The basic components included in an equivalent circuit of a transformer are: resistances to represent copper losses, inductances for leakage fluxes, an ideal transformer for voltage transformation, and a magnetizing branch for core losses and excitation.

The equivalent circuit acts as a valuable design tool by enabling determination of key parameters like impedance, regulation, efficiency through simulations. It aids optimization of design aspects like core/winding selection based on performance targets.

Referred equivalent circuits facilitate analysis from the perspective of either side by adequately transforming parameters. This enhances flexibility and insights into transformer behaviour from the primary or secondary networks.

The approximate model neglecting magnetizing branch simplifies calculations without compromising accuracy under normal loads. This is because the magnetizing current is negligible compared to load current, improving analytical convenience.

Individual single-phase circuits are first established considering transformer parameters. Then by applying transformations between phase-line quantities per the specific star-delta connection, the final three-phase equivalent circuit model is formulated.