Three-Phase Transformer Construction and Working Principles

Introduction

Electromagnetic induction: A varying magnetic flux in a loop induces an electromotive force (EMF).
A coil with an alternating EMF system creates a fluctuating magnetic field.
A current-carrying conductor generates a magnetic field.
Alternating current causes a fluctuating magnetic flux in the coil.
Core: Ferromagnetic material links magnetic flux to the secondary winding.
Induced EMF in secondary coils due to electromagnetic induction.
Net EMF in winding is the sum of individual EMFs in each turn.
EMF per turn is the same for both primary and secondary coils.
Voltage transformation depends on the number of turns in primary vs. secondary coils.
Energy conservation: Relationship between primary and secondary currents.

Uses three single-phase transformers with a different coil configuration.
Primary and secondary coils sit concentrically.
Includes two more windings for three-phase power.
Disc-type windings: Used in high power ratings; disc windings connected in series.
Low voltage windings: Delta configuration.
High voltage windings: Star configuration.
Line voltage increases by √3 at the high voltage side.
Outputs: Three phase power wires and one neutral wire.
High voltage insulated bushings: For electrical energy output.

Core: Made of thin insulated steel laminations to reduce eddy current energy loss.
Three-phase limbs created by stacking steel laminations.
Low voltage windings sit near the core.

Energy losses dissipate as heat.
Transformer immersed in cooling oil to dissipate heat through natural convection.
Oil expands with heat absorption; conservator tank accommodates volume change.