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In the Tokamak device of controllable nuclear fusion, the poloidal field power supply (PFPS) provides the dynamic magnetic field inside the device. The power level of full-controllable devices has been improved with the rapid development of high-power semiconductor technology, which promotes the upgrade of poloidal field power supply. The PFPS adopts an AC–DC–AC circuit structure, which makes the load coil operate in four quadrants. Because the load is a superconducting magnet coil, the power of the load coil will change for a period of time to meet the demand of the internal magnetic field of Tokamak, resulting in the instability of DC bus voltage. This paper proposes an optimized bidirectional buck–boost active storage unit (ASU) with unidirectional inductor current, which can quickly make the bus voltage stable. In the circuit structure, the direction of the inductor current is unidirectional, which avoids the slow response of the inductor current in the reverse direction of the traditional buck–boost converter; And the inductor has a controllable freewheeling circuit, which can reduce the disturbance of inductor current to bus charging. The number of inductors is small, which avoids the large volume of traditional dual-inductor DC–DC converter; Compared with the traditional buck–boost converter, the buck–boost ASU with unidirectional inductor current improves the energy utilization of the bus capacitor. By establishing the mathematical model of the circuit topology, the dual closed-loop controller and modulation strategy are used to control the stable operation of the system. The simulation results show that the circuit structure can balance the bus voltage well and keep stable, when the load power changes suddenly.

Self-regulating high temperature superconducting (HTS) flux pump is one of the most effective methods to compensate the current degradation of a closed HTS magnet for its stable operation. In this study, to understand the working principle as well as the influential factors regarding to its operation performance, a basic circuit model has been established. Based on that, we found the saturation load current is strongly related to the added secondary resistance, which could offset the DC bias current induced in the charging loop. Then, we built a prototype experimentally, in which, part of the load coil was used as a HTS bridge and bifilar bridge design has been adopted to minimize the possible flux fluctuation in the load loop. In the experiment, the dependence of the charging performance on the bridge length as well as the added secondary resistance at different frequencies has been clarified. The results show that, the load current is remarkably impacted by the aforementioned parameters. Specifically speaking, with an increasing added secondary resistance, the operating frequency needs to be higher to ensure the secondary current can follow the primary current, which is crucial for maintaining a larger load current.

MacPherson strut suspension, which is widely used vehicle suspension type, decreases the riding comfort and durability of strut module due to the side load generated at the damper. In this study, a method for designing a C-type side load coil spring is proposed to reduce the side load, considering not only the centerline shape, but also the end coil angular position of the spring. The effect of end coil angular position as well as centerline shape on the force axis are analyzed through finite element analysis (FEA) and regression analysis. Formulas are established based on the analyses and the C-type coil spring was designed considering the effects of both design variables on the force axis. Then, the side load of the MacPherson strut suspension on which the designed C-type side load coil spring was mounted was calculated by using the flexible multibody dynamic analysis method. Finally, a side load reduction effect of C-type side load coil spring is analyzed by comparing with that of helical-type coil spring.

Wireless power transfer (WPT) systems based on magnetic resonance provides a possible method to supply energy for implantable medical devices, such as gastrointestinal robots and wireless capsule endoscopes. However, low power transfer efficiency (PTE) (most researches show it to be lower than 3%) and poor power received stability are the key limitation of WPT systems in such applications. Three-coil WPT systems are regarded as an effective method to improve the power transfer efficiency and power received of gastrointestinal robots. Thus, an analytical model of a three-coil inductive link was established in this paper. Then the power transfer efficiency of load coil was optimized by changing the coil turns and raising a novel coil configuration: a Helmholtz-like load coil. As a result, the power transfer efficiency and power deliver to load (PDL) of this three-coil WPT system are tremendously improved. To verify the proposed design, a prototype simulated the gastrointestinal robot working situation and it was implemented for an experimental test. The results obtained from the experimental test demonstrate that the proposed three-coil WPT system with 9 turns load coil and 40 turns receiving coil achieves a PTE of 4.32% and a PDL of 541.5 mW. Moreover, the best PTE attained by the novel Helmholtz-like load coil was 6.45% and the PDL was 845 mW.

This study presents an extremely small frequency-tunable monopole antenna operating at medium frequency/high frequency (MF/HF) band with an omnidirectional radiation pattern. Most of the existing miniaturisation techniques operate at low bandwidth as well as low efficiency. The design is based on a capacitive top, allowing the antenna to resonate at much lower frequencies, and a tunable inductive centre loaded. Utilising the capacitive top, the radiation resistance of the antenna is significantly increased. The resonant frequency can be tuned over a wide range of frequency (0.974–30 MHz) without changing the antenna total size by virtue of the tunable loading coil. The tuning system contains arms, motors, contactor, microcontroller and remote control. The experimental results are 0.0032 λ, ka = 0.01, |S 11| = − 15.8 dB, gain = −13.9 dBi and ɳ = 2.2% at its lowest resonant frequency.

The Space Plasma Environment Research Facility (SPERF) is a new ground-based experimental device for fundamental research studies on space plasma currently under construction at Harbin Institute of Technology in China. Scientific objectives of the SPERF include studying the asymmetric reconnection dynamics relevant to the interaction between the interplanetary and magnetospheric plasmas, reproducing the inner magnetosphere to simulate the processes of trapping, acceleration, and transport of energetic charged particles restrained in a dipole magnetic field configuration, and revealing the physical mechanism of the dipolarization front in the magnetotail. The device comprises a vacuum chamber, 11 coils consisting of 18 groups of sub-coils that are independently programmablely energized, and the plasma source system to provide the magnetic field and the plasma required by the physical experiments. Thus, each of these 18 groups of sub-coils requires a separate pulsed power supply; furthermore, the 18 pulsed power supplies constitute the pulsed power supply system of the SPERF of which the total storage energy is up to 18.3 MJ, and the technical challenges have to be overcome. The power supply energizing a dipole field coil (labeled OJC coil) wired by the copper wire to provide a dipole magnetic field is the most energetic power supply (labeled OJC power supply) with a 2.42 MJ, 16.8 mF capacitor bank charged to 20 kV. The OJC power supply delivers a current with a peak of 18 kA for a rise time of ∼26.69 ms, and the duration of the current is not less than 95% of the peak over 10 ms to the OJC coil. Meanwhile, the most challenging power supply is the power supply labeled poloidal field power supply with a 5.04 mF capacitor bank charged to 20 kV, which provides the excitation current for the load coil set with the current not less than 360 kA at the typical time of 0.11 ms to produce the sufficient growth of the magnetic field that the experiments need. In this paper, the overall design of the pulsed power supply system, the design concept of the modularization, and the principle selection basis of the key components are presented. The technical details of each power supply will be demonstrated in the future.

Wireless power transfer (WPT) is being developed to supply electric power to electric trains, using a source coil in/on the railway track and a pick-up coil on the train. A number of benefits can be obtained by eliminating the catenary and pantograph currently used for railway electric power supply. However, the WPT employs coils, and the electromagnetic field generated by the WPT can interfere with conventional train detection methods, such as track circuits and RFID, installed on the tracks. Train position information is critical for railway operation, especially for high speed trains. This paper proposes a novel system which provides train position information using a source coil segment. It consists of onboard sensor coils, ferrite blocks designed using specific position information, and a detector. The proposed system can be implemented using the source coil and load coil of the WPT. Information about the train's relative position is obtained by the detection of ferrite blocks distributed within the source coil segment. The train position information provided by the ferrite components is detected by onboard sensor coils and a detector. The proposed ferrite position identification (FPID) system provides accurate train position information and is not affected by WPT electromagnetic interference. The operating principles of the FPID system are presented in detail. The performance of the proposed FPID system was measured by simulations and experiments.

Five different glass sheathing devices were used to introduce 20 mL min−1 N2 sheathing gas around the effluent from the spray chamber to see the effect of their dimensions on plasma robustness as measured using the Mg II 280.270 nm/Mg I 285.213 nm emission signal ratio in inductively coupled plasma (ICP) optical emission spectrometry (OES). A clear relationship between device dimensions and the plasma robustness profile along the ICP central channel was observed. With an aerosol inlet having an inner diameter of 1.0 cm in the sheathing device, mixing of N2 with the aerosol was minimised and the resulting sheath increased robustness, the higher thermal conductivity of N2versus Ar likely improving energy transfer between the bulk plasma and the central channel. The configuration of the outlet is also important, as any bottleneck favours mixing of N2 with the aerosol, which in turn cools the plasma, thereby shifting the region of maximum robustness to higher above the load coil. Regardless of device dimensions, plasma robustness was always better with N2 sheathing gas. An increased ion-to-atom emission signal ratio also resulted for other elements than Mg. The presence of N2 also seems to affect excitation mechanisms, such as charge transfer between NO+ and Cd or Ni, which appears to take place at higher observation height, after N2 has had enough time to diffuse into the central channel.

An efficient short-range magnetic coupling wireless power transferring (WPT) system by embedding metamaterials (MTM) resonator between the source coil and load coil, whose configuration was designed based on topology optimization, was proposed in this paper. The topology optimization model for designing the MTM microstructures to achieve WPT with maximum power transfer efficiency (PTE) at the required frequency was established. The different MTM microstructures were realized by different conductor patch combination in the discretized pixelated design domain. As a designing example, a short-range magnetic coupling MTM-based WPT system with high efficiency at specific frequency 1 GHz was designed. Taking two classical MTM microstructures as reference, the PTE of WPT system with the topology optimized MTM was improved considerably. The variation of the transmission characteristics of the designed WPT system caused by misalignment was analyzed. The comparison between the MTM-based WPT system and the typical 4-coil WPT system was also discussed.

We have developed a new headstage architecture as part of a smart experimental arena, known as the EnerCage-HC2 system, which automatically delivers stimulation and collects behavioral data over extended periods with minimal small animal subject handling or personnel intervention in a standard rodent homecage. Equipped with a four-coil inductive link, the EnerCage-HC2 system wirelessly powers the receiver (Rx) headstage, irrespective of the subject's location or head orientation, eliminating the need for tethering or carrying bulky batteries. On the transmitter (Tx) side, a driver coil, five high-quality (Q) factor segmented resonators at different heights and orientations, and a closed-loop Tx power controller create a homogeneous electromagnetic (EM) field within the homecage 3-D space, and compensate for drops in power transfer efficiency (PTE) due to Rx misalignments. The headstage is equipped with four small slanted resonators, each covering a range of head orientations with respect to the Tx resonators, which direct the EM field toward the load coil at the bottom of the headstage. Moreover, data links based on Wi-Fi, UART, and Bluetooth low energy are utilized to enables remote communication and control of the Rx. The PTE varies within 23.6%–33.3% and 6.7%–10.1% at headstage heights of 8 and 20 cm, respectively, while continuously delivering >40 mW to the Rx electronics even at 90° rotation. As a proof of EnerCage-HC2 functionality in vivo , a previously documented on-demand electrical stimulation of the globus pallidus, eliciting consistent head rotation, is demonstrated in three freely behaving rats.

In this paper, a high-efficiency wireless power transfer (WPT) and force transfer system for a micro-robot is proposed. Two-coil systems are employed to power the micro-robot. The two-coil parts are ac and dc, and each consists of an external source and a load coil inside the micro-robot. In the ac coil part, the external source coil generates a time-varying magnetic field that is received by the ac load coil in the micro-robot as electrical energy. In the dc coil part, the external source coil is used as an electromagnet, which is used to generate propulsion force for the micro-robot. Through the proposed system, both the efficiency of electrical energy transfer and the generation of propulsion force can be significantly improved. The feasibility of the proposed approach was verified through simulation and experimentation results.

A magnetic resonance wireless power transfer (MR-WPT) system with a reconfigurable planar receiver (Rx) to optimize transfer efficiency (TE) for laptop application has been investigated. The proposed MR-WPT system consists of a general four-coil system: a source coil and a transmitter Tx) coil in a Tx part and an Rx coil and a load coil in an Rx part. To enable performance comparison, the Rx coil uses either a rectangular loop resonator or a slit ground resonator (SGR) and both resonators are connected with a p-i-n diode to reconfigure and optimize the MR-WPT system’s TE along the transfer distance between the Tx and Rx parts. Mobile devices, including laptops, need a ground plane for practical use; therefore, the Rx coil is replaced by only an SGR, which operates as both a resonator and a ground. This letter, experimentally and theoretically proves that a reconfigurable MR-WPT system with an SGR has sufficient efficiency without the ferrite sheet typically used in practical MR-WPT applications.

In the past two decades, there has been an increasing attention to develop an active locomotion system for in vivo wireless medical micro-robot applications. This will help achieve a capsule robot with more controllability for meeting various demands in practical clinical applications. In this paper, we present a new wireless active actuator with a simple structure, being able to drive the capsule robot (capsulbot) to move on a 1-D platform. Our study mainly focuses on the characteristics of both the actuator and the capsulbot under various controllable variables such as the frequency and the amplitude of the supply voltage. The propulsion of the capsule robot is produced by the collision action between an internal moving small coil and a wall permanent magnet (PM). This propulsion occurs every period when the current in the inner small coil suddenly changes to zero, and this enables the small coil to move toward the wall PM at a high speed due to a large magnetic attractive force. The motions of both the internal moving module and the capsulbot are greatly affected by the induced current in the load coil achieved by the Wireless Power Transfer (WPT) technology. The working principles of the active actuator and the wireless capsulbot are validated and tested experimentally on a wireless capsulbot prototype.

A vertical antenna with two sources is considered, where the second source replaces the traditional loading coil. Some positive properties of such an antenna are discussed., Рассмотрена вертикальная антенна с двумя источниками, где второй источник заменяет традиционную удлиняющую катушку индуктивности. Обсуждаются некоторые положительные свойства такой антенны., №1 (2019)

Purpose – Consider the mutual coupling between loads, the purpose of this paper is to study the total transmission efficiency based on different load coil positions relative to the charging platform, to provide the theoretical basis for the design and parameter optimization of one-to-multiple wireless charging platform. Design/methodology/approach – Based on the dual-load series-resonant wireless power transfer system, the expression of system efficiency and its calculation model is achieved using the equivalent circuit theory. Finally, a 96 kHz magnetic resonance wireless power transmission test platform is built up to verify the theoretical analysis given in this paper. Findings – For the completely resonant circuit, the transmission efficiency can be improved by increasing the transmitter-receiver coupling and reducing the coupling between receivers. The total transmission efficiency achieves its lowest value when two loads are with equal competitive capability. Originality/value – Through the simulation analysis of efficiency formula, the selection principle of impact factors can be applied to the optimization analysis of the transmission efficiency.

The invention of the negative feedback amplifier by Harold S. Black (1898-1983) in 1928 is considered one of the great achievements in electronics. In fact, it is listed among the IEEE Milestones, where it is credited to Bell Labs. Black was hired by Western Electric in 1921 and assigned to work on the Type C system, a newly introduced three-channel telephone network whose push-pull, vacuum-tube, repeater amplifiers produce too much harmonic distortion when connected in tandem [1]. At that time, telephone networks were spreading, and Bell Labs emerged quickly as the major research company in the telephone industry. The extension of lines over long distances required counteracting signal attenuation, which occurred, though at a reduced level, even in lines provided with Pupin's loading coils, which discretely increased the line longitudinal inductance L so as to match the Heaviside condition L/R=C/G for distortionless transmission (R being the longitudinal resistance and C and G the transverse capacitance and conductance, respectively).

This paper presents design and analysis of a switchable inductor suited for active impedance matching in magnetic resonance wireless power transfer systems. The switchable inductor is compact and can be used as both driving coil at transmitter side and load coil at receiver side. We first present the concept through design, simulation and measurement of a three loops coil where the inductance is selected using switches. This model of the driving coil is used to study the inner couplings between the loops. The coil was fabricated on PCB with inductances between 130-324 nH at the MHz region. In addition, we demonstrate a 10 loop driving coil for driving a high quality resonator with an almost linear increase in their mutual inductance, which is verified by measurement results.

The megagauss laboratory, ISSP, UTokyo has a long history of generation of megagauss fields, especially using the electro-magnetic flux compression, originated from the original work in 1970s. We have initiated a new project of 1000 T since 2011, and since then, we have been devoting ourselves to installation of the system and the technical improvements. Condenser bank units with 20 kV, 2 MJ for seed feed coils, and two set of main condenser bank units, 5MJ and 2 MJ each with 50 kV charging capability. The system comprising of those condenser modules has been installed, and operation tuning has been completed. The giant collector plates, and load coil clamping units are installed in anti-explosion chambers. Design of all those instruments was optimized to substantial improvement of the electro-magnetic field energy conversion efficiency. Our recent results of record magnetic field 1200 T obtained from our new megagauss generating systems is presented.

The wireless system with four-coil resonators is a popular configuration for mid-range wireless power transfer via magnetic resonance coupling. It has broad range of applications. But it is difficult to make the parameters of receiver (including receiving coil and load coil) to be consistent with the parameters of transmitter (including driving coil and transmitting coil) in different application environments. The parameters of receiving coil and load coil have strong impacts on efficiency of the wireless power transfer system. In this work, a comprehensive study on effects of receiver (including receiving coil and load coil) parameters, such as coils radius, wire radius, number of turns and length of coil, is conducted. Some important observations on the effects of the receiver parameters are drawn based on theoretical studies and PSPICE simulation, which are also verified by experiments. It is shown that the radius of receiver has more significant impacts on the power transfer efficiency than ot...

The load coils are employed for multiple loads of resonant wireless power transfer in this paper. With the addition of the load coil, this three-coil structure has easy access to transferring power to multiple loads with the advantages of a compact structure and controllable power flow. Both single-load transfer and multiple-load transfer are modeled and analyzed by means of the circuit theory. The transfer quality factor and the load matching factor are utilized in the analysis of efficiency. In the single-load transfer, the load matching condition is fully explored. Based on the single-load transfer, the multiple-load transfer is researched. The double-load transfer, acting as an illustration, is studied with the uncoupled and coupled load coils. Equivalent reflected resistances are introduced to decouple the model of the double-load transfer with coupled load coils mathematically. An experimental prototype is implemented to verify the aforementioned analysis. The experimental results agree with the theoretical calculations.

An innovative coupled magnetic resonance system (CMRS), introducing two lumped impedance transformers, is proposed. There are three major magnetic couplings between coils in CMRS: source-transmitter (Tx), Tx-receiver (Rx), and Rx-load couplings. Except for Tx-Rx coupling, other couplings do not directly contribute to wireless power transfer. Hence, in this paper, this miscellaneous coupling is replaced with a lumped transformer with ferrite core. Because there is only a Tx-Rx coupling, the CMRS becomes compact in size and robust to ambient changes. Moreover, the design of CMRS is drastically simplified without complicated multiresonance tunings due to little magnetic flux linkage from the source coil or load coil. Coreless coils are used for Tx and Rx coils to examine the characteristics of CMRS with lumped transformers. A detailed static analysis on the explicit circuit model of the proposed CMRS and design procedures are fully established. Experiments for 1- and 10-W prototype CMRSs with a class-E inverter at the switching frequency of 500 kHz, where the quality factors are less than 100, verified the usefulness of the proposed model, achieving 80% of the maximum Tx coil-to-load efficiency. It is concluded in this paper that the conventional CMRS, in general, is just a special form of an inductive power transfer system where the quality factor is extremely high.

Parts of certain objects need hardening. Hardening is a heat treatment process which can be achieved by induction heating. Certain objects like gears require alternating source with two different frequencies. Simultaneous application of dual frequencies is desirable for proper hardening of a gear. This study proposes a three-leg inverter topology with a load resonant circuit which can provide independent and simultaneous control of low-frequency (LF) and high-frequency (HF) currents through the load coil. The load circuit is a combination of two series resonant circuits which operates at the desired LF and HF. Power control is achieved with phase modulation and asymmetric duty cycle control techniques. A 240 W prototype of the proposed dual-frequency inverter is implemented and tested. Experimental results obtained are in good agreement with the simulation results.

This paper presents a magnetic resonance wireless power transfer (WPT) system that uses three coils, a planar receiver and operates at 6.78 MHz,. Effective power transfer is ensured by establishing an impedance matching condition for this WPT system. A metamaterial (MTM) array having dimensions of 20 cm Ⅹ 30 cm is also positioned near the load coil to concentrate the magnetic field and enhance the transfer efficiency. The result is a maximal improvement of 27% in the transfer efficiency at a transfer distance of 50 cm. The impact of a ground plane on the transfer efficiency is also examined. By utilizing the MTM array, making slits on the ground plane and increasing the gap between the ground plane and the load coil, it is possible to mitigate this impact. The highest transfer efficiency improvement is about 55% at a distance of 20 cm with the ground plane. A practical laptop model is fabricated to verify the impact of the load coil angle and position on the transfer efficiency. The result shows that the maximum transfer efficiency with the laptop model is 47.58% with the load coil angle of 90 degree.

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that use d two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improvedthe low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The wireless power transmission system haresonance d a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that hathe same resonance frequency. Therefore, two resonance coils were fabricatedd by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency

Wireless power transfer (WPT) can achieve safety, convenience, reliability, and suitability for special occasions like mining and implantable medical devices. Resonant WPT (RWPT) has received a great deal of attention in the last decade, through which a large amount of power can be transferred at a relatively long distance with high efficiency. In this paper, the four-coil structure of RWPT is modeled and analyzed. Three important factors are introduced. The analytical expressions of the system efficiency and the output power with a constant voltage source are deduced. The impacts of the source internal resistance, the load resistance, the mutual inductances of the source coil and the sending coil, the sending coil and the receiving coil (related to the transfer distance), and the receiving coil and the load coil are studied, and their optimal values to achieve maximum system efficiency and output power are obtained. The experimental results are in agreement with the theoretical calculations.

New probes for the direct measurement of high radio-frequency (RF) voltage and current in the load coil of an inductively coupled plasma (ICP) are presented. Based on these measurements, a method for the calculation of power in the ICP is developed. Electrical parameters of the ICP are measured for a wide range of operational conditions in a standard ICP torch with wet aerosol introduction. Further, changes of the electrical parameters are monitored when operating the ICP with a very low argon flow rate of only 0.6 L min−1 using a so-called “Static High-Sensitivity ICP” (SHIP) torch. Direct measurements with the new RF probes allow following the evolution of plasma properties as a function of time. Noteworthy, it is found that there is a strong correlation between the plasma power and temperature changes in the RF generator itself. Depending on the plasma parameters, the measured plasma power was shown to differ significantly from the applied power (in the vendor software settings).

Multiple loads need be charged from a single source in some practical scenarios, such as a charging platform for many consumer electronics, wireless charging for sensor networks. Different application scenarios require different multiple-load structures.

Electronic devices rely on chargers and cables to power up batteries, and the battery drains faster with respect to the increase of usage. Wireless power transfer has now become the key solution to power up electronic devices using air as the transmission medium. This paper performs simulation result of 4-coils resonance structure which is applicable in mid-rage wireless power transfer. The number of turns of the transmitter and receiver coils are varied to observe the magnetic and electric field transmission. Result shows that at a higher number of coil turns, higher electric field, magnetic field and scattering parameter are transmitted from the source to the load coil.

In a magnetically coupled resonant (MCR) wireless power transfer (WPT) system, adding repeating coils is an effective way to lengthen transmission distance and improve the transferred power in a wide range. This paper investigated a 3-coil MCR WPT system. Based on fundamental harmonic analysis on the equivalent circuit model, the relationship between the transmission characteristics and the spatial misalignments of coils were derived in detail. To improve the robustness of the output power to the spatial scales, one can adjust the position of the repeating coil to ensure the mutual inductances between sending and repeating coils, receiving and repeating coils be proportional when the spatial scales of load coil varies. To verify the theoretical analysis, a prototype of the 3-coil MCR WPT system was built and the experimental validation were carried out.

During the recent years, researchers have made extensive evaluations in Induction Heating (IH) technology related to user friendliness and efficiency improvement. Owing to this advantage, traditional IH cook-tops are typically employed for preparing food at domestic as well as restaurant level. Using an induction heating, the vessel is directly heated without thermal inertia. Here, the method is proposed in which the fluid will get heated directly from the coil. Implementations of mild steel and stainless steel load coils are prepared for selecting the efficient heat transfer to fluid. The experimental results show that the efficiency of the stainless steel load coil increases nearly by about 24% as compared to traditional methods and by 3 to 5 % by the mild steel load coil. The application can be adopted for industries, medical appliances, restaurants, bathrooms, dining halls, and many more.

This paper reports a 2.48 GHz tri-coil and rectifier design implemented in a system that demonstrates simultaneous wireless power transfer and communication to a 0.1 mm by 0.1 mm coil. The tri-coil link and rectifier successfully rectified and demodulated a 20 dBm amplitude-shift keyed (ASK) RF signal modulated at a rate of 1 Mb/s. Additionally, a 5.7 GHz tri-coil link was fabricated to validate the frequency scalability of this technology platform for other unlicensed bands and was measured in a customized experimental testbed to account for the effects of lateral misalignment between coils. The 5.7 GHz tri-coil design had a measured peak RF power transfer efficiency of −29 dB with a vertical separation of 1 mm, which is ten times the load coil diameter.

This paper proposes an autonomous coil alignment system (ACAS) for electric vehicles (EVs) with dynamic wireless charging (DWC) to mitigate the reduction in received power caused by lateral misalignment between the source and load coils. The key component of the ACAS is a novel sensor coil design, which can detect the load coil's left or right position relative to the source coil by observing the change in voltage phase. This allows the lateral misalignment to be estimated through the wireless power transfer (WPT) system alone, which is a novel tracking method for vehicular applications. Once misalignment is detected, the vehicle's lateral position is self-adjusted by an autonomous steering function. The feasibility of the overall operation of the ACAS was verified through simulation and experiments. In addition, an analysis based on experimental results was conducted, demonstrating that 26% more energy can be transferred during DWC with the ACAS, just by keeping the vehicle's load coil aligned with the source coil.

The detection of closed cracks is crucial to the assessment of the integrity of metal structural components. In recent years, the ultrasonic nonlinear technology has been increasingly utilized in such detection. With this technology, the vibro-acoustic modulation (VAM) technique is found to be reliable and sensitive. In this study, the technique is implemented through electromagnetic loading to enhance the sensitivity of ultrasonic detection and evaluation of closed cracks. The proposed VAM technique based on electromagnetic loading involves opening and closing of the closed crack with Lorentz force emanating from the loading coil and magnet instead of mechanical equipment, which can concentrate the loading energy around the closed crack rather than on the whole specimen. The opening and closing of the closed crack can enhance the nonlinearity effect when ultrasonic signal propagates through it. The comparative experiments performed in this study demonstrate that the proposed VAM technique based on electromagnetic loading has a considerable potential in the ultrasonic evaluation of closed cracks. The influence of different electromagnetic loading parameters on the modulation effect are also investigated experimentally.

SummaryInduction hardening is a heat treatment process which selectively heats parts of work-piece with different size and shape. Components like gears require different frequencies with inner core requiring low frequency and outer surface requiring high frequency. Simultaneous application of low and high frequency currents is desirable for proper hardening of gear. This paper proposes a two inverter topology with a load resonant circuit which can provide independent and simultaneous control of low and high frequency currents through the load coil. The load circuit is a combination of two series resonant circuits which operates at the desired low and high frequencies. Power control is achieved with phase modulation of low and high frequency inverters.

This paper reports a newly developed high current transformer-rectifier High-Tc Superconducting (HTS) flux pump switched by dynamic resistance. A quasi-persistent current of over 1.1 kA has been achieved at 77 K using the device, which is the highest reported operating current by any HTS flux pumps to date. The size of the device is much smaller than traditional current leads and power supplies at the same current level. Parallel YBCO coated conductors are used in the transformer secondary winding as well as in the superconducting load coil to achieve high current. The output current is limited by the critical current of the load rather than the flux pump itself. Moreover, at over 1 kA current level, the device can maintain high flux injection accuracy, and the overall flux ripple is less than 0.2 mili-Weber. The work has shown the potential of using the device to operate high field HTS magnets in ultra-high quasi-persistent current mode, thus substantially reducing the inductance, size, weight, and cost of high field magnets, making them more accessible. It also indicates that the device is promising for powering HTS NMR/MRI magnets, in which the requirement for magnetic field satiability is demanding.

Wireless power transfer via magnetically resonant coupling is a new technology to deliver power over a relatively long distance. Here, we present a mat-based design to wirelessly power moving targets based on this technology. Our design is specifically applied to transcutaneously power medical implants within free-moving laboratory animals. Our system comprises a driver coil array, a hexagonally packed transmitter mat, a receiver coil, and a load coil, and generates a nearly flat magnetic distribution over a defined area to produce an approximately constant power output independent of the location of the receiver coil. This paper also describes a novel power receiver coil design of the same shape as the exterior of the implant, allowing for maximum magnetic coupling, eliminating the space restrictions due to the coil within the implant, and matching the resonant frequencies of the implant and the transmitter coil. Our new transmitter and receiver designs significantly reduce the size of a biomedical implant and may provide a lifetime power supply to implanted circuits without the need for an internal battery. Our designs are also useful in various other applications involving moving targets, such as part of a robot or a vehicle.

A hybrid optimal design strategy for wireless magnetic-resonant charger of deep brain stimulation devices is presented. It is proposed that a differential evolution algorithm with discrete variables (turn numbers of coils) and constrains (induced current and voltage in the load loop) is used to design the wireless power transfer system. The variables which normally include the sizes of the load coil, receiver coil, transmitter coil, source coil and capacitances are analyzed in the optimization study. Analytical formulas are embedded in the numerical optimization to speed up the convergence of the searching process. The designed receiver can receive enough power to recharge a 3.7 V circular button-type nickel-metal hydride rechargeable battery which can be implanted into the patients' skull. The performance of the designed system has been verified experimentally.

This paper presents the new coil design strategy for Wireless Power Transfer (WPT) applications. In order to produce better power transfer efficiency for remotely located load, hybrid approach is proposed using two different coils such as conical and spiral. Hybrid approach refers the coil model by engaging conical as a transmitter and spiral as a receiver in a single system. The field pattern of conical coil is cumulative so that better magnetic field is possible at the bottom side for high directivity. In contrast, the spiral coil produces distributive field pattern so that the field distribution is uniform. Taking advantage of these two different behaviors, better power efficiency would be achieved by reducing power loss in the coil zone. For this hybrid approach, Finite Element Method (FEM) based conical and spiral coils were developed and simulated to determine field patterns and their value. Two different prototypes (Conical and spiral) were experimented with fixed spiral load coil to validate the performance of the hybrid approach. The output load coil voltage and efficiency plots were made based on the measurement, for analyzing the system performance. It is recorded the efficiency of 72% with the optimum distance 10cm and biasing voltage 10V respectively. The results from simulation as well as experiment confirms that hybrid approach could support significantly to reduce power loss and increase the relative operative distance.

Objective: The main theme of this paper is to analyze the wireless power transfer system efficiency in real time with different medium, distance and angle between the source and load coil. Analysis: The transmitter side of Wireless Power Transfer (WPT) system connected to the supply and receiver side is connected with load. The analysis is carried out for 2, 3 and 4 coil system in experimental test setup. Based on the experimental results it has been observed that the 4 coil WPT system gives better performance as compared with other two. Also it shows higher efficiency, if the angle of orientation of the load coil is small with the source coil.Findings: The four coil WPT system can be used in low power wireless charging devices with the distance of 3 to 15c.m between transmitter and receiver. Application: This system can be employed in electric vehicle charging, Bio implants, microrobots and so on.

Multiple power repeater coil antennas for coverage area extension of a wireless battery charging system are presented in this paper. The low-profile repeater coil is simply constructed using a copper wire and a capacitor. The transmitter resonant coil (Tx), the repeater resonant coils (Rp) and the receiving resonant coil (Rx) are arranged in a planar configuration. Experiment results with two Rp coils are presented to demonstrate the charging range extension. The power transfer efficiency is investigated by the analysis of the scattering parameters of the system as a two-port network with a reference impedance of 50 Ohm. The operating frequency is chosen at 6.78 MHz according to the A4WP wireless battery charging standard. As the power source, a 10 Watt class-E RF generator circuit was used. The load coil which absorbs the energy via magnetic coupling from the Rx resonant coil is connected to a converter circuit which provides 5V constant DC voltage for battery charging of portable devices. The optimum impedance matching is considered for all coupling stages by optimizing the distance between the resonant coils. It is found that the charging area in the horizontal plane can be extended with the proposed multiple Rp coil antennas.

A method of placing an electromagnet between the source and load coil of a wireless power transfer (WPT) system to increase lateral misalignment tolerance have been proposed. By implementing an electromagnet, the flow of magnetic flux can be controlled, thus allowing larger power magnitude and tolerance even with increased misalignment compared to conventional WPT systems. The proposed method has been verified using 3-D simulation analysis.

Several operating parameters for single-droplet analysis by inductively coupled plasma‐atomic emission spectrometry were investigated and optimized. Two plasma observation modes, both of which measure the plasma side-on, were compared. In the “whole-vertical” mode, the entire vertical emission pattern of the center portion of the central channel was spatially integrated, whereas in the “lateral” mode emission from a thin horizontal slice of the vertical plasma image was measured. The limits of detection (LOD) as well as measurement precision attainable by these two observation modes were found to be practically identical. However, the lateral mode is preferred because emission is then more insensitive to a small drift in carrier-gas flow than in the vertical mode. Precision was found to degrade at carrier-gas flows that yield maximum sensitivities in both observation modes. As a result, the best precision and lowest LODs cannot be achieved under the same plasma operating conditions and a compromise is needed. In this study, precision was given a higher priority than LOD because each individual droplet is regarded as a new sample in single-droplet analysis and each such sample can be measured only once. For best precision, the observation region should be 3 mm downstream of the atomization site to avoid the adverse local plasma cooling effect of the vaporizing particle. Under optimized conditions, the best precision is about 3–4% and the absolute detection limits for eleven elements (Ag, B, Ca, Cd, Cu, Fe, Mg, Ni, Pb, Sr, and Zn) range from sub-single to hundreds of femtograms, which corresponds to 106 to 109 atoms for single-droplet analysis. In addition, a new synchronization trigger method for droplet analysis was developed. This method is based on Hα emission collected between the first and second lowest turns of the load coil. This trigger signal fires while the droplet is still intact, resides inside the lowest portion of the load coil, and is typically around 1 to 2 ms ahead of the atomization event. Jitter between this trigger signal and analyte emission is typically less than 100 μs, and is precise enough for correct timing for signal acquisition and integration.

This paper is tried to analysis the optical emission spectroscopy related to the position of inductive load coil and flow rates of methane and oxygen in the RF inductive plasma process. According to the position of load coil, peak of , , and CH were appeared strongly at the middle position of the coil and it decreased both direction. The electron temperature was approximately 0.9[eV] at that position. Emission intensities of , , and CH increased linearly by increasing input power. In addition, intensities of and increased by increasing the flow rate of oxygen. It might be ascribed that the oxygen species were bonded with by suppressing the combination with hydrogen atoms. Consequently, the optimal position of the inductive coil is decided to the intermediate position between 4th and 5th turns, the wanted carbon thin-film is possible to deposit by controlling flow rates of methane and oxygen.

The company JEMA has delivered to the Joint European Torus (JET facility at Culham) the enhanced radial field amplifier (ERFA). This device is a high frequency, high power amplifier aimed at correcting instabilities due to fast plasma disturbances. The system is composed of four identical units connected in series through a connection box delivering up to ±12 kV, ±5 kA (60 MVAr) in four quadrant operation. Each unit is composed of an input converter stage, a DC link energy storage stage, an output inverter and an output bypass (for continuing operation in case of a unit failure). ERFA works as an energy exchanger between the internal DC link capacitors bank and the JET radial field coils. The input converter compensates for power losses in the JET coils and the ERFA during operation. The ERFA control system is fundamental for the amplifier performance to meet the speed of response required with the flexibility to achieve this for an unpredictable reference and for a wide range of load coil configurations. This paper covers the control architecture, the real-time evaluation and high speed response to the system requirements, and the fast exchange rate of data among ERFA units.

Computer simulation results of the flux compression generator (FCG) loaded with an inductor has been presented in this paper. Simulation research has been performed in order to select the parameters of FCG load coil properly. The influence of the load inductance and resistance on the current gain factor and the magnetic field energy accumulated in a load coil has been investigated.

This paper deals with detection and localization of load coils in the copper access network. The load coil is a legacy device that must be removed before deploying broadband services on twisted-pair transmission lines. The proposed methods do not require dedicated hardware but utilize the already installed transceivers for one-port measurements of the line input impedance. The number of load coils is detected by counting the number of resonance peaks in the line impedance spectrum. An approximative model of the symmetric loaded line is presented, from which a low-complexity load coil locator is derived. For nonsymmetric lines, a load coil locator using model-based optimization is proposed. The two methods are compared and evaluated by computer simulations and by laboratory measurements on real transmission lines. The estimation results indicate that up to five load coils can be robustly detected and located with the proposed methods.

Functionality of wireless power transfer is yet to be utilized for the purpose of sustaining a green environment. This paper presents a critical review on the functionality of mid-range wireless power transfer using magnetic resonance coupling. Simulation of a 4-coils magnetic resonance for mid-range wireless power transfer is performed using CST microwave studio. The radius of source and load coil are 3 cm, while the radius of the transmitter and receiver coil are 5 cm. Distance between the source coil and load coil is set at 4 cm and resonance magnetic frequency is observed. At the load coil, electric field is achieved at 2140 V/m and surface current is recorded at 52.21 A. The change in impedance along the transmittance are plotted and discussed.

In this paper, we propose a novel coil structure, using a ferromagnetic material which concentrates the magnetic field, as the propulsion system of a wireless power transfer (WPT) based micro-robot. This structure uses an incident magnetic field to induce current during wireless power transfer, to generate a Lorentz force. To prevent net cancelation of the Lorentz force in the load coil, ferrite films were applied to one side of the coil segment. The demonstrated simplicity and effectiveness of the proposed micro-robot showed its suitability for applications. Simulation and experimental results confirmed a velocity of 1.02 mm/s with 6 mW power transfer capacity for the 3 mm sized micro-robot.

Wireless power transfer via magnetic resonant coupling is experimentally demonstrated in a system with a large source coil and either one or two small receivers. Resonance between source and load coils is achieved with lumped capacitors terminating the coils. A circuit model is developed to describe the system with a single receiver, and extended to describe the system with two receivers. With parameter values chosen to obtain good fits, the circuit models yield transfer frequency responses that are in good agreement with experimental measurements over a range of frequencies that span the resonance. Resonant frequency splitting is observed experimentally and described theoretically for the multiple receiver system. In the single receiver system at resonance, more than 50% of the power that is supplied by the actual source is delivered to the load. In a multiple receiver system, a means for tracking frequency shifts and continuously retuning the lumped capacitances that terminate each receiver coil so as to maximize efficiency is a key issue for future work.