Single phase transformers models are generally constructed by treating the transformer as a 4-terminal network, and determining the relevant parameters by open-circuit and short-circuit tests/analysis. A general understanding of transformer construction and operation being used to influence the classical model, and give its components some physical significance, with names such as leakage inductance and turns ratio etc. However, apart from an understanding of the relationship between core flux and voltage/turn, the transformer is still essentially considered as a black box. This thesis aims to develop a better understanding of the internal operation of transformers, particularly in regard to the establishment of core flux and power flow.
The magnetic flux is initially established on the surface of the core before diffusing into the interior of the core/laminations, while the power is transferred from the primary to the secondary, by the E and H fields in the transformer window space, between the primary and secondary windings. The process of establishing flux on the surface of magnetic cores is the same as that involved in establishing current on the surface of conductors. It involves transmission line type electromagnetic wave propagation and reflections to build up the current/flux on the surface of the conductor/core followed by the relatively slow diffusion into the interior of the conductor/core.
These electromagnetic processes are fundamental to everyday electrical engineering and are worthy of understanding, at least at a conceptual level.