THE TRANSFORMER. 



141 



for its production. The no-load current of a transformer 

 consists, consequently, of two portions, namely, the true 

 magnetising current, which being an idle current lags quarter 

 of a period behind the applied voltage, and the energy current 

 required to overcome the hysteresis and eddy current losses 

 as well as the losses in the primary winding. This current 

 is in phase with the primary voltage. 



As usual, the total current may be obtained graphically 

 from these two component currents, by representing them 

 as two sides of a right-angled triangle, of which the no-load 

 current is the third side. The value of the no-load current 

 may consequently be expressed thus : 



No load current 

 = \/(magnetising current) 2 + (energy current) 2 . 



The composition of the no-load current will be rendered 

 more clear by the following experiment : 



EXPERIMENT XXV. DETERMINATION OF MAGNETISING 

 CURRENT OF A TRANSFORMER AT VARIOUS VOLTAGES. 



DIAGRAM OF CONNECTIONS. 



FIG. 65. 



G Alternator supplying current. 



II Primary and secondary of transformer. 



V Voltmeter. 



A Ammeter. 

 W Wattmeter. 



R Variable resistance for altering voltage at 



transformer terminals. 



C Voltmeter key. 



S Switch. 



