SF ₆ decomposition products could reflect the running status and inner faults of power equipment, and it's expected to realize a timely warning. In this work, six faults including spark and corona discharge were simulated, and SF ₆ decomposition products with various types and contents were obtained as well. Different from previous investigations employing precision instruments, such as gas chromatography and infrared spectroscopy, a micro sensor array loaded with three gas-sensitive nanomaterials was used to discriminate fault characteristic gases, performing obvious advantages in small size, high integration, and rapid detection. Gas chromatography-mass spectrometry (GCMS) indicated that seven analytes had significant differences in types and contents. Meanwhile, the as-prepared micro gas sensor array also outputted significantly various signals for seven analytes, which provided a basis for gas identification. With the assistance of stacked denoising autoencoder (SDAE)-based discrimination algorithms, the recognition model between the response signals of the array and the discharge faults in power equipment could be established. In comparison with KNN (66.67 %), decision tree (70.47 %), and BPNN (73.33 %), SVM has achieved the highest average accuracy of 75.23 %. Totally, this work provides a promising novel method for rapid on-site inspection of SF ₆ -insulated power equipment.

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.

Omnidirectional wireless power transfer to multiple devices has become a research hotspot due to its high spatial freedom and flexible design. However, this power supply method often faces the problems of high leakage flux and different receiver power requirements. This article studied the effects of currents of transmitting coils on transmission efficiency mathematically. A method of maximum efficiency tracking and power allocation for omnidirectional wireless power transfer to multiple receivers was proposed, and a mutual inductance identification method based on primary feedback is presented. Through the parameters identified by the primary side feedback, the current amplitudes and phases of the Tx coils were adjusted to achieve maximum efficiency, and the flexible power requirements of multiple devices can be realized. Finally, the above methods are experimentally verified. The two receivers can be charged with 58.8% efficiency and the power ratio can be precisely controlled from 0 to 100 percent, which is difficult for conventional method.

To expedite the laborious design and optimization of resonant coils in wireless power transfer systems, many traditional modeling methods are studied to calculate the coil inductances based on simplified coil structures. However, coil layouts are oversimplified in these studies, especially ignoring the corners of rectangular coils, thus leading to unavoidable low calculation accuracies. Aiming at these issues, precise parametric structure models are proposed for the circular and rectangular coils, which particularly model the corners of rectangular coils as elliptic arcs for the first time. Moreover, based on the parameterized coil structures, precise parametric inductance models are developed to achieve accurate and fast inductance calculations for coils with and without ferrite plates. Particularly, the complex mutual inductances between elliptic corners and other sections in rectangular coils are precisely analyzed and modeled. Through extensive theoretical calculations and experimental verifications, the proposed parametric inductance models not only exhibit higher calculation accuracies than traditional methods but also demonstrate much faster calculation speeds than finite element method (FEM) simulations. Specifically, the proposed models for circular and rectangular coils can enhance the mean accuracy in inductance calculation by more than 13% than traditional methods. Moreover, the proposed model implemented with MATLAB and Python programs is about 3 and 6 times faster than FEM simulations, respectively.

Capacitive power transfer (CPT) system takes advantages of being able to transfer power across metal with low power losses, so it is potential for mobile desktop applications such as mobile phones, tablet PCs, laptops, etc. Compared with single transmitter and single pickup (STSP) CPT systems, single transmitter and multiple pickup (STMP) CPT systems are more competitive in cost and convenience. However, a big challenge in existing multipickup CPT is the outputs vary greatly when the transmitter and the pickup are not aligned. This article proposes an interdigital electrode capacitive coupler to realize antioffset performance of multiple pickups. Then, for ease of analysis, an STMP to STSP conversion CPT model is proposed to simplify mathematical analysis. By designing double-sided LC topology, multiple pickups are regarded as a parallel branch of the compensation network on the primary side, and the STMP system is converted to a STSP system. Finally, the load-independent CC outputs of multiple pickups and the antioffset performance of the proposed CPT system are analyzed, and the zero voltage switching state can be also obtained. A prototype with single transmitter and three pickups was built, load-independent CC outputs and antioffset performance of multiple pickups have been verified. The system efficiency was up to 91.7% (28 W) in the case of three pickups.

The surging applications of low-power sensors and portable electronic devices require a safe, convenient and low-cost charging method which draws interests of the wireless power transfer research field. Conventional WPT techniques using resonant coupling structures are limited by complexity, safety concerns and hardware costs. Electromechanical wireless power transfer (EWPT) techniques provide a low-cost, easy-to-control and safe wireless charging method via moving magnets; but transmission failures may occur due to the position and orientation misalignments of loads from optimum conditions. This article proposes an EWPT system that is able to charge loads at different tilt angles via a low-frequency rotating magnetic field and a permanent magnet rotor. The magnetic field has a uniform distribution in a space volume over 125 000 mm ³ . A custom permanent magnet rotor embedded with six identical cylindrical magnets and an induction coil is employed to capture transmitted power. Theoretical analyses and experimental results are presented to prove the feasibility and output capability of the proposed system. The peak output power achieves 130 mW under a magnetic field strength around 1 mT and the system output maintains stable for loads at different tilt angles. Such EWPT method can be applied as a stable power supply for free-positioned and free-oriented sensors or other low-power devices in an enclosed or semienclosed area.