20 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



rated full-load current, the first at unit power factor and the sec- 

 ond at 0.88 power factor. If the low-tension circuits are now 

 connected in parallel what is the current in each transformer? 

 Compare these currents with their full-load values. 



Assume that the currents taken by the low-tension circuits and 

 the power factors at which they operate remain unchanged. 



89. Two 50-kw. transformers are connected in parallel on 

 both the high- and low-tension sides. Their constants are given 

 in the following table: 



They are alike except for the difference in their ratios of trans- 

 formation. These transformers supply a combined load of 93 

 kw. at 0.89 power factor on the low-tension side at a terminal 

 voltage of 2300 volts. What is the current in each transformer? 



90. The following data are given on two transformers which 

 are operating with both their high- and low-tension windings 

 in parallel : 



The ratios of transformation are slightly different. These trans- 

 formers take a combined power of 460 kw. at 0.90 power factor 

 from an 11,000-volt circuit. 



(a) What is the current in each transformer? 



(b) If the ratios of transformation are made equal by the 

 removal of a few turns from the high-tension winding of the 500- 

 kw. transformer, what is the current taken by each transformer 

 for this load? Assume that the short circuit data would be 

 unchanged. 



91. The following data are given on two transformers which 

 are operating in parallel on both the high- and low-tension sides : 



1 Full-load current at rated voltages. 



