200 ALTERNATING CURRENTS 



In the moderate sizes of transformers, the radiating surface is 

 increased by corrugating the case (Fig. 187). As transformers 

 increase in capacity, it becomes difficult to dissipate the heat by 

 means of the surface of the case alone. One method of increasing 

 t ho radiating surface is to use exterior tubes running from the top 



FIG. 188. Westinghouse 1000-kv-a., 3-phase, 60-cycle, 46,000-23,000-volt 

 tubular-tank transformer. 



of the case to the bottom (Fig. 188). The hot oil passes out 

 from the tank into the top of the tubes, is gradually cooled and 

 descends through the tubes to the bottom of the tank where it 

 again passes up through the windings and core. 



jPEKTY OF ELECTRICAL '.', | 



FACULTY OF APPLIED SCIENCE. 



