Abstract
An increment of magnetic field strength inevitably appears at the shield edge if a magnetic shield is made of a soft magnetic material, and that increment becomes more serious if this shield is combined with the chassis of an electrical vehicle (EV). This phenomenon is caused by the fringe effect, which limits the transfer efficiency of the coupler for the wireless power transmission (WPT) systems of EV. This phenomenon, and its relationships with some parameters, are analyzed in this paper, and these relationships are fitted to estimate the increment for different shield structures. A magnetic shield structure to reduce the increment of the magnetic field strength and improve coupler efficiency is herein proposed. The effectiveness and correctness of the fitting curves and the advantages of the proposed shield structure are demonstrated by finite element analyses results.
Highlights
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For the secondary shield of the soft magnet material, the relationships between the increment of the magnet field strength by the fringe effect and some parameters including the radius, depth, relative permeability and input power of the coupler are obtained in this paper by the linear fitting and correlation analysis methods to estimate the increment values due to the influence of the fringe effect
The basic structure of a WPT system for EV is shown in Figure 2, which includes a power-frequency rectifier and its filter, a high-frequency inverter, a primary side compensation circuit, a secondary side compensation circuit, a high-frequency rectifier and its filter and loose coupler are combined as mainly as a WPT system, where the loose coupler is the key for transferring energy by high-frequency magnetic field
Summary
In order to prevent serious air pollution, EV and hybrid EV (HEV) are widely used to replace the fuel vehicle and reduce gas(HEV). Since the chassis is always made from a hard magnetic material such as steel or aluminum alloy, the shield can be seen as a double layer This phenomenon becomes more serious if the adopted material has larger relative permeability and the shield has double or multiple layers; the transfer efficiency is affected due to the increased strength. For the secondary shield of the soft magnet material, the relationships between the increment of the magnet field strength by the fringe effect and some parameters including the radius, depth, relative permeability and input power of the coupler are obtained in this paper by the linear fitting and correlation analysis methods to estimate the increment values due to the influence of the fringe effect Based on these relationships and estimated value, an improved shield with an extended part is proposed to prolong the radius indirectly and reduce the influences of the fringe effect.
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