125 / 2021-06-21 14:09:09

frequency-dependent leakage inductance model for high-frequency transformers considering faraday shields

The frequency-dependent leakage inductance of high-frequency transformers is critical for power electronic transformers' transmission capacity and efficiency [1], [2]. The accurate model of leakage inductance significantly influences the design of high-frequency transformer, which usually utilizes the leakage inductance to achieve soft switch or takes it as the resonant element in power conversion circuits [3]. The Faraday shields are widely used in high-frequency transformers to restrain common-mode interference, which conducts the high-frequency displacement currents between the primary and secondary windings to the ground [4]. The Faraday shields are usually placed between the primary and secondary windings where the magnetomotive force (MMF) is pretty high. Severe eddy currents are induced in the Faraday shields and contribute to the notable descent of leakage inductance with the increase of frequency. In this article, the frequency-dependent leakage inductance model for foil winding high-frequency transformers considering foil Faraday shields is established, and the closed-form formula of it is derived. Then, the equivalent method of transforming the rectangle, round, round Litz and rectangle Litz wires into the foil wire is given. The corresponding formulas are given as well. The established model is verified by the experiment method and finite element method in five case studies. The primary error source of the model is analyzed further and further work is discussed finally.

Keywords: power electronic transformer; high-frequency transformer; frequency-dependent leakage inductance; faraday shield.