22 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



ance of this reactor? By what amount can the combined output 

 of the transformers be increased by the addition of this reactor 

 without overloading either transformer? 



95. The following data are given on two transformers which 

 are operating in parallel on both their high- and low-tension 

 sides : 



These transformers are delivering a combined load of 4333 

 kv.-a. at 6600 volts. A reactor of negligible resistance is added 

 in series with one of these transformers on the low-tension side 

 so that they divide this load in proportion to their ratings. As- 

 sume that this does not effect the low-tension voltage. 



(a) What per cent, of its rated capacity is the load on each 

 transformer before the reactor is added? 



(b) What is the ractance of this reactor? By what amount is 

 the total copper loss in the transformers reduced? 



96. Two similar 5-kw. lighting transformers which give a 

 ratio of transformation of 1100:110 volts are connected in series 

 on both the high- and low-tension sides. With both low-tension 

 windings short circuited and with 326 volts impressed on the high- 

 tension windings connected in series the current is 4.55 amperes 

 and the power supplied is 101 watts. On the low-tension side 

 these transformers supply power to a three- wire system. The 

 resistances of the lamp loads on the two sides of the neutral are 

 2.8 ohms and 2.1 ohms. The high-tension line voltage is 2200 

 volts. What is the current in the neutral conductor? What is 

 the voltage across each lamp load? If each lamp takes approxi- 

 mately 50 watts how many should be turned off on one side in 

 order that all of the lamps shall burn with the same brilliancy? 



97. The transformers described in problem 96 are connected 

 in series on both the high- and low-tension sides, and are deliver- 

 ing power to a three-wire circuit on each side of which there are 

 two equal lamp loads taking 32 amperes at 110 volts. 



What is the high-tension line voltage? If one of these loads is 

 short circuited what will be the voltage across the other on the 

 assumption that its resistance and the high-tension line voltage 

 are both unchanged? 



1 Full-load current. 



