Search

The torque ripple of a switched reluctance motor (SRM) should be taken into account, as it can have negative effects on a connected gearbox and/or load. In this paper a concept and two realization methods for the reduction of the torque ripple are presented. An optimized alignment of the active elements of the stator leads to a reduction of this torque ripple. The first method proposed here is a four-fold segmented motor, which can reduce the torque ripple by 37.3 %. This can be achieved by segmentation in combination with a clever arrangement of active elements. However, this increases the number of necessary inverters, which increases redundancy and therefore leads to more security. A second method of achieving an equal reduction can be obtained by using a “double stator” motor. In this configuration both stators can be powered together. With this concept, the number of converters is halved compared to the first mentioned solution. This saves electronic components and thus reduces the effort. All results referred to in this article are obtained by simulation, or measured on a prototype. [ABSTRACT FROM AUTHOR]

This paper presents a novel leakage model for transformers that includes losses. This new model is physically based (topological) and it is possible to connect it to a topological core model without using any fictitious windings. The methods to calculate its parameters from standard test data and from design data are detailed within the paper. The results show that the new coupled leakage model with losses is able to match exactly the test report, when using standard test data. Preliminary investigations show that the results are very close to measurements, when using design data. [ABSTRACT FROM AUTHOR]

This paper aims to propose a new Vernier reluctance machine (VRM), which integrates the advantages of a robust rotor structure, good torque density, and flexible flux control ability. The key is to establish the excitation field with both stator slot permanent magnets (PMs) and zero-sequence current. Two excitation sources have different pole pair numbers but share a parallel magnetic circuit and contribute to superimposed torque in this machine. Meanwhile, a flexible flux control can be achieved by regulating zero-sequence current, and little demagnetization risk exists for slot PMs during flux control. In this paper, the machine configuration and operation principle are introduced, along with its integrated ac and dc drive method. Electromagnetic performance of this new machine is evaluated by finite-element analysis. Leading design parameters are determined and optimized considering optimal injection ratio of zero-sequence current. A prototype is fabricated, and relevant experiment results demonstrate the feasibility of the proposed solution. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology has become a popular research direction in the field of industrial applications, with the advantages of contactless operation, high degree of freedom, and great controllability. However, there are still some challenging issues that need to be resolved. First of all, more advanced circuit topologies and magnetic coupling structures need to be designed to achieve the power conversion goals of diversified applications. Second, novel control methods, optimization algorithms, and modeling methods enable systems to be better controlled and designed. Finally, potential application scenarios need to be discovered so that this novel power transfer method can be applied in more suitable applications. Therefore, this topic is organized by the responsible editor to gather the power of more scholars. With reviewers' hard work and considerations, 32 papers were finally accepted for publication in this Special Issue. [ABSTRACT FROM AUTHOR]

For a marine electrical machine, its high power density and large electromagnetic (EM) load tend to bring high saturation to the magnetic circuit. When the non-linearity of ferromagnetic material is not taken into consideration, large errors will appear in the calculation of air-gap flux density and EM force wave. Considering the radial and tangential EM force waves that cause the stator core to vibrate and deform are the primary sources of EM vibration of a non-salient pole synchronous generator (NSPSG), this paper introduces a semi-analytical method of calculating the radial and tangential EM force waves, with the non-linearity of ferromagnetic material taken into account. The method includes the distributed magnetic circuit method (DMCM), the separation variable method (SVM) and the complex variable conformal transformation method (CVCTM). First of all, the radial air-gap flux density is obtained by using the DMCM to calculate the no-load magnetic circuit of the NSPSG and dealing with the non-linearity of ferromagnetic material by B-H curve. Then, the tangential air-gap flux density is calculated by the SVM and the complex relative air-gap permeance is calculated by the CVCTM to determine the effect of slotting. Finally, the radial and tangential EM force waves are obtained by Maxwell stress tensor method. The proposed semi-analytical method is verified through measuring vibration acceleration of the NSPSG. [ABSTRACT FROM AUTHOR]

The transverse flux permanent-magnet (PM) linear machine has attracted much attention in high-performance direct-drive applications because of its high torque density and efficiency. However, due to its inherent large open-circuit flux leakage, the prominent cogging force makes it difficult to obtain a high accuracy in position and speed control, which restricts its potential for precision industrial processing applications. To overcome this problem, a novel transverse flux linear machine is proposed in this paper. The key is by creatively combining a consequent-pole mover design and a stator-segment-interlacing configuration in such a way that a parallel and complementary transverse magnetic circuit is realized for the moving PMs, which can effectively minimize the open-circuit leakage flux and cogging effect. In this paper, the machine structure, operation principle, and theoretical modeling are introduced, with its electromagnetic performance evaluated by using the finite-element method. A prototype is also built for the experimental verification, and relevant test results agree well with the finite-element predications. [ABSTRACT FROM AUTHOR]

A novel multi-function saturated-core fault current limiter (MFCL) with two operating modes is proposed in this paper. MFCL can achieve fault current limitation and power flow management by switching operating mode: current-limiting mode and power-flow-controlling mode, which realizes technology convergence. The MFCL consists of an iron core with rotatable magnetic valve, ac coils, dc coils, and a fault-limiting reactor. The operating principle of the MFCL and the design of the rotatable magnetic valve are analyzed in this paper. The finite-element analysis (FEA) model based on Maxwell is used to analyze the MFCL. Simulation results depict that the MFCL can limit fault current effectively and provide variable impedance for power flow controlling. [ABSTRACT FROM AUTHOR]

Torque motor is one key component that directly influences the dynamic performance of jet pipe servo valve in aircraft. In this paper, a novel torque motor with hybrid-magnetization pole arrays is proposed. By changing the magnetization patterns of permanent magnets, the torque motor can significantly improve the output torque by range of 47–52% compared with traditional designs, while maintaining the system size and mass. The design concept and operating principle of the torque motor is presented. The magnetic field distribution is formulated analytically with equivalent magnetic circuit. Different from conventional study, the flux leakage of the permanent magnets and coils is included to improve the model precision. Subsequently, the output torque is derived mathematically from the airgap flux. Following that, the numerical calculation is conducted to validate the mathematical models of magnetic field and output torque. The design optimization is then carried out. One research prototype that can be mounted with either conventional magnet or the proposed hybrid array has been developed. The test rigs are constructed and experiments are conducted on the prototype. Both numerical computation and experimental results verify the significant improvement of torque generation of the proposed hybrid magnetization torque motor. [ABSTRACT FROM AUTHOR]

This paper presents a 3 degrees of freedom magnetic bearing (3-DOF MB) with toroidal radial control coils. By using the toroidal coils, the proposed structure reduces the copper loss but increases the copper usage of the radial control coils. The variation is mainly related to the stator length, pole width, and yoke width. The overall structure is symmetrical about the radial stator in the axial direction, and the cross-coupling effect between the radial and axial directions can be restrained. A magnetic circuit (MC) model is built to design the structure parameters. The force characteristics calculated by the MC model and 3-D finite-element method (FEM) verify the rationality of the design. The influence of the control currents and displacements of other directions on the force characteristics are analyzed by the 3-D FEM, and the weak cross-coupling effect of the proposed 3-DOF MB is confirmed. The accuracy of the MC model and 3-D FEM is validated by the prototype experiments. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate the influence of winding location on back electromotive force (EMF) and armature inductance in flux-switching permanent-magnet (FSPM) machines. To obtain an analytical solution, a double-stator-pitch model is built based on the equivalent magnetic circuit method. Then, the open-circuit characteristics in FSPM machines with different winding layouts are analyzed by both the analytical model and finite-element-analysis method. The analysis reveals that winding inductance is easier influenced by the winding location than the permanent-magnet flux linkage and corresponding back EMF. Finally, the analytical and finite-element predictions are verified by experimental results. [ABSTRACT FROM AUTHOR]

For reaching very high magnetic fields in fully superconducting magnets, beyond 16 T for particle accelerators dipoles and beyond 23 T for solenoids, the use of high-temperature superconductors (HTS) is unavoidable. Due to the high minimum quench energy in HTS these coils are much more difficult to protect against quenches using conventional methods, such as quench heaters or coupling loss induced quench (CLIQ). Although it is possible to use a dump resistor on a short HTS magnet, extracting the energy externally, this does not provide a solution for longer magnets or magnets operated in a string, because the extraction voltage becomes unacceptably high. Here, a method named E3SPreSSO (External Energy Extraction Symbiotic Protection System for Series Operation) is proposed that allows for fast energy extraction in HTS magnets. The E3SPreSSO comprises of units with a near-zero self-inductance superconducting circuit, connected in series with the main magnet. When the protection is triggered, these devices are turned resistive, using quench heaters, overcurrent or CLIQ, causing them to absorb the energy of the system. The units can be located outside the main magnet and do not generate magnetic field. Therefore, it is possible to use relatively cost-efficient and robust Nb–Ti or possibly MgB $_2$ (at higher temperatures). This paper introduces the concept and provides an analytical method weighing the different options for designing the E3SPreSSO units themselves. [ABSTRACT FROM AUTHOR]

In this paper, a position estimation method is proposed to accurately measure the rotor position of a switched reluctance motor equipped with embedded sensing coils under both unsaturated and saturated conditions. This method effectively solves three key problems existing in traditional methods based on embedded sensing coils, which are the mutual induced voltage effect, the main magnetic circuit saturation effect, and low accuracy of the rotational speed estimation in near-zero-speed regions. To address the first problem, the sensing coils are connected into a special designed structure. Then, the sensing coil inductance, which varies with the rotor position, is encoded by some voltage signals. After that, a novel hybrid harmonic filtering algorithm based on a delay filter and a coordinate transformation is proposed to remove the dc, even harmonic, and 3nth harmonic components of the demodulated voltage signals, according to which the rotor position can be estimated continuously and accurately. By applying this hybrid harmonic filter, the main magnetic circuit saturation effect on the position estimation has been indirectly avoided. To solve the third problem, a starting algorithm based on the voltage thresholds is proposed, and a rotational speed estimation method is developed. Detailed experimental results are provided to verify the validity of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper compares the performance of inner-only and inner–outer type of magnetizing fixture designs to achieve the radial magnetization profile in an isotropic-bonded neo magnet. In inner-only fixture, the magnetization coils are located on only one side of the magnet circumference, and inner–outer fixture uses magnetization coils on either side of the magnet circumference. For both fixtures, the finite-element analysis (FEA)-based performance is presented and compared with the experimental validation. The effect of misalignment between the inner and outer coils in an inner–outer fixture is discussed using the FEA as well as experimental results, and a limit on the misalignment angle resulting in negligible reduction in mid-air-gap flux density integral per pole is arrived at. [ABSTRACT FROM AUTHOR]

Recently, image quality deteriorations due to vibrations have become a problem in an autonomous system. A lens-unit-swing (LUS) system which consists of a lens and an imaging device is a kind of image stabilization technologies that generate an inverse motion against camera shakes. The LUS system can correct an image from camera shakes over wide rotation ranges around three axes. On the other hand, this system has some problems such as an increase in size and weight. In order to solve these problems, we proposed a novel three-degree-of-freedom electromagnetic actuator for image stabilization (3D-EAIS). In this paper, we propose a dynamic modeling method for the 3D-EAIS. A state equation of the 3D-EAIS is derived. The dynamic analysis results using the derived state equation and an electromagnetic field analysis using the 3-D finite-element method are compared, and the validity of the derived state equation is investigated. Moreover, the attitude stabilization system using a sliding mode control is constructed based on the derived state equation. The disturbance response of the stabilization control system is calculated, and the effectiveness of the control system is verified. [ABSTRACT FROM AUTHOR]

In this paper, a pulsed magnetic field system developed for biological applications is presented. The proposed pulsed power setup generates repetitive controlled frequency and width square wave 0–4 kV electrical pulses and supports currents up to 1000 A. As a load, a solenoid-type inductor is used with integrated plastic cuvette for biological cells. Homogeneous repetitive microsecond range pulsed magnetic field up to 15 T inside the effective volume of the cuvette can be generated. The development process, the structure of the pulsed magnetic field setup, and the solutions implemented to achieve biomedical applicability are overviewed in this paper. The presented experimental results showing contactless permeabilization of biological cells in pulsed magnetic field have an excellent potential for the development of a new biomedical treatment technique and applicability of the setup. [ABSTRACT FROM AUTHOR]

Flux-weakening capability of permanent-magnet synchronous machines (PMSMs) is fundamentally determined by d- and q -axis inductances. Based on axial flux permanent-magnet machines (AFPMs), this paper extracts the intrinsic factors that influence the d- and q-axis inductances of PMSMs, meanwhile revealing the fact that the d- and q-axis inductances of fractional slot concentrated winding machines are not inevitably larger than that of distributed ones. The proportion of each of the d- and q-axis component inductances for multigap AFPMs is first studied. By analyzing armature inductance in conjunction with differential leakage inductance, this paper introduces a novel parameter to decouple the influence of slot-pole combinations and physical dimensions so that the “inductance ability” of different slot-pole combinations can be quantified. An improved method of calculating the slot leakage inductance of semiclosed slots is then put forward, which proves to be more accurate than the conventional method. The investigations and conclusion in this paper are not restricted to AFPMs but applicable to radial flux permanent-magnet machines as well. Validations of various slot-pole combinations are carried out with finite-element analysis and experiments. [ABSTRACT FROM PUBLISHER]

In general, a magnetic flux leakage (MFL) pipeline inspection gauge (PIG) has been applied to nondestructive testing for investigating ferromagnetic materials, such as underground gas pipelines. Although MFL PIG is efficient to the inter-city large-scale pipelines, it is hard to apply to small-size pipelines that are usually installed in the city, because the permanent magnet for MFL PIG is too big and heavy to operate inside the small pipe. The strong adhesive magnetic force of permanent magnet to the pipe wall also prevents the usage of MFL PIG in small pipelines. In this paper, we propose a new technology of nondestructive inspection by using a differential coil, which is easy to be manufactured with lightweight, low cost, and simple structure for operating inside the underground pipelines. Comparing with the conventional permanent-magnet MFL PIG, the results of the proposed system could also maximize the detection sensitivity of defect signals and minimize the magnetic adhesive force on the pipe wall simultaneously. [ABSTRACT FROM AUTHOR]

The rotary type electromagnetic actuator is often used in the electromagnetic mechanical components design, such as high-sensibility switch, signal electromagnetic relay, and so on. This type of actuator is required to have high conversion speed and action frequency, high signal reliability, and low power consumption per volume. In this paper, a new type of rotary electromagnetic actuator with permanent magnet (PM) is designed. Based on the polarity characteristics of PM, a couple of coils are designed in diagonal direction. A flux guide path is designed to optimize the magnetic circuit. PM is applied as the armature, and the electromagnetic system and the contact system are designed individually, which can achieve a high level maximum space utilization. In order to study the characteristic of PM, the PM is divided into several subsections. The migration analysis of the working point based on analytic model is carried on for the selection of PM, and the precise static characteristics of the actuator are analyzed by the finite-element model. The prototype actuator is assembled and tested, and the advantages of fast conversion speed and high reliability is verified by the test. [ABSTRACT FROM AUTHOR]

Severe leakage flux is a long-existed drawback in the transverse-flux permanent magnet machines (TFPMs), which results in a low permanent magnet (PM) utilization rate and prominent cogging torque in TFPMs. Aiming to solve this problem, this paper presents a novel consequent-pole transverse-flux machine (CP-TFM). The key is to artificially shift the upper and lower salient-pole rotors with a half-pole pitch and connect them with a ring-shaped core. Therefore, a complementary magnetic circuit is constructed to reduce the flux leakage between the adjacent poles as well as improve the PM utilization rate. To verify the feasibility of design, a 3-D finite-element model is established and its electromagnetic performance is evaluated. With the same peripheral dimension and copper loss, a quantitative comparison is carried out between the proposed CP-TFM and conventional TFPM. Finite-element simulation results reveal that compared to its contrast, the proposed solution can almost double the PM utilization ratio and effectively reduce the cogging torque. [ABSTRACT FROM AUTHOR]

The application of fault current limiter is an effective method to limit fault current. The saturated-core fault current limiter (SFCL) is one of the promising devices. However, its commercialization is limited by the high demands for the ferromagnetic material and the dc source generating magneto motive force. This paper proposes a novel three-phase compact SFCL (CSFCL) in which a common core and a permanent magnet are used to solve the mentioned challenges. The common core can significantly reduce the amount of required ferromagnetic material. The basic operating principle of CSFCL is introduced based on the analysis of the CSFCL’s magnetic circuit and equivalent electrical circuit. Finite-element analysis (FEA) simulations were performed by ANSOFT to validate the effectiveness of the CSFCL’s fault clipping performance. [ABSTRACT FROM AUTHOR]

Compared with dc magnetic bearings, an ac magnetic bearing has obvious advantages in cost savings and reducing power consumption. For more precise control of the ac magnetic bearing, it is particularly important to build a correct mathematical model of radial suspension forces. Due to the working principle of the ac magnetic bearing, it has similarities to the suspension subsystem of a bearingless motor, thus the modeling method for radial suspension forces of the bearingless motor could be referenced for modeling the radial suspension forces of the ac magnetic bearing. This paper presents a new modeling method based on the Maxwell tensor method for radial suspension forces of the ac magnetic bearing. Compared with existing methods, the invention method designed specially for the ac magnetic bearing overcomes inaccuracy and possesses advantages of directness and universality. Taking the ac hybrid magnetic bearing (ac HMB), for example, this paper presents the mathematical modeling process of radial suspension forces with the proposed method. The comparison result between the models established by the equivalent magnetic circuit method (the most classical modeling method for magnetic bearings currently) and by the proposed method shows the high uniformity in their forms of expression (the only difference is the coefficient between them). Being different from the traditional modeling method, we do not need the detailed derivation and complex theoretical computation based on the particular magnetic circuit analysis for this particular case but simply modify several key expressions representing magnetic circuit features in the modeling process with this method. Therefore, the proposed method invented especially for the ac magnetic bearing has the greater advantage of directness and universality than previous modeling method. To illustrate the precision of the proposed modeling approach, the verification experiment is designed and the encouraging experimental results show that the model based on the Maxwell tensor method is more close to the test results comparing with equivalent magnetic circuit method. Thus, the proposed modeling method makes the modeling results on radial suspension forces of the ac magnetic bearing more accurate, universal, and direct. [ABSTRACT FROM PUBLISHER]

Improving frequency response of direct drive valve (DDV) system is a research focus on the hydraulic system. This paper presents a high-frequency response DDV system based on voice coil motor (VCM-DDV). First, a new design of VCM with high acceleration is proposed. A magnetic circuit method and electromagnetic finite element method are adopted in this paper. A 3-D thermal field element method is also employed to analyze the temperature rise of the developed VCM at rated current. Next, a dual closed-loop control structure is applied in the developed VCM-DDV system. Moreover, a nonlinear PID control strategy is proposed to resolve the contradiction between stability and rapidity. The results of performance test indicate that the acceleration of the developed VCM is evidently improved, and it reaches 306 times of gravity acceleration. Experimental investigation indicates that the developed VCM-DDV system has excellent static and dynamic performances. The position bandwidth of the developed VCM-DDV is capable of achieving 350 Hz. [ABSTRACT FROM AUTHOR]

A recently proposed magnetic structure called Tripolar Pad (TPP) is investigated as a primary pad in an inductive power transfer battery charging system for electric vehicles. In this paper, a TPP primary is evaluated for 3.3 kW power transfer to both a circular pad and a bipolar pad as secondary pads. A mathematical model is presented to describe the power transfer from the TPP primary to the secondary pads then a control scheme is proposed which exploits the mutual decoupling between the TPP coils to find optimal primary currents. The optimization of the primary currents in the TPP improved the effective coupling factor over traditional topologies, particularly when the secondary was misaligned, and maintained leakage magnetic flux below International Commission on Non-Ionizing Radiation Protection guidelines. The result for the proposed TPP is validated with practical measurements. [ABSTRACT FROM AUTHOR]

A good magnetic design of a wireless electric vehicle (EV) charging system requires accurate characterization of the equivalent circuit parameters. This is while considering the effect of the magnetic core and the conductive shielding layers. In the literature, such an analysis is done using 3-D finite element analysis, which makes the design and optimization process time-consuming and computationally expensive. In this paper, an integrated analytical model for the characterization of a circular wireless power transfer EV pads is utilized. This analytical model provides a valuable tool to optimize the design process. This model is utilized when evaluating the objective function for each individual in the multiobjective Pareto Optimality optimization algorithm. The objective is optimizing the pads with three decision variables and four constraints. [ABSTRACT FROM AUTHOR]

A saturated core fault current limiter (FCL) essentially utilizes the dynamic and nonlinear magnetic behavior of steel cores to operate as a variable reactor. However, the nonlinear characteristic of magnetic materials has made modeling this unique device a difficult task. Hence, experimental measurements and finite-element method (FEM) analysis are the most common techniques used to characterize the transient behavior of the device. Both of these techniques, while accurate, cannot be used to analyze the transient electrical behaviour of FCLs in complex power systems, particularly when investigating power system switchgear behavior during fault events. FEM-based FCL modelling, despite its usefulness as a design verification tool, cannot be easily coupled to all electromagnetic transient programs that are in use today. This paper presents two modeling approaches to represent the saturated core FCL in transient network simulators: 1) the nonlinear reluctance model and 2) the nonlinear inductance model. Both models are implemented in pscad/emtdc and are validated by experimental results of a single-phase prototype saturated core FCL, where excellent agreement between the experimental and the modelling approaches is achieved. [ABSTRACT FROM PUBLISHER]

Superconducting linear accelerators include a superconducting magnet system for particle beam transportation that provides beam focusing and steering. This system consists of a large number of quadrupole magnets and dipole correctors mounted inside or between cryomodules with SCRF cavities. Each magnet has current leads and is powered from its own power supply. The paper proposes a novel approach to magnet powering based on using superconducting persistent current switches. A group of magnets is powered by the same power supply through the common, for the group of cryomodules, electrical bus, and pair of current leads. Superconducting switches direct the current to the chosen magnet and close the circuit, providing the magnet operation in a persistent current mode. Two persistent current switches were fabricated and tested. The paper also presents the results of magnetic field simulations, decay time constants analysis, and a way of improving quadrupole magnetic center stability. Such an approach substantially reduces the magnet system cost and increases the reliability. [ABSTRACT FROM PUBLISHER]

This paper is the final paper in a series of papers that discusses passive quench protection for high inductance solenoid magnets. This report describes how passive quench protection system may be applied to superconducting magnets that are connected in series but not inductively coupled. Previous papers have discussed the role of magnet sub-division and quench back from a conductive mandrel in reducing the hot-spot temperature and the peak coil voltages to ground. When magnets are connected in series, quench-back from a conductive mandrel can cause other magnets in a string to quench even without inductive coupling between magnets. The magnet mandrels must be well coupled to the magnet circuit that is being quenched. When magnet circuit sub-division is employed to reduce the voltages-to-ground within magnets, the resistance across the subdivision becomes the most important factor in the successful quenching of the magnet string. [ABSTRACT FROM AUTHOR]

A superconducting property measurement system (SPMS) is used to acquire electrical and thermal properties of short HTS tape samples. The SPMS is composed of a specimen holder for mounting an HTS tape and magnet for applying a magnetic field externally. The magnet consists of two split racetrack windings and is designed to produce maximum 3 T of center field at 20 K. In this paper, an HTS magnet for the SPMS cooled by a cryocooler was designed. A HTS magnet consists of several pancakes winding wound from YBCO CC tape. We report out design for a conduction-cooled magnet using YBCO CC tape. For varying the number of double pancake coils (DPCs) and the bending radius, an electromagnetic field analysis is used. We subsequently find a suitable HTS magnet type for an SPMS. This paper describes the quench protection system for an HTS magnet of the SPMS. The detection of any normal zone must be preceded to protect the HTS magnet. We use simulated protection circuit to estimate the trigger conditions. The presented results in this paper will be verified using fabricated protection circuit. [ABSTRACT FROM AUTHOR]

This paper proposes and implements a new single-phase magnetless flux switching machine (FSM) for rooftop wind power generation. The key is to integrate an outer-rotor FSM and an inner-rotor FSM with shared stator yoke and stator drum windings. In such a way, this proposed machine can not only realize flux switching function to regulate magnetic flux effectively, but also incorporate the field and armature windings within one stator to reduce the copper losses and improve the overall machine efficiency. Meanwhile, the structure is compact and rotors can be directly driven by blades to capture the wind power. The machine design guidelines from both magnetic and electric aspects are illustrated, the machine characteristics are analyzed by using time-stepping finite-element method, and the system performances are evaluated based on mathematical modeling. Both simulation and prototyping test are conducted to verify the validity of the proposed machine and system. [ABSTRACT FROM AUTHOR]

Permanent magnets have long been known to store magnetic energy in the alignment of the magnetic domains within the material. This paper investigates the possibility of constructing a magnetic device that can effectively extract the stored potential energy from permanent magnets and convert that energy into electrical energy. The concept stemmed from a number of patents that claimed to effectively extract energy from strong neodymium or samarium cobalt magnets on a macroscopic scale using specially designed magnetic flux paths. Their method uses one of several different techniques to switch permanent magnet flux between alternating paths and electrical energy is extracted from coils intercepting this flux as it changes within the core. Using experimental testing, magnetic simulations, and theoretical predictions, our research examined this question. The experimental results indicate that the devices tested do not effectively extract magnetic energy from the magnetized materials under test, indicating that the design is not suitable for use as a magnetic battery. [ABSTRACT FROM AUTHOR]

The aim of this paper is to simulate the performances of a ground fault circuit-breaker (GFCB) relay with new low-nickel-content alloys. Indeed, in the construction industry, the materials become more expensive as their nickel content increases. Moreover, the demand for nickel is particularly sensitive to the economic conjuncture. Therefore, an original electromagnetic relay model has been developed and validated in different working conditions (current amplitude, frequency, and temperature). A dedicated magnetic characterization of materials is needed, using basically a usual and industrial GFCB relay for reference and design data in modeling. First, the magnetic model of the relay is built and checked against experimental data. The simulation may predict the tripping current threshold of the relay. On the other hand, new low-nickel-content alloys for relay parts are studied in this framework, thanks to the developed model. The effects of temperature on the magnetic properties of the candidate materials and the electrical performances of the virtual relays are presented. The results, analysis, and conclusions are given. Finally, a first attempt to predict the economic gain obtained with a change of material is made. [ABSTRACT FROM AUTHOR]

Leakage inductance is one of the most important aspects of transformer design. Herein, the calculation of the leakage inductance of core-type tape-wound transformers is considered in the context of a magnetic equivalent circuit-based analysis used to support optimization-based design. In optimization-based design, numerical efficiency is critical since 105–106 evaluations may be conducted. Thus, this paper presents a computationally efficient method to compute leakage inductances. The method is based on analytical calculation of the field intensity using Ampere's law in the noncore regions of the devices. The predictions of the proposed method are shown to be more consistent with the predictions of a 3-D finite-element analysis than other documented approaches. [ABSTRACT FROM AUTHOR]

Linear machines are currently considered as viable candidates for direct-drive wave and free-piston energy converters. This paper is devoted to an approach based on a magnetic equivalent circuit (MEC), which is also called lumped circuit, dedicated to the modeling and sizing of a tubular linear permanent-magnet synchronous machine (T-LPMSM). The proposed approach considers, in a first step, the cancelation of the end-effect phenomenon. To do so, a dedicated design procedure, consisting in 1) achieving a $2\pi/3$-shift between the armature phase flux linkages by selecting a fractional ratio of the stator pole pitch to the mover one and 2) balancing the amplitudes of the phase flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions, is firmly applied on two basic T-LPMSM topologies using a dedicated MEC. Then, an investigation of the influent sizing parameters on the force production capability of the initial concept is carried out. The MEC-based prediction of the force requires the incorporation of the mover displacement, yielding the so-called “position varying MEC” on one hand and the armature magnetic reaction on the other hand. The finite-element analysis of the armature phase flux linkages and the developed force enable the validation of the results yielded by the established MECs. [ABSTRACT FROM AUTHOR]

This paper presents a new topology of parallel hybrid excitation machine (PHEM), which integrates permanent-magnet synchronous motor (PMSM) and variable-reluctance machine, namely, doubly salient electromagnetic machine (DSEM), and provides a solution to better field-regulating capability. The configuration and the operation principle of the proposed PHEM are introduced. The combination criterion and design consideration are discussed. The performances of the two axial sections (PMSM and DSEM) are studied by 2-D finite-element analysis (FEA), respectively, to achieve reasonable integration. The field and voltage regulation capability of the PHEM is further investigated by 3-D FEA. A prototype PHEM is designed, manufactured, and tested. The measured results verify structural validity and finite-element predictions. The loss is predicted, and the measurement of short-circuit current illustrates the capacity of deexcitation at fault. The results confirm that the PHEM achieves effective power superposition of two different brushless machines. Bidirectional field-regulating capability facilitates a wide field regulating range of 6.5:1 under no load. [ABSTRACT FROM PUBLISHER]

This paper presents a hybrid approach coupling natural element method (NEM) and boundary element method (BEM) for the treatment of unbounded problems. The goal is to combine the accuracy of the NEM and ability of the BEM in modeling linear and deformable domains without a mesh. The performance of the proposed scheme is compared with a finite-element method-BEM coupling in terms of accuracy. Results show that for a given number of degrees of freedom, the proposed approach (NEM-BEM) is able to provide more accurate solutions. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

This paper presents an enhancement of high spacial resolution magnetic probe for the applications of measuring magnetic fields emitted from cryptography micro-electronic devices. The on-chip sensing system includes a magnetic pick-up coil, three-stage low-noise amplifier, mixer, and low-pass filter. Noise problems are reduced by the proposal of using the down-conversion mixer. A two-step removal of Si-substrate (Si-SUBS) areas is also proposed by applying a focused-ion-beam process to avoid eddy currents that reduces the coil sensitivity. Four probe chips are fabricated in a 0.18 \mu m CMOS five-metal layer process with different coil sizes and with/without Si-SUBS removals. Experimental results on a thin wire and micro-strip line show the proposed system achieves high spacial resolution and sensitivity for near-field magnetic scanning. [ABSTRACT FROM AUTHOR]

This paper introduces the development of an analytical mathematical model to describe the fast dynamic response ofthe opening and closing mechanism of a power line recloser switch. The model is then used to simulate and evaluate thetransient mechanical and electromagnetic performance during the opening and closing movements of the recloser. Thesimulated results are validated by measurements on an actual recloser while it operates. This model can be used tooptimize the recloser design and reduce the manufacturing cost, instead of using the time-consuming finite-elementanalysis. [ABSTRACT FROM AUTHOR]

In magnetic resonant coupling wireless power transfer (WPT) system, the frequency splitting phenomena have a vital influence on the output power. This paper mainly focuses on the frequency splitting of two-coil and three-coil WPT. First, the frequency characteristics of transfer power and system efficiency of the two-coil WPT are analyzed by circuit theory. In addition, the magnetic field distribution of the two splitting frequencies is simulated to analyze which frequency is better for the operating frequency. Second, considering the reference resistance of RF power, the frequency splitting of two-coil and three-coil WPT is analyzed. Finally, the critical coupling, which determines the over coupled region, of two-coil and three-coil WPT is derived. Meanwhile, we propose a tuned frequency method according to the numerical results. In addition, the transfer power can be kept at a relatively constant level in the over coupled region. [ABSTRACT FROM AUTHOR]

This paper presents a novel multiphase permanent-magnet (PM) synchronous machinery series adopting two adjacent coils per phase and modular stator. Machine design principles, including modular stator design, segmental interior PM-assisted rotor design, and winding factor improvement, are investigated. Moreover, analytical modeling of winding inductance is developed to provide insights into the magnetic circuit of this type of machine. The proposed machinery series is suitable for wheel-driving electric vehicles attributing to their high magnetic isolation feature, good flux-weakening capability, and feasibility of modular fabrication. [ABSTRACT FROM AUTHOR]

This paper describes a novel approach to designing a high-current magnetic field generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. Challenges for robust and practical design are introduced. A few of the main possible solutions for designing versatile and powerful pulses are introduced and discussed. Finally, future improvement in functionality of the HCMFG is proposed. [ABSTRACT FROM AUTHOR]

This paper presents an empirical approach of flux flow loss in a high-temperature superconducting (HTS) magnetic energy storage coil based on finite element algorithm and numerical circuit analyses. The critical current and flux flow loss distributions are discussed in details by integrating the magnetic-field-dependent anisotropy and powerlaw critical state model of first-generation HTS Bi-2223 tape. A coil-current-dependent power-law formula is derived to estimate flux flow loss of a prototype Bi-2223 solenoid coil under different energy exchange operation conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel slotless limited-angle torque motor (LATM) for reaction wheels torque measurement system. The proposed slotless LATM has a uniform torque profile during its operating range, constant torque coefficient owing to avoiding saturation in back iron core. The slotless LATM has been designed and optimized using both magnetic circuit method and 2-D FE method. A scheme of magnetic pole spliced by three segments is proposed to improve flat width of air-gap flux density and torque performance. Finally, a prototype machine is established and its experimental results are presented and discussed. The theoretical and numerical results are validated with the experiments in the same operating conditions. [ABSTRACT FROM AUTHOR]

To realize the basic technology of a package-level dc power grid for the next generation power delivery to large scale integrated circuits (LSIs), two types of planar spiral inductors embedded in an organic interposer, for several tens of megahertz switching power supply integrated in LSI package, have been proposed. One is a Zn–Fe ferrite core spiral inductor, and another is a hybrid core spiral inductor, with quasi closed magnetic circuit consisting of the bottom Zn–Fe ferrite core and top carbonyl-iron/epoxy composite core. In this paper, the two types of planar spiral inductors have been fabricated and evaluated. From the experimental results, it was found that the hybrid core planar spiral inductor exhibited higher \(Q\) -factor and larger rating dc current than the Zn–Fe ferrite core inductor. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a transverse-flux-type cylindrical linear synchronous motor using generic armature cores for rotary machinery that can address the problem of complex structures in conventional transverse-fluxtype topologies. First, the operational principle and structural advantages of the proposed model are explained. The thrust density and cogging force are investigated during the initial design stage using an application in which large thrust density and low cogging force are required. The proposed model is both theoretically and numerically designed by using a magnetic-circuit method and a 3-D finite-element method, respectively. Finally, the results and efficacy of our structural concept are experimentally validated. [ABSTRACT FROM PUBLISHER]

The design of control strategies for permanent magnet synchronous machines (PSM) is almost exclusively based on classical dq0-models. These models are, however, not able to systematically describe saturation or nonhomogenous air gap geometries typically occurring in PSM. This paper deals with a framework for the mathematical modeling of PSM based on magnetic equivalent circuits. Different to existing works, the model equations are derived by means of graph theory allowing for a systematic choice of a minimal set of state variables of the model and a systematic consideration of the electrical connection of the coils of the motor. The resulting model is calibrated and verified by means of measurement results. Finally, a magnetically linear and a dq0-model are derived and their performance is compared with the nonlinear model and measurement results. [ABSTRACT FROM AUTHOR]

We have designed and fabricated a 3-T Magnetic Resonance Imaging (MRI) magnet system for the human brain, which was wound with Bi-2223 tape conductors. The magnet was successfully energized to 1.5 T and then up to 3.0 T. The magnet experienced more than 60 ramp-up and down processes to 1.5 T with no trouble. A magnetic field of 3.0 T (184.8 A) could be maintained for longer than 3 h without any problems. However, abnormal voltage behavior was observed during the ramp down for the third trial to 3.0 T, and the temperature rapidly increased with a ramping rate of 1.7 K/min. To investigate the cause, we opened the cryostat and inspected the inside of the magnet. In addition, we have analyzed the details of this event using the recorded current, voltage, and temperature data. The purpose of this paper is to report the investigation of this abnormal event in the magnet. [ABSTRACT FROM PUBLISHER]

Future applications of wireless power transfer will include powering various devices in a room, charging electric vehicles in a parking area, charging moving robots, and so on. Therefore, practical wireless power transfer must be able to support complicated configurations, for example, combination of multireceiver and repeaters. Many past works have discussed methods for improving efficiency and, more recently, extended the methods to multireceiver systems. However, controllable power division among receivers is also an important feature as receivers nearer to the transmitter tend to absorb more power compared to further ones. In this paper, a new impedance matching and power division method utilizing impedance inverters only at the receiver sides is proposed. The mathematical equations in the proposed method are then generalized for arbitrary number of receivers and arbitrary number of repeaters. [ABSTRACT FROM PUBLISHER]

Permanent magnetic actuators (PMAs) have been widely used in medium-voltage vacuum circuit breakers (VCBs) due to their high reliability and controllability. However, a conventional bistable PMA cannot be adopted in power equipment for the transmission voltage level such as 126 kV VCBs directly because of its low-velocity characteristics. The objective of this paper is to propose a multimagnetic circuit PMA to satisfy the high-velocity requirements for 126 kV VCBs. The novel PMA is a bistable and axisymmetric structure, including holding and driving components whose magnetic circuits are separated. Air gaps are specifically designed in the magnetic circuits to improve the velocity performance of the novel PMA. Both static and dynamic characteristics of the novel PMA model have been calculated through finite-element software coupled with multi-body dynamics software. Furthermore, a prototype of the PMA has been developed according to the calculation results. The experimental results on the prototype have shown that the velocity characteristics of the PMA are able to meet the requirements of a 126 kV VCB and agree well with the simulation results. [ABSTRACT FROM PUBLISHER]

This paper presents: 1) a novel method for accurate high-frequency modeling of dry-type transformer windings based on magnetic and electric field simulations for parameter extraction of the detailed equivalent circuit of the entire winding system; 2) a method for fast and accurate transient solution of the circuit differential equations that describe the voltage distribution over the winding system; 3) an efficient, cheap, and nondestructive low-voltage measurement system based on a self-developed lightning-impulse generator; and 4) verification of the simulation results by comparison with measurement. [ABSTRACT FROM AUTHOR]