

 which the diameter is at right angles to (and 90 behind) the 

 voltage. To vary the resistance R of the secondary receiving 



