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In this article, a special magnetic coupler for three-coil wireless power transfer (WPT) is proposed to eliminate the mutual inductance between the source coil and the receiver coil, which can significantly improve the design freedom. Specifically, unipolar Q coil, mixed QDD coil, and bipolar DD coil are designed for the source coil, the transmitter coil ($\text{T}_{\mathrm {X}}$), and the receiver coil ($\text{R}_{\mathrm {X}}$), respectively. By making use of unipolar coils and bipolar coils, this structure magnetically decouples the receiver coil from the source coil. Meanwhile, under different lateral misalignment conditions, this new coupler facilitates maintaining high efficiency. A laboratory prototype has been constructed to validate the proposed structure, demonstrating that the proposed structure can realize inherent characteristics, enhance misalignment tolerance, and energy transfer. The potential applications are EV systems, but this design can be generalizable to other three-coil systems. [ABSTRACT FROM AUTHOR]

Current imbalance in multistring light-emitting diodes (LEDs) is a critical issue. It may cause overcurrent in one or more LED strings, leading to rapid degradation. In this paper, a mixed high-order compensation networks-based wireless power transfer system is proposed to generate multiple constant current outputs. It is composed of an LCC resonant network in the transmitting side, a series resonant network, and multiple CLC resonant rectifiers in the receiving side. The CLC resonant rectifiers are connected in parallel to form multiple independent output channels, and each channel is then connected to an LED string. Based on the analysis of the T resonant circuit and the modeling of coupling coils, multiple constant output currents can be derived. As a result, current balance can be achieved, which is very suitable for driving multistring LEDs. The proposed system also offers a modular, scalable, and maintenance-free design, which can significantly reduce the construction cost and the control complexity. In addition, the inverter in the transmitting side can achieve zero phase angle. A laboratory prototype with dual independent output currents is built to verify the proposed method. The experimental results agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology has shown its significant role in various applications, such as electric vehicles and consumer electronics. In this paper, an input-parallel output-series circuit topology based on a compact double-sided decoupled coupler is presented to upgrade the power capacity of the WPT system with low-power and low-cost semiconductors. To avoid the potential risk of magnetic saturation, the phase difference between the transmitter currents is controlled to be 90° to achieve a symmetrical magnetic flux distribution for the magnetic coupler. Most importantly, an analytical model, which illustrates the relation between the efficiency and the ratio of the output voltages of the transmitter-side inverters under various misalignments, has been derived. Based on this, a control strategy is developed to maximize the energy efficiency under various misalignment conditions. The experimental results based on a 2.5-kW laboratory prototype show that, in comparison with the traditional method with identical inverters output voltages, the overall efficiency is improved by 2.32% by using the proposed method. [ABSTRACT FROM AUTHOR]

Dynamic wireless power transfer (DWPT) is a promising solution to address electric vehicle range anxiety and to reduce the capacity and the cost of the on-board batteries. In the traditional DWPT system, the mutual inductances among the transmitters make the design of compensation networks very complex. Besides, the power null phenomenon and the power pulsation phenomenon cause a fluctuating dc output voltage or current on the receiver side. To address these issues, this paper proposes a new magnetic coupler. Unipolar and bipolar coils are laid alternately to form segmented transmitters, which are turned on or off according to the position of the overhead receiver coil. LCC compensations, whose inputs are connected in parallel to a common inverter for cost reduction, are adopted. At the receiver side, unipolar and bipolar coils are overlapped in the same plate in order to effectively smooth out the mutual inductance variations and, hence, reduce the output voltage or current fluctuations. Also, a configurable resonant circuit is designed on the receiver side to achieve constant voltage charging and constant current charging. Moreover, an optimization design by using finite-element analysis software Maxwell is developed to choose the best turns of the receiver coil to further improve the output quality. A laboratory prototype with 4-A charging current and 96-V charging voltage, using 85 kHz operation frequency, is constructed to verify the proposed DWPT system. The experimental results show that constant and stable output voltage and current can be achieved with only ±2% fluctuation, and the overall efficiency is 90.37%. [ABSTRACT FROM AUTHOR]

Electric motors have a wide range of applications in a diverse range of industries. This paper presents a novel magnetic resonant coupling motor (MRCM), constructed without any iron or permanent-magnet core, i.e., a novel coreless and magnetless electric motor. Different from the conventional operation principle of existing electric motors, the application of the wireless power transfer system using magnetic resonant coupling technology is the key feature of the proposed MRCM. By adjusting the excitation frequency in accordance with the trajectory of resonant frequency splitting, a large electromagnetic force in different direction can be developed. Besides, the proposed MRCM has an inherent merit of unity power factor. This paper presents a new design concept, which could well be a promising start for a new generation of future electric motor. [ABSTRACT FROM AUTHOR]

In this letter, a multistring light-emitting diode (LED) driver based on a three-coil wireless power transfer system is proposed. The proposed system can solve the current imbalance problem among multiple LED strings because of its unique merit of multiple load-independent constant current (CC) outputs. Also, zero-phase-angle operation is achieved. Thus, not only the power rating of power switches can be reduced but also the efficiency is improved. For the sake of compactness, the source coil and the transmitter coil on the transmitting side are attached to the same plane. In addition, to further save the install space, magnetically integrated LCL resonators are utilized on the receiving side. The proposed system is cost-effective since only one receiver and passive components are needed to obtain the multiple CC outputs. Furthermore, by employing a master–slave control strategy, the output currents can be changed synchronously, which enables the “plug and play” capability and features a simple control structure. Finally, the feasibility of the proposed method is verified on a laboratory prototype. [ABSTRACT FROM AUTHOR]

In this letter, a compact battery charger based on wireless power transfer (WPT) technology without any communication requirement is proposed. Here, a new intermediate coil is developed to achieve load-independent constant current (CC) and constant voltage (CV) outputs. The intermediate coil is split into two coils and is overlapped with the receiver coil to form a compact structure. Two switches on the receiver side are used to reconfigure the intermediate resonant circuit in order to select different charging modes, i.e., CC mode or CV mode. The communication between the transmitter side and the receiver side as well as complex control strategies is not needed in the proposed structure. Besides, the proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which not only can lower the power rating of power devices but also improve the efficiency. A laboratory prototype with a 3.6 A charging current and a 48 V charging voltage is built to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This letter presents an inductive power transfer system based on a new variable coil structure to achieve load-independent constant current (CC) and constant voltage (CV) outputs for charging electric bicycles (EBs), without involving complex control strategies. The new variable coil structure consists of three-layer coils, i.e., two bipolar coils and one unipolar coil, on the transmitter side and one unipolar coil on the receiver side. The compact and portable receiver with series compensation is installed in the EB, while two switches on the transmitter side at the power charging station are utilized to reconfigure the transmitter coil structure to select the charging mode, i.e., CC mode or CV mode. The proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which will lower the power rating of power switches and improve the efficiency. A laboratory prototype is built to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]