Abstract
This paper concerns the optimal design and comparative analysis of resonant and non-resonant high-frequency GaN-based rotating transformers. A multi-physical design approach is employed, in which magnetic, electrical, and thermal models are coupled. The results are verified by experiments. Two different optimization objectives are considered; firstly, the efficiency of two standard core geometries is maximized for a required output power level. Secondly, a geometrical optimization is performed, such that the core inertia is minimized for the desired output power level. The results of both design optimizations have shown large improvements in terms of output power and core inertia as a result of applying series–series resonant compensation.
Highlights
Wireless power transfer (WPT) is widely employed in applications that require reliable power transfer to rotating parts, e.g., in battery charging and robotic applications [1,2], as well as an alternative to slip rings or brushes in electric machines [3,4]
The high-frequency WPT system under consideration in this paper consists of a 48 Vdc supply, a dc/ac half-bridge converter, the WPT coils, and a single-phase rectifier including load
In order to obtain the reduction in core inertia, a higher electrical frequency is utilized (i.e., 850 and 950 kHz for the non-resonant and resonant design, respectively compared to 500 kHz for the optimal P18/11 design), which results in increased losses in the power electronics
Summary
Wireless power transfer (WPT) is widely employed in applications that require reliable power transfer to rotating parts, e.g., in battery charging and robotic applications [1,2], as well as an alternative to slip rings or brushes in electric machines [3,4]. A cylindrical transformer is used, which has a rotary and stationary side separated by a small air gap in either the radial or axial direction. A high magnetic coupling is achieved by the application of core material that has a high permeability [5]. A high-frequency power supply is typically applied, such that the transfer of power and efficiency are enhanced, whereas the volume of the transformer is reduced [6]. Gallium-Nitride (GaN) transistors have gained popularity in WPT applications, since switching frequencies in the range of several megahertz (MHz) are realized. Capacitors are placed parallel to, or in series with, the transformer winding on either or both the primary and secondary side, in doing so enhancing the Energies 2020, 13, 929; doi:10.3390/en13040929 www.mdpi.com/journal/energies
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