THE TK. \\-SI-nKMEK 



197 



poor regulation. By having both a primary and a secondary on 

 each leg. as shown in Fig. 183 (a) and Fig. 183 (c), the leakage flux 

 is reduced to a very small value. If the high-voltage winding 

 placed next the core, it would be necessary to insulate it, 

 both from the core and from the low- volt age winding. Thus two 

 layers of high-voltaic insulation would be necessary. By placing 

 the high-voltage winding outside, and around the low-voltage 

 winding, only the one layer of high- voltage insulation, that be- 

 tween the high- and low-voltage windings, is necessary. 



In the core type of transformer the mean length of turn is less, 

 but the mean length of magnetic 

 path is greater than it is in the 

 shell typo. The core type of trans- 

 former is well adapted to high volt- 

 ages, especially in the smaller 

 capacities, because the insulation 

 problem is not difficult. 



(a). ArniMirrriiciil <>f <'oih :iricl ''ore 

 in sh<'ll-t> ; incr. 



Coil and core assembly of 

 Wanner shell-type dist rilmtion trans- 

 former. 

 IK,. L84. Shcll-tyi mer. 



In the shell type of i ransfnrmer, the iron surrounds the copper, 

 as shown in Fig. 1M. The core ha- the form of a figures. The 

 entire tln\ ' h rough the central part of I he core, but outside 



-ntral core it divides, half goini; in each direction as shown 

 n. 184 (a). Thi- n-iilis in a much shorter effect ive length 

 of maiiiietic path, but -r mean length of turn. The coils 



are made in the shape of pancakes, usually wound with strip 

 copper. The-.- roil- an- taped, and the primary and s< condary 

 are usually stacked SO that each primary i- adjacent to a Sec- 

 ondary. In \\\\< mannei- the leakage ilux of both primary and 

 secondan iced to a very small value. In I 



prim:! the hiuh -ide and the secondaries are the IMU 



