FORCED-COOLED TRANSFORM! 169 



the cast-iron ba>e are indicated in various of the 

 illustrated in this dun 



-pi nil cooling-coil for the circulating water should be of 

 .:li a view to ensuring a minimum of corrosion. Bras. 

 pipes f.>r tin- purpose may be thinner than iron pipes, and also, 

 .' the heat conductivity of brass is greater than that of iron, 

 th- It. at is more effectively abstracted from the transformer by 

 way of the oil, the brass pipes, and, finally, the circulating water. 

 In the bulletins of a transformer-manufacturing firm of wi.b 

 rience, the amount of ciivulatinu r water required at full load 

 a temperature of 15) is given as approximately 



0,8 gallon per minute for 500-kw transformers 

 1,1 1000-kw 



' 1,5 M M '2000-k\v 



A thermometer is often provided, which extends through the 



. and by means of which the. attendant can intelligently 



control the amount of water supplied. It would be absolutely 



us to reduce the oil temperature below the 



temperature of the room, a-- this would cause the transformer 



at." 



It will be of interest to indicate the method of making 



MILT calculation- jor a fore, d-u ater-cooled oil-t raiislormer. 1 



Dfl take ftfl ;ni instance a KKK)-kw .".0-cycle transformer. 



lofifl is 7 kw and the 7 2 7^ loss at rat. d lad is also 



/1000 X 100 \ 



-e,|Uelitly the full-load -\\\, -j, H.'V is ^ -- j0jj - =j 



cent. To maintain a constant t. -mp.-rat ur- 



must be trunsfrrred h,.m the oil in the case to the water inside 



ooling pipes at the rate of 1 | kw. Thus in each hour 



the \\-jit.-r must cany away 1 ! of energy. 1,10 kelvin 



t.-mp.-rature of 1 ton of water by 1. If it is 



. 



author's " Heavy El 



