This paper presents a thermal investigation of lightweight on-board receiver modules of wireless power transfer systems for electric vehicles. The studied modules are capable of receiving up to 11 kW at a resonance frequency of 85 kHz over a distance of 110–160 mm. The receiver modules were built as sandwich and space–frame concept to design stiff and lightweight structures. The high transmission power of automotive wireless power transfer systems combined with the multi-part assembly of receiver modules led to challenges in heat management. To address this, the physical behaviour of the proposed lightweight concepts were studied on component and system level using a hardware-in-the-loop testing facility for wireless power transfer systems. Special emphasis was laid on the validation of a thermal simulation model, which uses analytical calculated power losses taking into account their temperature dependency. The proposed simulation model is consistent with the experimental validation of the critical active components. The performed systematic studies build the basis for a more sophisticated thermal dimensioning of various constructions for wireless power transfer modules.
The dimensioning of wireless power transfer systems requires compliance with safety standards for human exposure and electromagnetic compatibility. For this reason, shielding is conventionally carried out with heavy and costly plates. In order to evaluate a lightweight and low-cost alternative, this paper presents a comprehensive investigation of the shielding effectiveness of metal meshes in magnetic fields of wireless power transfer systems, including analytical modeling and experimental validation. Special emphasis is laid on the validation of novel analytical approximation approaches to model the anisotropic electrical conductivity of metal meshes. The proposed approaches show good consistency of the mean value taking into account warp and weft direction, whereas the modeling of the anisotropic behavior is not sufficiently accurately represented. Using the calculated electrical conductivity, the analytical modeling of the maximum shielding effectiveness based on a literature-known approach is very consistent for the experimental validation. Thus, the performed studies provide a significant contribution to the dimensioning of metal meshes as shielding for wireless power transfer systems.
The functional and spatial integration of a wireless power transfer system (WPTS) into electric vehicles is a challenging task, due to complex multiphysical interactions and strict constraints such as installation space limitations or shielding requirements. This paper presents an electromagnetic–thermal investigation of a novel design approach for an ultrathin onboard receiver unit for a WPTS, comprising the spatial and functional integration of the receiver coil, ferromagnetic sheet and metal mesh wire into a vehicular underbody cover. To supplement the complex design process, two-way coupled electromagnetic–thermal simulation models were developed. This included the systematic and consecutive modelling, as well as experimental validation of the temperature- and frequency-dependent material properties at the component, module and system level. The proposed integral design combined with external power electronics resulted in a module height of only 15mm. The module achieved a power of up to 7.2 kW at a transmission frequency of f0=85kHz with a maximum efficiency of 92% over a transmission distance of 110mm to 160mm. The proposed simulations showed very good consistency with the experimental validation on all levels. Thus, the performed studies provide a significant contribution to coupled electromagnetic and thermal design wireless power transfer systems.
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