Equivalent Circuit of Transformer
An equivalent circuit model translates the physical complexities of a real-world transformer into standard electrical components (inductors, capacitors, and resistors).
Resistance – Rdc and Rac
Winding resistances depend on frequency due to skin and proximity effects, especially near core gaps, where fringing, non-uniform B-fields cause severe localized current crowding.
Inductance – leakage and magnetizing
Magnetizing inductance – A fundamental characteristic, rather than a parasitic. It is the inductance required to establish magnetic flux within the core, determined by the primary turns and core material properties. Its effective value is dynamic, varying with operating frequency and current magnitude (dropping significantly as the core nears saturation).
Leakage Inductance – A parasitic series inductance caused by magnetic flux that leaks into the surrounding air instead of linking the primary and secondary windings. Its value is primarily dictated by the physical arrangement and interleaving of the windings.
Capacitance Matrix and Inter-winding Capacitance
Inter-winding capacitance between the primary and secondary, dictated by the winding arrangement and the dielectric materials of the isolation barrier.
Intra-winding Self Capacitance
Primary and secondary parasitic capacitances are formed between turns and layers. They remain largely constant across a wide frequency range and depend on the winding geometry and surrounding dielectrics.
