As wireless electric vehicle charging (WEVC) technology moves toward commercialization, understanding its associated risks is crucial, particularly with the trend toward high-power fast charging. In this paper, thermal risks and factors exacerbating the risks in wireless EV chargers are investigated comprehensively, focusing on the magnetic coupler and foreign objects (FOs) intruding on the charging area. The power losses and temperatures of the coupler and FOs are obtained using a two-way electromagnetic-thermal coupled model, and the coupler will be assigned to a risk level according to the proposed four-temperature-level risk evaluation mechanism. In this model, practical considerations include coil types, misalignments, FO materials, ambient temperatures, etc. Moreover, a dynamic perspective is used to characterize the trend of risks so as to provide predictive insights. To validate the newly identified risks, two 6.6-kW WEVC prototypes are built employing circular coils and DD coils, respectively. Experimental studies confirm the necessity of implementing thermal risk management strategies for magnetic coupler under misaligned conditions such as enhanced cooling, including a wider range of materials for foreign object detection (FOD), expanding the FOD area, and so forth.

Metal object detection (MOD) is indispensable for wireless electric vehicle charging (WEVC) systems for safety concerns. Most recently, interests are growing in MOD by electromagnetic (EM) sensing. However, current works based on EM sensing rarely target the systems with DD coils, a promising coil type for commercialization. Additionally, EM sensing schemes are mostly derived from a mindset, viz., cooperation between two sensing coils to obtain the voltage difference as a MOD criterion. Hence, undesired out-of-phase incident becomes an inherent problem jeopardizing the success rates of detection. In this article, noncooperative MOD, which solely relies on the voltages of individual sensing coils rather than cooperative ones, is proposed with absolute confidence in detection results. A unique sensing coil array is devised to suit the field characteristics of DD coils perfectly. Size-modulated patch coils are created to eliminate the undetectable zones with proper polarity configuration. Moreover, virtual double-layer sensing coils are constructed to enhance MOD's reliability. Tested by 13 different positions and three types of MOs using a 3.0-kW WEVC prototype, the induced voltages reach at least four times the threshold value. Moreover, the stability of the proposed method is verified successfully no matter the system operates in light-load or heavy-load conditions.

Wireless charging systems (WCSs) are considered very appropriate to recharge underwater surface vehicles (USVs) due to their safe, flexible, and cost-effective characteristics. The small depth of immersion of USVs allows a WCS operated at an mm-level distance using a dock. Resultant tight coupling between the transmitter and receiver is conducive to high power, yet faces a challenge to alleviating misalignment sensitivity. In addition, considering USVs’ endurance, the weight of a WCS should be strictly limited. In this paper, a 6.0 kW underwater WCS is analyzed, designed, and optimized, which achieves a good balance of power capacity, misalignment tolerance, and onboard weight. A multi-receiving-coil structure is employed, which is crucial to large misalignment tolerance. On this basis, two types of coils adapting the hull shape of USV, viz., curved and quasi-curved coils, are devised and compared in case the hydrodynamic performance of USV is degraded. Finally, the weight of receiver is effectively reduced using bar-shaped ferrite without sacrificing the power capacity of WCSs. The results indicate a merely 8.73% drop in coupling coefficient with misalignment ranging from 0 to 100 mm. Moreover, ferrite use is reduced by 40.48 kg compared to a ferrite sheet, which accounts for 50.28% weight of the receiver.

With the growing use of unmanned surface vehicles (USVs) for underwater exploration, efficient wireless charging solutions like inductive power transfer (IPT) are crucial for addressing power limitations. This paper presents a novel IPT system for USVs and introduces a systematic design approach for optimizing magnetic couplers. The proposed design addresses three critical challenges: misalignment tolerance, lightweight construction, and thermal safety, which are intricately linked through a magnetic field. In terms of misalignment, this paper demonstrates that the coil length is a key factor in determining misalignment tolerance. For a lightweight design, replacing the ferrite plate with ferrite bars can significantly reduce the weight of the coupler without causing core saturation. The design is further validated through a two-way coupled electromagnetic–thermal simulation. The results reveal that, with proper thermal management, the system avoids thermal risks in underwater environments compared to air. Finally, a 3 kW prototype is constructed and tested in fresh water, achieving 55 V and 50 A wireless charging at an 85.7% full-load dc-to-dc efficiency, thus confirming the practicality and performance of the design.

High brittleness severely restricts the practical use of nanocrystalline cores in low-frequency power electronics. To enhance mechanical strength and facilitate cutting and transportation, curing techniques are commonly employed, yet their influence on the magnetic properties of the cores remains unclear. In this work, three curing techniques, namely, fluid-phase adhesive curing, gel-phase adhesive curing, and vacuum-evacuated gel-phase adhesive curing (VGAC), are applied to prepare cores with varying curing degrees. The magnetic properties of them are quantitatively compared with those of uncured cores within the range of 50–550 Hz. Results show that all three curing techniques demonstrably reduce the eddy current losses of the cores. Specifically, the VGAC-based core exhibits a 50% reduction in eddy current loss compared to the uncured core at 550 Hz and 0.8 T. Meanwhile, high saturation flux density is retained in all cured samples. However, curing also reduces permeability and raises coercivity. Furthermore, cured cores demonstrate increased hysteresis and residual losses, leading to higher total losses. The relationship between core losses and temperature rise is also investigated to provide important guidance for the safe operation of cured cores. In addition, microscopic images under 200× magnification are presented to elucidate the mechanisms underlying these observed influences.