Showing papers on "Electromagnetic coil published in 2015"

Investigation of Multiple Decoupled Coil Primary Pad Topologies in Lumped IPT Systems for Interoperable Electric Vehicle Charging

Abstract: Today many vehicle manufacturers are interested in an inductive power transfer system design with a secondary side that is simple and low in cost, weight, and size. To achieve this, a more sophisticated primary side design is required to ensure interoperability with various magnetic topologies. Simple secondary pads such as the circular pad and double-D pad (DDP) (similar to the flat solenoid) can only couple either the perpendicular or parallel component of flux entering the surface of the pad respectively. This paper investigates using various known multiple coil pad designs as the primary that can be switched between various excitation modes during operation, without making tuning or other expensive adjustments. The primary pads considered here include; the DDP, the double-D quadrature pad (DDQP) and the bipolar pad (BPP). Results show that the mutually coupled structure of the DDP primary makes it a poor choice for interoperability, whereas the DDQP and BPP are able to achieve good results because of the decoupled coil structures inherent in their design. The DDQP has improved leakage characteristics while the BPP shows better interoperability characteristics with improved material usage efficiency and is easy to drive because of its identical coil structures.

Design and Experimentation of WPT Charger for Electric City Car

Abstract: Wireless power transfer systems (WPTSs) with inductive coupling are advantageously used to charge the battery pack of electric vehicles. They basically consist of coil coupling, power supply circuitry connected to the transmitting side of the coil coupling, and power-conditioning circuitry connected to the receiving side of the coil coupling. This paper presents the design and implementation of a wireless power transfer (WPT) battery charger for an electric city car. A short overview on the working principles of a series–series resonant WPTS is given before describing in detail the design procedure of the power circuitry needed for its operation, i.e., an alternating-current–direct-current converter cascaded by a high-frequency inverter in the transmitting section and a diode rectifier cascaded by a chopper in the receiving section. The coil coupling with spiral coils is designed with the help of a finite-element-method code. A prototype of the WPT battery charger is built up according to the design results, and experiments that validate the design procedure are carried out.

Integrated ${LCC} $ Compensation Topology for Wireless Charger in Electric and Plug-in Electric Vehicles

Abstract: This paper presents an integrated $LCC$ compensation topology for electric vehicle/plug-in hybrid electric vehicle wireless chargers. The effect of the coupling between the additional coil and the main coil on the $LCC$ compensation topology is studied. The proposed topology will reduce the size of the additional coil and make the system more compact with extremely high efficiency. The basic characteristics of the proposed topology are analyzed based on fundamental harmonic approximation. Furthermore, based on the steady-state model, three categories of operation modes are presented and analyzed. In order to realize zero-voltage switching, the series capacitor $C_{2} $ on the secondary side is tuned. A numerical method is used to analyze the impact of different values of $\Delta C_{2}$ on the turnoff current, and the best value of $C_{2}$ is chosen to build a prototype to verify the analysis.

Cordless indicia reader with a multifunction coil for wireless charging and eas deactivation

Abstract: A cordless indicia reader including a multifunction coil that can be configured to either transmit or receive electromagnetic energy is disclosed. In this way, the multifunction coil facilitates both the wireless charging of a battery and the wireless deactivation of electronic article surveillance (EAS) tags. The multifunction coil, and a plurality of modules to perform these functions, are integrated within the cordless indicia reader's hand-supportable housing.

Deployment and adjustment of airborne unmanned aerial vehicles

Abstract: This disclosure describes a power unmanned aerial vehicle (UAV) that may generate a current from a magnetic field of an overhead power line. In various implementations, while the power UAV is flying, the power UAV may receive another UAV at a platform. A control element of the power UAV may generate signals to cause the power UAV to fly to a location of a conductor of the power line. The control element may also determine a position of the secondary coil with respect to the power line and generate control signals to adjust the position of the secondary coil based on the determined position of the secondary coil, a determined safety distance, and/or a determined threshold distance for efficient current generation. A shielding substrate may also be provided to shield electronics of the power UAV or other UAVs from magnetic fields.

Loosely Coupled Transformer Structure and Interoperability Study for EV Wireless Charging Systems

Abstract: As the wireless power transfer (WPT) technology has been proved to be a convenient and reliable charging method to plug-in hybrid electric vehicles and electric vehicles, the loosely coupled transformer structure and size are the primary and fundamental concern to design an efficient WPT system. In this paper, a double D (DD) coil and a unipolar coil are selected to conduct the study. We focus on the coil structure design to achieve the maximum coupling coefficient as well as efficiency with two situations: 1) with no misalignment, and 2) with a 75-mm door-to-door and 100-mm front-to-back misalignment at which the maximum operating capability can still be achieved. A coil size optimization process is proposed for both the DD coil and the unipolar coil configurations. The relationship between the size of the secondary (receiving) coil, which determines the weight of the pad on the vehicle, and achievable maximum efficiency is studied for both coil topologies. The interoperability between the two coil topologies is studied. The proposed transformer structures with aluminum shielding meet human exposure regulations of the International Commission on Non-Ionizing Radiation Protection guidelines as a foundation. Finally, experiments validated the analyses.

A Methodology for Making a Three-Coil Wireless Power Transfer System More Energy Efficient Than a Two-Coil Counterpart for Extended Transfer Distance

Abstract: A new methodology for ensuring that a three-coil wireless power transfer system is more energy efficient than a two-coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The key features of the magnetic design are to: 1) shift the current stress from the primary driving circuit to the relay resonator; and 2) generate a large relay current for maximizing magnetic coupling with the receiver coil for efficient power transfer. Consequently, the current rating and cost of the driving circuit can be reduced and the overall quality factor and system energy efficiency are improved. This approach utilizes the combined advantages of the maximum efficiency principle and the use of relay resonator to overcome the energy efficiency problem for applications with extended energy transfer distances.

Global Fault-Tolerant Control Technique for Multiphase Permanent-Magnet Machines

Abstract: In this paper, a global fault-tolerant control (FTC) technique is proposed for multiphase permanent-magnet (PM) machine drives. The goal of the proposed FTC is to find a general closed-form solution for healthy phase currents under steady-state postfault conditions. Healthy phase currents are found through an optimization problem to produce ripple-free output torque with minimum ohmic losses. A comprehensive FTC approach should be able to provide fault-tolerant currents for multiphase machines with any number of phases. In addition, it needs to find currents based on fault type (open-circuit/short-circuit), fault locations [phase(s) and/or line(s)], connection of stator windings, and even different control objectives. An important feature of the proposed method is its flexibility and simplicity in dealing with all possible fault conditions. The proposed method is a great tool to evaluate fault-tolerant capability of different drive systems in terms of maximum available ripple-free torque and copper losses. Due to its simplicity and flexibility, it is also well-suited for real-time implementation. A five-phase PM machine is used as an example to investigate the validity of the proposed solutions through finite-element analysis and experimental tests.

The Rogowski Coil Principles and Applications: A Review

Abstract: The Rogowski coil is an old device for current measurement. It has been modified and improved over a century and is still being studied for new applications. The Rogowski coil has various advantages over conventional magnetic current transformers (CTs). Not only can it be used instead of CT, but also it has various utilizations in other fields. This paper provides a brief review on different aspects of the Rogowski coil and its advancement procedure, during last decades. In this paper, the history of the coil is brifely reviewed and its bases and applications are discussed. The Rogowski coil is analyzed from different points of view, including different integration techniques in the output stage, models for the Rogowski coil, experimental methods for parameter measurement in models, and method for determining the damping resistor. Finally, a brief review over different applications of the coil ends this paper.

System and method for power transfer

Abstract: A system for inductive power transfer that may selectively transmit power in a plurality of modes based on characteristics of a power receiver and determine which transmitter coils to drive based on received signal strength information. The inductive power transfer transmitter may detect characteristics of the power receiver in order to control the mode of the power transfer and selectively control which transmitter coils are driven based on signal strength information received from a power receiver. The power transmitter may have slugs formed of a magnetically permeable material within common coil winding openings and the transmitter coils may consists of a plurality of parallel windings.

Analyses of Transient Behaviors of No-Insulation REBCO Pancake Coils During Sudden Discharging and Overcurrent

Abstract: Stability margin of a high-temperature superconducting (HTS) coil is two or three orders of magnitude greater than that of a low-temperature superconducting coil. In recent years, many papers have reported test results of turn-to-turn no-insulation (NI) HTS coils having extremely enhanced thermal stability, such that burnout never occurs in an NI coil, even at an operating current exceeding 2.5 times the critical current. Thus, The main goal of this paper is to clarify transient electromagnetic and thermal behaviors and mechanism of the high thermal stability in an NI REBCO coil. A partial element equivalent circuit (PEEC) model is proposed for the numerical simulation of an NI REBCO coil, which considers a local electrical contact resistance between turns, an I-V characteristic of an REBCO tape, and local self and mutual inductances of the NI REBCO coil. Using the PEEC model, we investigate the influence of the turn-to-turn contact resistance on the transient behavior of the NI REBCO coil during sudden discharging. We also perform thermal conduction analyses with the PEEC model to clarify the transient behavior of an NI REBCO coil during an overcurrent operation.

High-Efficiency Transcutaneous Energy Transfer for Implantable Mechanical Heart Support Systems

Abstract: Inductive power transfer technology is a promising solution for powering implantable mechanical circulatory support systems, due to the elimination of the percutaneous driveline, which is still the major cause of severe infections. However, at the present time, no transcutaneous energy transfer (TET) system is commercially available and ready for long-term use. Specifically, the heating of the tissue due to power losses in the TET coils and the implanted electronic components are a major problem. The focus of this paper is, therefore, on the design and realization of a highly efficient TET system and the minimization of the power losses in the implanted circuits in particular. Parameter sweeps are performed in order to find the optimal energy transmission coil parameters. In addition, simple and meaningful design equations for optimal load matching are presented together with a detailed mathematical model of the power electronic stages. To achieve highest efficiencies, a high-frequency self-driven synchronous rectifier circuit with minimized volume is developed. Extensive measurements are carried out to validate the mathematical models and to characterize the performance of the prototype system. The optimized system is capable of transmitting 30 W of power with an efficiency greater than 95 %, even at a coil separation distance of 20 mm (0.79 in) and 70 mm (2.76 in) coil diameter.

Coupling Coefficients Estimation of Wireless Power Transfer System via Magnetic Resonance Coupling Using Information From Either Side of the System

Abstract: Wireless power transfer via magnetic resonance coupling method has opened a new possibility to the electric vehicle system. It allows the wireless charging system of moving vehicles, using charging lanes. However, although the efficiency of power transmission is relatively high, the efficiency still depends on displacement of coils. There have been several researches on methods to maintain power transmission at the highest efficiency. However, in such systems, the information on system parameter especially coupling coefficients is needed, and in the charging lane system, such information is unlikely to be obtainable without a communication system. Therefore, it has come to attention that parameter estimation is a crucial factor to implement a charging lane system. This paper presents derivations of equations for estimating coupling coefficients in several configurations of wireless power transfer system, using information from only one side, either the transmitting side or the receiving side, of the system. The presented equations are both applicable to the case of single receiving coil and are also generalized for the case of multiple receiving coils. Each equation is verified by both simulations and experiments. An experimental system of the coupling coefficient estimation system is constructed for estimation from the receiving side using a dc/dc converter.

Ultraslim S-Type Power Supply Rails for Roadway-Powered Electric Vehicles

Abstract: An ultraslim S-type power supply rail, which has a width of only 4 cm, for roadway-powered electric vehicles (RPEVs) is proposed in this paper. The cross section of the core has a thin S-shape, and a vertically-wound multiturn coil is displaced inside the core. In this way, the most slim power supply rail is designed, which is crucial for the commercialization of RPEVs. The construction of roadway infrastructure, which is responsible for more than 80% of the total deployment cost for RPEVs, can be much easier when the width of the power supply rail is so small. To increase portability and to minimize construction time, a foldable power supply module is also proposed in which flexible power cables connect each foldable power supply module such that no connectors are needed during deployment. An effective winding method for minimizing the cable length is proposed, and an optimum core thickness of the proposed power supply rail is determined by FEA simulations and verified by a prototype power supply module. By virtue of the ultraslim shape, a large lateral displacement of 30 cm at an air gap of 20 cm was experimentally obtained, which is 6 cm larger than that of the I-type power supply rail. In addition to the larger lateral displacement, it is estimated that the S-type one has lower EMF than the I-type one because the width of the S-type one is narrower than that of I-type one. The maximum efficiency, excluding the inverter, was 91%, and the pick-up power was 22 kW.

Design of a Universal Inductive Charger for Multiple Electric Vehicle Models

Abstract: Inductive power transfer technology has become a popular solution for battery charging of electric vehicles (EVs) However, problems such as varied magnetic coupling caused by coil misalignment still limit its practical applications, by safety and stability issues Meanwhile, the growing market of EVs asks for a universal charger for various models This paper presents the design process of a universal inductive charger (UIC) for EVs The proposed UIC is capable of adaptively providing a constant or controllable charging voltage to various EVs, with a wide range of varied magnetic coupling between the transmitting and receiving coils With a series-connected LC circuit, zero-voltage switching of the primary dc–ac inverter is universally realized in every charging cycle A simple yet effective control method based on the frequency variation is used to automatically select the optimal frequency in different coupling conditions and adjust the frequency during the charging process The design of the charging interface is also optimized with higher efficiency and power-transfer capability Simulations and prototypes validate that the proposed UIC is accurate, robust, and applicable

New Optimal Pulsewidth Modulation for Single DC-Link Dual-Inverter Fed Open-End Stator Winding Induction Motor Drive

Abstract: The multilevel topology with dual inverters feeding both ends of an open-end stator winding of an induction motor has been introduced around two decades ago. A common-mode inductor is usually required in series with motor windings to suppress zero-sequence or common-mode currents. In case of medium voltage high-power drives, low device switching frequency operation is preferred to improve the overall system efficiency. However, it increases the harmonic distortion of machine stator currents. Therefore, the goal of our study is to propose new optimal pulse width modulation to achieve: low device switching frequency, minimal harmonic distortion of machine stator currents, and elimination of zero-sequence currents. The main idea is to select the switching angles of two inverters such that zero-sequence components are eliminated and, then, perform optimization to determine switching angles that minimize the harmonic distortion of machine stator currents. The experimental results obtained from dual two-level and dual three-level inverter fed 1.5-kW open-end stator winding IM drive demonstrated the effectiveness of a proposed modulation technique.

Magnetic Field Energy Harvesting Under Overhead Power Lines

Abstract: Condition monitoring for overhead power lines is critical for power transmission networks to improve their reliability, detect potential problems in the early stage, and ensure the utilization of the transmitting full capacity. Energy harvesting can be an effective solution for autonomous self-powered wireless sensors. In this paper, a novel bow-tie-shaped coil is proposed, which is placed directly under overhead power lines to scavenge the magnetic field energy. Compared to the conventional method by mounting the energy harvester on the power lines, this approach provides more flexibility and space to power bigger sensors such as the weather station. As the harvesting coil cannot entirely enclose the power lines, the demagnetization factor that is closely related to the core geometry should be considered and optimized. Thus a new bow-tie-shape core is designed to produce a much lower demagnetization factor (hence more power) than that of the conventional solenoid. The selection of core material is studied and found that Mn–Zn ferrite is the most suitable core material because it greatly reduces the eddy current losses and also has high permeability. Experiment results show that the bow-tie coil could have a power density of 1.86 μW/cm 3 when placed in a magnetic flux density of 7 $\mu{\rm T_{rms}}$ . This value is 15 times greater than the reported results under the same condition. If a longer bow-tie coil with more turns is placed in a magnetic flux density of $11 \mu{\rm T_{rms}}$ , the produced power density is 103.5 μW/cm3, which is comparable to a solar panel working during a cloudy day. Thus, the proposed solution is a very efficient and attractive method for harvesting the magnetic field energy for a range of monitoring applications.

Homogeneous Wireless Power Transfer for Move-and-Charge

Abstract: This paper presents a homogeneous wireless power transfer (WPT) technique to continuously energize the moving target. Due to the mobility of the charging target, the misalignment between the primary and secondary coils inevitably deteriorates the energy transfer performance by adopting the conventional WPT technique, so the constant energization mechanism is the most important issue for move-and-charge systems. The proposed homogeneous WPT technique utilizes the alternate winding design to gaplessly assemble primary coils, aiming to enhance the magnetic flux density. Besides, the vertical-and-horizontal secondary coil is also implemented to further improve the capability of acquiring energy for charging targets, especially in the area of the coils gap. In such ways, the proposed homogeneous WPT technique can effectively fulfil a continuous charging mechanism for moving targets. Also, this paper deduces the equivalent circuit model to analyze the mutual effect among multiple primary coils, which offers the theory-based view for the design of move-and-charge systems. Besides, both simulation and experimental results are provided to verify the feasibility of the proposed homogeneous WPT technique for move-and-charge systems.

The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas

Abstract: The effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject’s head This implies that the direction of the induced electric field has a large effect on the efficiency of TMS To improve future protocols, knowledge about the relationship between the coil orientation and the direction of the induced electric field on the one hand, and the head and brain anatomy on the other hand, seems crucial Therefore, the induced electric field in the cortex as a function of the coil orientation has been examined in this study The effect of changing the coil orientation on the induced electric field was evaluated for fourteen cortical targets We used a finite element model to calculate the induced electric fields for thirty-six coil orientations (10 degrees resolution) per target location The effects on the electric field due to coil rotation, in combination with target site anatomy, have been quantified The results confirm that the electric field perpendicular to the anterior sulcal wall of the central sulcus is highly susceptible to coil orientation changes and has to be maximized for an optimal stimulation effect of the motor cortex In order to obtain maximum stimulation effect in areas other than the motor cortex, the electric field perpendicular to the cortical surface in those areas has to be maximized as well Small orientation changes (10 degrees) do not alter the induced electric field drastically The results suggest that for all cortical targets, maximizing the strength of the electric field perpendicular to the targeted cortical surface area (and inward directed) optimizes the effect of TMS Orienting the TMS coil based on anatomical information (anatomical magnetic resonance imaging data) about the targeted brain area can improve future results The standard coil orientations, used in cognitive and clinical neuroscience, induce (near) optimal electric fields in the subject-specific head model in most cases

An equivalent circuit grid model for no-insulation HTS pancake coils

Abstract: An equivalent circuit grid (ECG) model is proposed to analyse the time-varying characteristics of no-insulation (NI) ReBCO pancake coils. In the model, each turn of the coil is subdivided into fine elements in the azimuthal direction, and each element is equivalent to a circuit parameter. Then, the coil is equivalent to a circuit grid. A math model based on Kirchhoff's law is proposed to solve the circuit grid model. The distribution of the electrical current inside the NI coil is analysed for the charging and discharging process. A finite element method (FEM) model is coupled to calculate the magnetic field induced by the coil. To validate the model, a double pancake (DP) coil is fabricated by coated conductor ReBCO tapes. Charging and discharging tests are performed on the coil at 77 K. The results from simulations and experiments exhibit a good agreement. Then, this model is used for more studies on the current distribution inside the NI coil in the charging and discharging process. The charging and discharging delay of NI coil is analysed and explained by the model. The model can also be applied to partial insulated (PI) coils and magnets consisting of NI coils.

An electromagnetic inerter-based vibration suppression device

Abstract: This paper describes how an inerter-based device for structural vibration suppression can be realized using an electromagnetic transducer such as a linear motor. When the motor shaft moves, a difference of voltage is generated across the transducer coil. The voltage difference is proportional to the relative velocity between its two terminals. The electromagnetic transducer will exert a force proportional to current following the Lorentz principle if the circuit is closed around the transducer coil. If an electronic circuit consisting of a capacitor, an inductance and a resistance with the appropriate configuration is connected, the resulting force reflected back into the mechanical domain is equivalent to that achieved by a mechanical inerter-based device. The proposed configuration is easy to implement and very versatile, provided a high quality conversion system with negligible losses. With the use of electromagnetic devices, a new generation of vibration absorbers can be realized, for example in the electrical domain it would be relatively uncomplicated to synthesize multi-frequency or real time tunable vibration absorbers by adding electrical components in parallel. In addition by using resistance emulators in the electrical circuits, part of the absorbed vibration energy can be converted into usable power. Here an electromagnetic tuned inerter damper (E-TID) is tested experimentally using real time dynamic substructuring. A voltage compensation unit was developed in order to compensate for coil losses. This voltage compensation unit requires power, which is acquired through harvesting from the vibration energy using a resistance emulator. A power balance analysis was developed in order to ensure the device can be self sufficient. Promising experimental results, using this approach, have been obtained and are presented in this paper. The ultimate goal of this research is the development of autonomous electromagnetic vibration absorbers, able to harvest energy, convert it into usable power, and use it for vibration control and health monitoring.

Magnetic resonance wireless power transfer using three-coil system with single planar receiver for laptop applications

Abstract: 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.

Three-Dimensional Charging via Multimode Resonant Cavity Enabled Wireless Power Transfer

Abstract: The majority of existing wireless power solutions are capable of 2-D surface charging of one or two devices, but are not well suited to deliver power efficiently to large numbers of devices placed throughout a large 3-D volume of space. In this paper, we propose an unexplored type of wireless power transfer system based on electromagnetic cavity resonance. Here, we use the natural electromagnetic modes of hollow metallic structures to produce uniform magnetic fields which can simultaneously power multiple small receiver coils contained almost anywhere inside. An analytical model is derived that predicts the coupling coefficient and power transfer efficiency from the cavity resonator to a small coil. These predictions are verified against simulated results with a coefficient of determination of 0.9943. By using two resonant modes, we demonstrate that a 3-in diameter receiver can be powered in nearly any location in a 140 cubic foot test chamber, at greater than 50% efficiency. Additionally, we show that ten receivers can be powered simultaneously and that this system is capable of recharging consumer electronics such as a cell phone.

Analysis of Coplanar Intermediate Coil Structures in Inductive Power Transfer Systems

Abstract: Intermediate couplers have been shown to increase the coupling from primary to secondary pads in inductive power transfer (IPT) systems. This paper investigates embedding a coplanar intermediate coupler coil with the primary coil inside the primary pad to boost the coupling to the secondary pad and improve the efficiency of the system. Several coil designs are simulated and a mathematical model is developed to evaluate the efficiency of parallel–parallel and series–series tuned systems. As shown a coplanar, independently tuned intermediate coupler coil improves the efficiency of a series–series-tuned system since it reduces source losses. However, there appears to be no benefit to having an intermediate coupler with a parallel–parallel-tuned system. Furthermore, boosts in coupling are a result of adding extra current carrying windings to the primary pad and simulations show that operating the system as a traditional two coil IPT system may be simpler and more effective based on tuning topology. An experimental system was constructed to validate the simulations.

Free-Positioning Wireless Charging System for Small Electronic Devices Using a Bowl-Shaped Transmitting Coil

Abstract: This paper presents a wireless power transfer (WPT) system using a bowl-shaped transmitting (Tx) coil and its application for charging small electronic devices such as hearing aids and wearable electronic devices. The receiving (Rx) electronic devices are placed in the Tx coil and charged effectively with spatial freedom. The WPT system includes three coils for power transfer: a source coil, a Tx resonant coil, and a parallel-resonance Rx coil. The proposed Tx resonant coil is bowl shaped and made of spiral and conical-shaped helical coils in series. A compact box-like Rx coil with ferrite sheets in the box is designed to improve magnetic coupling. To analyze the proposed system, an equivalent circuit of the system is presented. Magnetic fields of the bowl-shaped Tx coil, as well as the mutual inductance between the Tx and Rx coils are derived. For the verification of theoretical analyses and calculations, a wireless charging system for hearing aids is fabricated. It is shown that the proposed system can uniformly charge a Li-ion battery with 30% overall efficiency in the parallel arrangement. Furthermore, even in the perpendicular arrangement, the battery can be charged, except for a narrow dead zone near the center of the Tx coil.

Design of a Resonant Reactive Shield With Double Coils and a Phase Shifter for Wireless Charging of Electric Vehicles

Abstract: In this paper, a novel resonant reactive shield using a double-shield coil and phase-shift circuit is proposed to reduce magnetic field leakage in electric vehicle wireless charging applications. The double-reactive shield with a four-capacitor phase shifter generates a canceling magnetic field, the phase of which is perfectly opposite to that of the incident magnetic field, effectively reducing the leakage magnetic field as a result. The concept and structure, and an equivalent-circuit model analysis of the double-reactive shield are explained and discussed. The shielding effectiveness of the double-reactive shield is compared with that of a conventional reactive shield with a single-shield coil by a simulation and is verified by experiments.

Magnetic recording head, magnetic head assembly, magnetic recording apparatus, and magnetic recording method

Abstract: A magnetic recording head includes a first magnetic pole, a second magnetic pole, a spin torque oscillator, a first coil, a second coil, and a third coil. The first magnetic pole applies a recording magnetic field to a magnetic recording medium. The second magnetic pole is provided parallel to the first magnetic pole. At least a portion of the spin torque oscillator is provided between the first magnetic pole and the second magnetic pole. The first coil magnetizes the first magnetic pole. A current is passed through the second coil independently of the first coil. A current is passed through the third coil independently of both the first coil and the second coil.

Hybrid-Excited Doubly Salient Synchronous Machine With Permanent Magnets Between Adjacent Salient Stator Poles

Abstract: A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated.