5-A] 



STUDY AND OPERATION. 



139 



loading method is not so good for the accurate determination of 

 efficiency and regulation. These can be computed much more 



Open-circuit Vottag* 



5 10 15 20 



SECONDARY CURRENT; AMPERES 



FIG. 4. Curves for 2,000/100 volt, 2 K.W. transformer ; see also Fig. 8, Exp. 5-6. 



accurately from the losses, determined without loading, as in 

 Exp. 5-B. 



21. Load the transformer with an inductive load and take 

 one reading of the instruments. It will be seen that the sec- 

 ondary voltage is somewhat less than it was with non-inductive 

 load that is, the regulation is poorer.* This happens when 

 induction motors are operated from transformers. In this case 

 the secondary current is lagging. If the secondary current were 

 leading, the secondary voltage in some cases would increase, 

 instead of decrease, with the load. The results are similar to 

 those obtained for an alternator ; see Exp. 3~B, particularly Fig. 7. 



22. Design Data and Computation of Flux Density. Note 

 the construction and essential dimensions of the transformer, 



* (2ia). If the leakage reactance of a transformer is small, compared 

 with its resistance, the regulation may be better at low than at high power 

 factor; compare 28, Exp. 3-6. 



