160 



THE TRANSFORMER. 



In order to make a complete test of a transformer on induc- 

 tive or capacity load, the method just described must be 

 extended by measuring the output as well as the input by 

 means of a wattmeter. In order to determine the power- 

 factor of both circuits and the ratio of transformation an 

 ammeter and voltmeter should still be put in both circuits. 



EXPERIMENT XXX. DETERMINATION OF EFFICIENCY OF 

 A TRANSFORMER ON INDUCTIVE LOAD. 



DIAGRAM OF CONNECTIONS. 



M2 Sl 



FIG. 74. 



and secondary 

 for reading primary and secondary 



M lt M 2 Source of alternating current. 

 /, //. Primary and secondary windings of transformer. 

 R Variable resistance composed of inductive and 



non-inductive resistances. 

 V l} F 2 Voltmeters for reading primary 



voltage. 

 A lt A. 2 Ammeters 



current. 

 W lt Wz Wattmeters for reading primary and secondary 



power. 



C Voltmeter switch or plug. 



$!, 2 Switches for breaking primary and secondary 



circuit. 



The method of carrying out this experiment is practically 

 identical with that given for the preceding test, except that 

 the secondary wattmeter must be read and the power-factor 

 for the secondary circuit calculated. It is usually not 

 possible in practice to obtain .complete curves of efficiency 

 and ratio of transformation at different power-factors, but 

 isolated points are obtained at such power-factors as are 

 required, and the curve can then be drawn in the neighbour 

 hood of these points by comparison with the complete curve 

 already taken on non-inductive load. 



