Comprehensive Investigation on the Influence of Magnetic Materials on the Weight and Performance of Onboard WPT Systems

Abstract

In an inductive power transfer (IPT) system, the magnetic core is usually used to improve the coefficient between the primary and secondary coils. However, considering the iron losses on magnetic materials, the addition of magnetic core may affect the system efficiency and, at the same time, increase the weight of the IPT system significantly. Therefore, in this study, the aggregate influence of thickness, permeability, and iron losses of magnetic core on IPT system performance is comprehensively investigated. First, the equivalent circuit model of IPT system is established, and the formulas for different types of losses are analyzed. Then, the three-dimensional models of the IPT system with magnetic core in different shapes are established to simulate the aggregate influence of core thickness, permeability, and iron losses. The simulation results reveal that reducing the core thickness requires a larger saturation flux density of magnetic materials. In addition, only if the material losses below a certain value and an appropriate core shape are adopted, the addition of magnetic material can improve the system efficiency. Finally, experimental validation on a 3-kW IPT system is performed under the conditions of no magnetic core, using ferrite core in radial pattern and hollow square shapes, and using nanocrystalline core with the thickness of 22 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m and 16 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m in radial pattern and hollow square shapes, respectively. The results show that the high efficiency and lower overall weight of the IPT system can be achieved when nanocrystalline core with suitable permeability and shape is used.