Accurate Evaluation of Leakage Inductance in High-Frequency Transformers Using an Improved Frequency-Dependent Expression

Moving toward higher power density in magnetic components, which is often realized by increasing the operating frequency, leads to the need for development of more accurate design tools, for example, more accurate expressions for core losses, winding losses, and leakage inductance calculations. This paper presents a new analytical expression intended to accurately evaluate the leakage inductance of transformers in the high-frequency range in which the behavior of the magnetic field within the windings is altered. Unlike conventional expressions, which usually overestimate the leakage inductance at higher frequencies, this expression accounts for high-frequency behavior of the magnetic field and provides high accuracy when operating at high frequencies. These high accuracy and applicability makes the derived expression of interest for designers to avoid time consuming finite-element simulations without compromising with accuracy. The expression is validated by 2-D finite-element method simulation, as well as by measurements.