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.
Fiber-reinforced polymers are increasingly being used, especially in lightweight structures. Here, the effective adaptation of mechanical or physical properties to the necessary application or manufacturing requirements plays an important role. In this context, the alignment of reinforcing fibers is often hindered by manufacturing aspects. To achieve graded or locally adjusted alignment of different fiber lengths, common manufacturing technologies such as injection molding or compression molding need to be supported by the external non-mechanical process. Magnetic or electrostatic fields seem to be particularly suitable for this purpose. The present work shows a first simulation study of the alignment of magnetic particles in polymer matrices as a function of different parameters. The parameters studied are the viscosity of the surrounding polymer as a function of the focused processing methods, the fiber length, the thickness and permeability of the magnetic fiber coatings, and the magnetic flux density. The novelty of the presented works is in the development of an advanced simulation model that allows the simulative representation and reveal of the fluid–structure interaction, the influences of these parameters on the inducible magnetic torque and fiber alignment of a single fiber. Accordingly, the greatest influence on fiber alignment is caused by the magnetic flux density and the coating material.
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.
The application of hybrid yarns and their further processing to textile preforms enforce adapted manufacturing processes. Furthermore, a consolidation of cross-section varying parts requires an adapted mold and core system for a reproducible production process. Similarly, the application of hybrid yarns facilitates low consolidation pressures and thus favors the integration of electronic components in fibre-reinforced thermoplastic parts. In this paper, the analyses of the boundary conditions for a process integration of sensor elements in complex fibre-reinforced spacer structures are presented.
If the energy transfer for charging the traction battery of an electric vehicle takes place wirelessly and with inductive components, the active area of the charging system must be monitored for safety reasons for the presence or intrusion of metallic objects that do not belong to the charging system. In the past, different concepts for such monitoring have been described. In this paper, passive inductive sensors are used and characterized based on practical measurements. With this type of sensor, the detectability of metallic foreign objects is very closely related to the characteristics of the magnetic field of the charging system. By optimizing the geometry of the sensor coils, the authors show how foreign object detection can be improved even in areas with low excitation of the foreign objects and the sensor coils by the magnetic field. For this purpose, a charging system, with which charging powers of up to 10 kW have been realized in the past, and standardized test objects are used. Furthermore, the thermal behavior of the metallic test objects was documented, which in some cases heated up to about 300 °C and above in a few minutes in the magnetic field of the charging system. The results show the capability of passive inductive sensors to detect metallic foreign objects. Based on the measurements shown here, the next step will be to simulate the charging system and the foreign object detection in order to establish the basis for a virtual development and validation of such systems.
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