Abstract
Underwater wireless power transfer (WPT) has gained a lot of popularity in recent years. In the seawater environment, the electrical conductivity is non-negligible compared with that in the air. Therefore, the eddy current loss is generated by the high-frequency alternating currents in the coils. The eddy current loss of the aligned coils has been analyzed while the eddy current loss of the misaligned coils has not been explored yet, which is crucial because misaligned coils are more common in practical applications. In this paper, an analytical model for the eddy current loss of a coreless WPT system in the seawater with misalignments is established with Maxwell’s equations. The theoretical expressions of the electric field intensity and the eddy current loss are derived. Then the eddy current loss is analyzed under different misalignments and frequencies. It is found that the efficiency in the seawater remains stable at a frequency range of 215.5 kHz to 248.4 kHz. Moreover, the efficiency is relatively unchanged under a small lateral misalignment and decreases sharply when the lateral misalignment keeps growing. An underwater WPT prototype is built and the experiments verify the theoretical analysis.
Highlights
Wireless power transfer (WPT) technology has been widely studied in recent years, which can be applied in numerous situations,[1,2,3] such as autonomous underwater vehicles (AUVs).[4,5,6,7,8,9,10]
It is interesting to note that the efficiency in the seawater remains stable at a frequency range of 215.5 kHz to 248.4 kHz, which is because the efficiency in the air increases in this frequency range, while the eddy current loss becomes significant from nearly 215.5 kHz, which will resist the increasing efficiency with the resonant frequency
The eddy current loss has been analyzed under different misalignments and frequencies
Summary
Wireless power transfer (WPT) technology has been widely studied in recent years, which can be applied in numerous situations,[1,2,3] such as autonomous underwater vehicles (AUVs).[4,5,6,7,8,9,10] Energy is a major factor restricting the long-term continuous operation of the AUV in the ocean. An underwater WPT system based on a semi-closed core structure was proposed to study the power losses comparatively in air, freshwater and seawater, and the overall efficiency was analyzed.[8] A single-turn model of a circular coil with a ferrite core was proposed to calculate the eddy current loss of the underwater WPT system.[9] the ferrite was assumed to be infinite, which is not precise. To the best of the authors’ knowledge, there are few references, if any, studying the eddy current loss of the underwater WPT system with a lateral misalignment. The calculation model based on Maxwell’s equations to calculate the eddy current loss of the underwater WPT system with lateral misalignments is proposed.
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