12 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



the exciting current with change in the load. Calculate (a) the 

 regulation and (b) the efficiency of this transformer when 400 

 k\v. is supplied to the high-tension winding at 13,200 volts and 

 0.75 power factor. Use the complete transformer diagram in the 

 solution of this problem, (c) Calculate the regulation and effi- 

 ciency of this transformer for the same load on the assumption 

 that the no-load current is negligible and that the core losses are 

 constant. 



53. The following data are given concerning a 1000-kv.-a., 

 66,000 : 6600-volt, 60-cycle transformer: 



Assume that the primary and secondary resistances are equal 

 when reduced to the same side and that the primary and secon- 

 dary leakage reactances are similarly equal. Assume that the 

 magnetizing current varies as the generated voltage and that the 

 core loss varies as the square of this voltage. 



Calculate (a) the regulation and (b) the efficiency when the 

 secondary delivers full-load current at 0.80 power factor and a 

 terminal voltage of 6680 volts, (c) Calculate the regulation and 

 efficiency of this transformer for the same load on the assumption 

 that the no-load current is negligible and that the core losses are 

 constant. 



TRANSFORMER DATA 



54. Calculate (a) the regulation 2 and (b) the efficiency of the 

 transformer No. J for a load of 22 kw. at 0.85 power factor and 

 rated voltage. 



1 Full-load current. 



2 Neglect the exciting current. 



