Wireless power transfer (WPT), as a noncontact power transfer technology, is expected to solve the power supply difficulties faced by ocean power equipment due to the environment's complexity. However, when the magnetically coupled WPT system operates in seawater, eddy current losses (ECL) affected by the resonant frequency are generated, which in turn causes the resonant frequency characteristics of the system to be altered compared to those in air. The resonant frequency characteristics of WPT have been thoroughly researched, and expressions for the relationship between resonant frequency and efficiency have been derived by utilizing the mutual inductance circuit model with equivalent ECL resistance. The influences of resonant frequency variation on transmission efficiency and distance are comparatively analyzed for the system in seawater and in air, respectively, with the differences between the two situations further illustrated. Research has discovered that there is an optimal resonance frequency for WPT. The factors influencing the optimal resonance frequency were analyzed, and it was concluded that the contact area between the coil and seawater was the key factor affecting it. An experimental system for WPT in seawater media was constructed, and theoretical and simulation conclusions were validated through experiments.

In magnetic coupled wireless power transfer systems, two-dimensional planar coils or three-dimensional polyhedral coils are often used as coupling structures. Two-dimensional planar coils are sensitive to spatial position changes in the coupling structure. Although existing three-dimensional polyhedral coils can achieve omnidirectional high degree of freedom power transfer, they fail to meet the requirements for different levels of degrees of freedom in practical applications and inevitably experience energy waste during power transfer. To address this issue, a new reconfigurable three-dimensional coil structure is proposed, capable of generating a locally omnidirectional magnetic field and achieving limited omnidirectional wireless power transmission. This coil adopts a non-overlapping regular overall winding pattern, ensuring that each planar coil’s winding direction is different from that of adjacent planar coils, thereby enhancing the magnetic field between adjacent coils. Moreover, the coil features reconfigurable properties, effectively enabling the extension of degrees of freedom. By selecting different reconfiguration strategies, different levels of degrees of freedom can be generated, meeting the demands of various load conditions and reducing energy waste during power transfer. Experimental studies show that this system can achieve limited omnidirectional wireless power transmission and flexible extension of degrees of freedom, with an efficiency of 73%.

Due to the rapid attenuation nature of electromagnetic fields in wireless power transfer system within a large-scale spatial, it is difficult to realize spatial scale spanning to meet the current urgent demand for power supply of multi-loads electronic devices in unmanned indoor scenarios such as internet of things and automatic warehouse. In order to solve this problem, a novel transmitting structure with active relay coil is proposed in this paper for realizing power transfer at any location and number of loads within large-scale three-dimensional space. Firstly, the transmitter can be ensured that the winding directions of adjacent planar coils on the ceiling and floor of the space are different to increasing the magnetic field density; at the same time, the longitudinal direction of the magnetic field on the same side in the spatial region can be guaranteed to be the same, to extend the magnetic flux paths and the spatial transfer scale. Through experimental studies, 12 loaded light bulbs scattered in different positions within the space of 1.8m*1.4m*2.0m were all lit with the total efficiency of 80%, not limited to that number of loads. Under the single load, the minimum transfer efficiency is 8.2% and the maximum is 50%.

Nanocrystalline materials are widely utilized in high-frequency transformers due to their exceptional electromagnetic properties. Accurate loss prediction and effective hysteresis simulation for nanocrystalline materials are crucial for optimizing the design of high-frequency power electronic devices. This article presents a methodology for loss prediction and hysteresis simulation based on the loss separation theory and the Energetic hysteresis model. First, the hysteresis loss component is determined using the static Energetic hysteresis model. The real magnetic permeability is integrated into the calculation of the eddy current loss component, while accounting for the frequency-dependent behavior of conductivity. A skin effect coefficient is introduced to adjust the effective conductivity, which is subsequently employed to calculate both the eddy current and anomalous loss components. To model the frequency-dependent term of the anomalous loss, a cubic polynomial fitting approach is applied. Next, leveraging the principles of loss separation and field separation consistency, the total magnetic field intensity is expressed as the sum of the hysteresis field, eddy current field, and anomalous effect field. The impact of Energetic hysteresis model parameters on the hysteresis loop is thoroughly analyzed, and a shape factor is incorporated to accurately simulate the dynamic hysteresis loop. Shape factor parameters are further predicted using artificial neural networks. Finally, experimental measurements of nanocrystalline materials are conducted, and the prediction accuracy is assessed through error metrics such as relative error and root mean square error. The proposed wide-frequency loss prediction model demonstrates high accuracy, and the dynamic hysteresis simulation method proves effective.

1. Electromagnetic energy devices are widely used, especially in advanced fields such as electromagnetic launchers and railguns, where they play a crucial role. However, these applications face ext...