Calculation and Experimental Validation on Leakage Inductance of a Medium Frequency Transformer

Nowadays, medium frequency transformers are widely employed with power electronic converters, offering obvious benefits for modern power system. Rising the switching frequency leads to the need for accurate estimation of the characteristics of a designed transformer. This paper refines the existing analytical frequency-dependent method for accurately calculating leakage inductance in the medium frequency range based on the magnetic field intensity distribution and the stored magnetic energy method. Unlike the previous expressions, the proposed method employs mean turn length of individual layer which makes the calculation more precise. The advantages and impacts of interleaved winding structure to minimize the leakage inductance are also shown by comparing different winding patterns. Transformer prototypes with specifications as 10kW, 500/5000V, 5kHz have been manufactured and tested. The presented equations for inductance calculation are benchmarked to the experimental results on the developed transformer prototypes as well as the finite element analysis (FEM) simulation results.