Direct and quadrature (DQ) rotating magnetic-field-based transmitting (Tx) coils for wireless charging of multiple internet of things (IoT), which are broadly distributed over three-dimensional (3D) spaces, are newly proposed in this paper. The proposed Tx coils provide a uniformly distributed DQ magnetic field environment so that numerous IoT, such as active radio frequency identification (RFID) tag, electric shelf label (ESL), appliances, and various sensors connected to internet, are charged with 3-D omnidirectional wireless charging. By virtue of the generated DQ magnetic field, six degrees of freedom (6-DoF), regardless of their three-axes positions and directions, are achieved by the proposed Tx coils with plane receiving (Rx) coils, which is essential for the proposed ubiquitous wireless power environment. Therefore, the proposed wide-range ubiquitous inductive power transfer (IPT) is highly recommended for adoption in practical applications, where volumetric structures with large size of core are not allowed. The optimum distance between the DQ lines of the proposed Tx coils d _w was found by magnetic field analysis to deliver maximum magnetic fieeld B _t at a target distance of z ₁ . To generate DQ currents and guarantee zero-voltage-switching operation of the main switches, detailed static analysis of the proposed DQ Class D inverter based on an imaginary gyrator model is presented. The effective area ratio of an Rx coil having a ferrite core is derived and experimentally found in this evenly distributed magnetic field condition. 1:20 and 1:1 scaled-prototypes for d _l = 10 m and 5 m DQ line cases, respectively, were installed on the ceiling and experimentally verifed for the uniformity of magnetic field and the highest wireless power delivery freedom. Experimental results showed that the proposed IPT has 78% of uniformity for magnetic field and Rx coils are freely charged with a 6-DoF characteristic. Two hundred of Rx coils, which are arbitrarily distributed over 3-D space, can be simultaneously charged with 16.2 W of total received load power and 9.3% of power efficiency.

A dipole-coil-based inductive power transfer (IPT) with a reflector, which first adopts the variable switched capacitance for load power regulation under very wide-range distance variation between transmitter (Tx) and receiver (Rx) coils, is newly proposed. The resonant frequency of the LC tank of the proposed IPT can be appropriately modulated by the variable switched capacitance with reliable zero-voltage-switching (ZVS) operations. Therefore, even though the distance changes very widely, load power can be regulated solely by the variable switched capacitance in the Rx circuit without complicated communication links between the Tx and Rx coils. A detailed static analysis based on a recent imaginary gyrator model and design procedure for the proposed IPT are presented to build a simplified LC resonant tank of the proposed IPT and ZVS condition and to identify applicable distance variation range for constant load power. A prototype of the Tx and Rx coils for 100 W of load power, considering average power consumptions of home appliances, was fabricated and verified by simulations and experiments, which showed that load power was completely regulated to 100 W for 23-70 cm of very wide-range distance variation at a fixed switching frequency of 140 kHz.

A new conductive-plate-integrated inductive power transfer (IPT) system for automated guided vehicles (AGVs) with little output power variation according to air-gap changes between the transmitter (Tx) and receiver (Rx) is proposed. The inductance change of the ferrite core due to variations in the air-gap is nullified by a corresponding change in an aluminum plate. Compared to conventional ferrite IPT systems, self-inductance of the proposed Tx coil is little changed against air-gap variations, which results in robust resonant frequency and output voltage. The self-inductance was experimentally verified to remain within 0.45% even when the air-gap changes by fivefold from 10 mm to 50 mm. The output power variation became a twelfth of that of the conventional ferrite IPT for air-gap variations of 30 ~ 50 mm, where the efficiency was found to be 96.0% when the output power was 1 kW.

A new curved-type reflector for solar power generation is proposed. By adopting the curved-type reflector between consecutive solar panel arrays, all incoming sunlight can be utilized and thus, the generated power is significantly increased. Furthermore, the proposed curved-type reflector can be generally used in four seasons regardless of the altitude or angle of the installation environment. The optimum design rule for the curved-reflector, comparing to a plane-type reflector, is completely developed in this paper. A new solar cell configuration best fit for the proposed curved-reflector is also provided. Experimental results showed that the curved-type reflector improves the spatial average solar power by 61% compared to no reflector case, which is even 11% higher than the plane-type reflector. Reflectors, especially curved-type reflectors, are found to be one of promising solutions for highly efficient solar power generation.

A sliding EE transformer (SEET) rail, which has a strong and independent magnetic coupling to the gap variation between the transmitter line and receiver coil for powering the sliding door, is newly proposed. In the proposed structure, the magnetic coupling can be maintained as strong and constant even though the receiver coil moves along the door rail when the sliding door is closed or opened. Through detailed coil designs based on electric and magnetic circuit analyses, design constraints on voltage, output power, flux density, and zero voltage switching are proposed with a closed form solution of output voltage. The SEET rail is designed to provide a maximum load power of 200 W for the sliding door within ambient temperatures from -40 °C to 125 °C. The proof-of-concept prototype shows a strong magnetic coupling, k = 0.76 at 20 °C and the variation of the magnetizing inductance with respect to the temperature variation was measured as 13.8%. The maximum power transfer efficiency excluding the regulator was 85% at a nominal load power of 100 W, and the efficiency at the maximum load power of 200 W was measured as 82% with a 3%P variation by the temperature variation.