CHAPTER IX 



TRANSFORMER CASES AND TANKS 



ANY one of a variety of materials may be employed in 

 the co ust ruction of transformer cases. The rated output 

 required of the transformer and the appropriate mehod of 

 cooling will usually affect the choice. The principal materials 

 n>ed are cast iron, galvanised sheet iron, sheet steel, and 

 boiler iron. For small sizes of transformers cast iron is 

 generally used, both for air-cooled and oil-cooled designs. 

 'I'll is is for several reasons. The pattern will, for small sizes, 

 not entail large outlay, and this outlay will be spread over a 

 v. i v great number of transformers. Furthermore, the cost of 

 in m castings is small. The labour item in building sheet-iron 

 cases for housing transformers of small capacity renders their 

 cost excessive when compared with cast-iron cases of similar 

 size. Furthermore, the larger the case, the more difficult it is 

 -t, in view of the small thickness of metal. In fact, owing 

 to this difficulty of obtaining a good, sound, thin casting when 

 using cast iron, the walls of the case must be math thicker than 

 would oth. Twise be desirable. For this reason, and because 

 large cast-iron cases are much heavier than either galvanised 

 sheet-iron or boil.-r-inn cases of the same capacity, the cost, 

 \\hni east in>n is u^< d, is nearly or quite as great for large 

 Iran. -formers as for the sheet-iron alternative, lly since 



the necessary patterns are more expensive the larger the case. 

 Sheet-iron cases have also the advantage that a much ui 



bright can hr ein|l..y (1 with a 'jiven thickness of m-tal. \\ith 



cast iron it is not pn .my con>iderahle increase 



1 face for a giv* n thickness of cast iron and for the same 



tlo..r space. In other words, tin- hei^h; ron case 



8.T. I 



