TRANSFORMERS 



437 



below a certain point, the circuit is broken by the action of a 

 spring, and the lamp goes out. It may also be obtained with an 

 indicator for use on open-circuit signal systems, in which case the 

 signal circuit is closed when the water flow is interrupted. 



With the shell-type construction the core iron is assembled 



FIG. 275. Core for 4000 Kv.A. Core-type Transformer. 



around the coils (Fig. 274), and follows the coil assembly instead 

 of preceding it as in core-type construction. The cores for the 

 latter are two-legged for single-phase (Fig. 275) and three-legged 

 for three-phase units. They are built up from sheet laminations 

 of high-grade non-aging silicon steel, clamped at top and bottom 



