An Experimental Comparison of the Effects of Nanocrystalline Core Geometry on the Performance and Dispersion Inductance of the MFTs Applied in DC-DC Converters

Abstract

The development of Medium Frequency Transformers (MFTs) from a novel perspective is essential for the advancement of today´s various relevant applications such as the emerging solid-state transformers, along with interfaces for the interconnection of photovoltaic parks and electric vehicles. The analysis, design and implementation of MFTs pursuing the achievement of characteristics such as high power density, high efficiency, and a specific dispersion inductance is a key goal for designers. There are several parameters and design methods that influence the final performance of an MFT, such as the geometry and material of the core. The advantages/disadvantages of each material/geometry combination, about the dispersion inductance for instance, are not well known, even considering a single material but various geometries. This paper presents the analysis, design and experimental development of three nanocrystalline-core MFTs, each one with a different core geometry (toroidal, type CC and shell-type). The purpose of this work is to evaluate and compare the most favourable characteristics and performance of each type of geometry, tested at 5 kHz and 1.75 kVA. The cases studied, in simulation and experimentation with scaled prototypes, focus on evaluating the power density, the core losses, the winding losses, the geometric dimensions, and the dispersion inductance obtained in each MFT, as well as its performances operating with sinusoidal and square waveforms. The results show that: 1) the toroid core has higher efficiency; 2) the shell core has the lowest dispersion inductance and is easier to build, and 3) the CC type has the highest dispersion inductance. This new information is a step to further understand how to get more controllable, more efficient MFTS, with a higher power density and lower cost, depending on the intended application of cutting-edge DC-DC DAB-type converters.

Power Losses Models for Magnetic Cores: A Review

“…It is worth to mention, that there are some intermediate steps, which are related to core physical and magnetic parameters such as the cross section of the core, section of the core, length of it, effective relative permeability, peak to peak density ripple, among others [ 141 ]. In the same way, choosing a gapped core (a core with a concentrated air gap) instead of a distributed air gap core will impact its behavior and parameters to calculate; for the first one, gap parameters as length are a priority.…”

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

“…Three configurations (toroidal, C cores with the core type winding, and C cores with shell type winding) of 1750-VA 5-kHz transformers were constructed from Vitroperm500F nanocrystalline cores [24]. The toroidal configuration exhibited the highest efficiency at 98.5% and the highest magnetizing inductance, whereas the core type structure had the lowest efficiency at 96%.…”