Page 539 - Basic Electrical Engineering

Figure 6.5 Core-type and shell-type transformers

The choice of type of core to be used for transformer construction depends
on a number of factors. In power transformers, in general, the core-type

construction is preferred while for distribution transformers, the shell-type
construction is preferred. The leakage flux and leakage reactance of a

transformer depends upon the magnetic coupling between the primary and
secondary windings. Voltage regulation and short-circuit impedance depend
upon the leakage reactance of a transformer. In the shell-type construction the

magnetic coupling is better than in the core-type construction.