Improved Computation of Core Inductance for Fast Transient Analysis of Transformers

This letter introduces a simple and accurate formula for the computation of the inductance component due to the flux inside the transformer core for fast transient analysis. When compared with an existing formula, the new formula yields considerably better behavior for a broad frequency range (1 Hz to 10 MHz). In addition, two finite-element method approaches for core inductance computation at different frequencies are evaluated and compared: flux linkage and method of energy. It is demonstrated that these methods can provide substantially different results at high frequencies.