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Wireless power transfer (WPT) is an old subject, introduced for the first time by Nikola Tesla in the twentieth century [1]. His patent proposal was based on the magnetic resonance of two coils to distribute large amounts of energy to distant places of consumption. The subject returned to the mainstream in the last decade due to the exponential growth in the number of electronic devices. Currently, the main goal is to achieve ubiquity of WPT with the consolidation of the Internet of Things (IoT). How to supply the energy necessary to operate this huge network of gadgets is still a problem waiting for a solution. Three main aspects must be considered when outlining the powering strategy of those forthcoming technologies: small physical volume, high energy efficiency, and compatible aesthetics. Other emerging topics have similar requirements, such as battery-less medical implanted devices, remote contactless, and radio frequency identification (RFID), to mention a few. [ABSTRACT FROM PUBLISHER]

This paper presents a new approach to the classical method for failure detection with eddy currents. In contrast to traditional methods of measuring reflected impedance on the probe circuit, this paper uses concepts of identification theory to find a transfer function that characterizes the dynamics of the measuring system by eddy currents. The transfer function represents the admittance of the input equivalent circuit. The estimated parameters of the transfer function were used to compute the inductive time constant of equivalent circuit of the metal specimen. The results of the time constant variation of the equivalent circuit of the sample were compared with the equivalent input impedance variation. A preliminary analysis is done in a simple case study, which has shown that the inductive time constant is more sensitive than the reflected impedance on the probe circuit, especially at low frequencies. Moreover, the estimated time constant is independent of the excitation frequency and mutual inductance. [ABSTRACT FROM AUTHOR]

Wireless power transfer is a technique usually based on an inductive link, used for delivering energy to remote devices. The power of different applications ranges from microwatts to hundreds of kilowatts, e.g., in biomedical implants and electric vehicles. The transferred power is highly dependent on the relative position between the inductive link coils. Many studies have been presented considering static or quasi-static conditions, based on a fixed tuned circuit. However, when the coils are not stationary, the inductive link must be dynamically tuned to keep the designed output power. This paper presents a methodology for dynamically tune the inductive link by means of a variable capacitance. A voltage-controlled capacitance using concepts of the negative impedance converter and capacitance multiplier is proposed. The phase angle between the input voltage and current is used as the error signal to control the variable capacitance and keep the output power operating point. The experimental evaluation shows that the proposed methodology can significantly improve the power delivered to the load in comparison to a fixed inductive link. [ABSTRACT FROM AUTHOR]

This paper introduces the analysis of the efficiency and transferred power of an inductive link circuit with different network configurations of capacitors connected to primary and secondary coils. The best performance for both cited objective functions was observed with two capacitors connected to the input coil and two capacitors connected to the output coil. However, the output equations in this circuit configuration for both efficiency and output power are very complex and a numerical method had to be applied to compute the capacitors values. Since an exhaustive search would be long, some simplifications were assumed to reduce the search space and the processing time. Thus, a search algorithm based on a randomized method was developed and successfully applied. The results for both efficiency and output power of four capacitors configuration were compared with other usual approaches, such as the single and two capacitors compensation. Finally, a basic prototype was built and the theoretical results were validated. Both simulated and experimental results of the four capacitor configuration showed a significant improvement on the efficiency and output power of the inductive link. [ABSTRACT FROM PUBLISHER]