THE TRANSFORMER. 



169 



EXPERIMENT XXXI. DETERMINATION OF EFFICIENCY OF 

 A TRANSFORMFR BY SPLIT DYNAMOMETER. 



DIAGRAM OF CONNECTIONS. 



^* vAAAM, 



FIG. 80. 



M l M 

 I, II. 

 D 



R 



V V 



r i r s 



s,, s., 



Source of alternating current. 



Primary and secondary of transformer. 



Split dynamometer. 



Ammeters or dynamometers reading primary and 



secondary currents. 



Non-inductive variable load resistance. 

 Voltmeters reading primary and secondary voltage.* 

 Switches. 



Instructions. Connect the primary of the transformer 

 to be tested to a suitable source of alternating voltage in 

 series with an ammeter and one coil of the split dynamometer. 

 (It is preferable to put the swinging coil in the high tension 

 side.) Connect the secondary of the transformer to a variable 

 non-inductive load resistance in series with a second 

 ammeter and switch. Throughout the experiment maintain 

 the primary voltage constant. 



Commencing with small values of the secondary current, 

 gradually increase the load to the maximum value desired, 

 and for each value of the current take readings on the two 

 ammeters, the dynamometer, and the voltmeters. The no- 

 load losses can obviously not be measured by this method, 

 since the dynamometer will give no deflection without the 

 secondary current. 



While still hot, measure the resistance of primary and 

 secondary windings by sending a direct current through 



* In the diagram only a single voltmeter is shown connected to the 

 secondary of the transformer, the primary voltage being assumed to be 

 measured and kept constant at the supply mains. 



