Finite-element-analysis of the mechanical behavior of high-frequency litz wire in flat coil winding
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Finite‑element‑analysis of the mechanical behavior of high‑frequency litz wire in flat coil winding Michael Weigelt1 · Cornelius Thoma1 · Erdong Zheng1 · Joerg Franke1 Received: 18 June 2020 / Accepted: 30 October 2020 / Published online: 17 November 2020 © The Author(s) 2020
Abstract Numerous applications of daily life use flat coils, e.g. in the automotive area, in solar technology and in modern kitchens. One common property that all these applications share, is a flat coil made of high-frequency (HF) litz wires. The coil layout and the properties of the HF litz wire influence the winding process and the efficiency of the application. As a result, the HF litz wire must meet the complex technical requirements of the winding process and of the preferred mechanical, electromagnetic and thermal properties of the HF litz wire itself. Therefore, a reasonable configuration and optimization of HF litz wire has been developed with the help of a finite-element-analysis (FEA). In this work, it is first shown that the mechanical behavior of HF litz wire under tensile and bending stress can be simulated. Since the computational effort for modelling an HF litz wire at the single conductor level is hardly manageable, a suitable modelling strategy is developed and applied using geometric analogous models (GAM). By using such a model, HF litz wires can be designed for the specific application and their behavior in a winding process can be predicted. Keywords High frequency litz wire · Flat coil winding process · Inductive power transfer system · Finite element analysis · LS-DYNA
1 Introduction High-frequency (HF) litz wire consists of hundreds of twisted and ultra-fine single wires in a complex geometric structure. In this work the application of HF litz wire in the winding process for flat coils of inductive power transfer (IPT) systems is going to be used as the validating example of the developed modelling technique. The coil in the primary pad side generates a magnetic field, which will induce a voltage in the coil in the secondary pad side, which allows electric power to be transferred over an air gap [1]. The shape * Michael Weigelt [email protected] Cornelius Thoma [email protected]
of the flat coil including the integrity of the HF litz wire’s cross-section is strongly coupled to the efficiency of the IPT system. Furthermore, the mechanical properties of the HF litz wire have an impact on the degree of automation of the winding process. The better the mechanical properties of the HF litz wire fit to the requirements of the winding process, respectively of the IPT system, the easier an automation of the process can be realized [1]. Many approaches for the design of HF litz wire, or stranded structures in general, are analytical and mostly simplified like presented in [2, 3]. A numerical approach has the potential to precisely predict the mechanical behavior of the HF litz wire based on the material parameters and the geometrical structure. Two distinct kinds of mechanical stre
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