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ELECTRICAL MACHINERY 



70. Construction. In actual construction the trans- 

 former does not resemble at all that given in Fig. 168. 

 The cores can be most economically built up of rectangular, 

 instead of circular, sheets, and the two coils are always 

 placed as closely together as possible. 



Two General Types. Two types of transformers have 

 been developed in which both of these ideas are incor- 

 porated; they are the core type and the shell type. In 

 both these types the cores are built up of thin sheets of iron, 



generally rectangular in 

 shape, and the primary and 

 secondary coils are placed 

 in very intimate relation 

 with one another. 



Core Type. The core type 

 closely resembles the ele- 

 mentary transformer shown 

 in Fig. 168; however the 

 shape of the core is rectangu- 

 lar (its cross-section is nearly 

 square) and the two coils 

 are placed one over the other 

 as close together as possible. 

 Each coil is divided into two 

 sections, the two sections 

 being placed on opposite legs 

 of the core. Fig. 171 shows 



a view of an assembled core-type transformer ready to be 

 placed in its containing case. Space is left between the 

 two coils so that oil for cooling purposes may circulate 

 through the windings. 



Shell Type. The shell-type transformer is shown in 

 Fig. 172. The coils of the core type are generally cylin- 

 drical in form but in the shell type they form a rectangular 

 structure (as shown in Fig. 173) similar in form to the core 

 of the core type, and the laminations (sheets of which the 



FIG. 171 . Small Core-type Trans- 

 former, Completely Assembled. 

 General Electric Co. 



