200 ELEMENTS OF ELECTRICAL ENGINEERING. 



are placed side by side with a thin sheet of insulating material 

 between them, as shown in Fig. 167, they are connected together as 

 a single coil or section leaving both the terminals on the outer rim, 

 and wound with tape as shown in Fig. 168. A number of such 

 sections are placed side by side, primary and secondary sections 

 alternating,* with intervening spaces for the circulation of oil or 

 air for cooling, and the whole is bound together as shown in Fig. 

 169. This complete coil structure is then mounted on a base and 

 the laminations are built up around each leg, as shown in Fig. 

 I/O, the inner edges of the laminations being separated from the 



Fig. 170. 



coil structure by vertical strips of very tough insulating material, 

 and spaces being left between the laminations at intervals, as 

 shown, for the circulation of oil or air. 



Figure 1 7 1 shows a large shell-type transformer of the Westing- 



* This detail of construction has for its object the reduction of magnetic leakage as 

 explained in chapter XI. 



