Magnetic Flux Characteristics Research Articles

Extended 2-D Magnetic Field Modeling of Linear Motor to Investigate the Magnetic Force Parameters of High-Speed Superconducting Maglev

A 2D numerical finite element model of a linear synchronous motor (LSM) is extended based on the magnetic field and moving mesh properties to investigate the magnetic flux and magnetic force characteristics of the high-speed EML Maglev system, by using HTS coils rather than lower current carrying copper coils on the onboard unit and PMs on the ground. In this 2D LSM model, the transient, time dependent solver is used to obtain the magnetic flux densities. Both the propulsion and levitation forces increased with increasing supercurrent J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> values indicating the advantage of using the superconducting windings in PM-LSM of Maglev vehicles as compared to the copper wires. It was also determined that although the propulsion force is obtained on a comparable level with the studies in literature, the lower levitation force issue than the EDS, despite the better propulsion to levitation force ratio, can be overcame by using the high flux trapping capacity bulk HTSs in the onboard unit together with the superconducting coils. The determined higher propulsion force in this PM-LSM Maglev model indicates that the Maglev vehicle can reach higher velocities in a short-distance and thus this vehicle can be effectively used in short-distance travels in addition to the long-distance transportation. On the other hand, since the EDS system to be accelerated in a certain time interval via conventional wheels to achieve sufficient levitation, PM-LSM system can be integrated into the EDS Maglev system to ensure higher acceleration in a short time interval in addition to the higher levitation and propulsion force performances.

Expansion of Motor High-Efficiency Area by Inserting Magnetic Composite Material into Rotor

Variable magnetic flux motors have been proposed to achieve high-efficiency operation over a wide drive range ranging from high torque to high-speed. This paper clarifies the high efficiency area expansion effect of a variable flux motor with a magnetic composite material inserted in the rotor. To achieve the effect of enlarging the maximum efficiency range, this motor uses magnetic composite materials with much lower saturation magnetic flux density and iron loss than electromagnetic steel plate. This paper reports the magnetic and mechanical properties of the magnetic composite material using Fe–Si–Al alloy, considering low iron loss. The simulation results clarified the variable magnetic flux characteristics for reducing loss at high-speed rotation by actively utilizing the magnetic saturation region of the magnetic composite material. The efficiency improvement in the high-speed region is attributed to the suppression of spatial harmonics without significantly reducing the q-axis inductance. Furthermore, the proposed motor achieves both the expansion of the high-efficiency range and relaxation of mechanical stress by increasing the thickness of the bridge part adjacent to the permanent magnet.

Experimental investigation of modified in-wheel switched reluctance motor with reduced torque ripple for electric vehicles

This research work is aimed at the modification of in-wheel switched reluctance motor (Outer rotor-type SRM) with minimized torque ripple for electric vehicles. The geometry of stator and rotor poles affects the torque. Variation in the stator and rotor pole geometry causes change in the torque profile. To reduce the torque ripple and to increase the average torque, modification in the stator and rotor pole shoes is presented in this article. The stator and rotor pole shoes with notches and projections are proposed with the objective of minimization of torque ripple and maximization of average torque. Electromagnetic analysis of conventional and modified in-wheel SRM is done with computer-aided design software MagNet 7.1.1. From the finite element analysis results, the average torque and torque ripple values are derived. Prototype of 8/6, 1000 W in-wheel SRM with the notches and projections is fabricated. Experimentation is performed on the fabricated machine to measure the magnetic flux linkage, current and speed characteristics of the proposed in-wheel SRM. The precise determination of magnetic flux characteristics is significant to check the machine design and to accurately predict the action of modified in-wheel SRM. Static modeling results of the fabricated machine were coherent with the experimental values.

Bipolar-resistive switching and memristive properties of solution-processable cobalt oxide nanoparticles

This work reports the memristive properties of solution-processable cobalt oxide nanoparticles (CoO NPs) for resistive memory application. The memristive current???voltage hysteresis loop with good bipolar-resistive switching (BRS) property was shown by the developed device. Substantiate to this, the asymmetric device charge and double-valued charge???magnetic flux characteristics were calculated from the experimental electrical data and demonstrated the existence of the non-ideal memristor properties. The CoO memristive device can switch up to 103 BRS cycles and can retain the data up to 5????????103 s. The switching uniformity of the CoO memory device was elucidated by a cumulative probability distribution and statistical calculations. The low-resistance state shows little variation whereas broad variation was observed for high-resistance state. The theoretical model fitting results suggested that the conduction in the device during high-resistance sate was due to the Schottky and space charge-limited current and Ohmic current dominated in the low-resistance state. The formation and rupture of conductive filament with the assistance of interfacial dynamic is a possible reason for BRS in the CoO NPs-based memristive device.

Improvement of Magnetic Shielding for Transformers Based on the Magnetic Flux Characteristics at Shielding Ends

Magnetic shielding is generally laid on the transformer tank and clamps to reduce the eddy current loss in the tank, yet designers did not pay attention to the phenomenon of flux concentration caused by magnetic shielding. According to the simulation results of the accustomed shielding structures, we noticed that the flux density near the end of shielding plates is relatively high. Thus, an idea is proposed that regions with lower flux density before shielding construction may also need to be shielded, and the shielding should be made to closed path or loop, i.e., the shielding plates in different directions should be connected to each other, or the end of the plates should be bent to the core surface. The aim of all these measures is to avoid the flux entering the transformer tank. The improved structure of the shielding can significantly reduce the loss of the tank, thus mitigating the extent of local overheating. As for the lower clamps, adding necessary shields can dramatically reduce the loss. Furthermore, in consideration of saving materials, adjustment on shielding geometry is performed. A final shielding design is achieved, which reduces the loss, mitigates local overheating, and saves materials. The effect of the magnetic shielding is verified by the finite-element analysis.

Electromagnetic Performances and Main Parameter Sensitivity Effect on Unbalance Magnetic Flux in a New Single-Phase FEFSM with Segmental Rotor

Three-phase field excitation flux switching motor (FEFSM) with salient rotor structure has been introduced with their advantages of rotor easy temperature elimination and controllable FEC magnetic flux. Yet, the salient rotor structure is found to lead a longer magnetic flux path between stator and rotor parts, producing a weak flux linkage along with low torque performances. Hence, a new structure of single-phase FEFSM using segmental rotor with non-overlap windings is proposed with advantages of shorter magnetic flux path, light weight and robust rotor structure. Analysis on fundamental magnetic flux characteristics, armature and FEC magnetic flux linkages, cogging torque, back-Emf, various torque capabilities, refinement of unbalance magnetic flux, and torque-power versus speed characteristics are conducted using 2D FEA through JMAG Designer version 15. The results show that magnetic flux amplitude ratio has been improved by 41.2% while the highest torque and power achieved are 1.45 Nm and 343.8 W, respectively.

Performance Optimization of a Three-Dimensional NanoSQUID Based on Niobium Tunnel Nanojunctions

We report results about an optimized three-dimensional nanoSQUID based on niobium tunnel nanojunctions having the loop suspended to reduce the parasitic capacitance. The SQUID loop has a size of 400 × 600 nm 2 while the dimension of the square tunnel nanojunctions is 150 × 150 nm 2 with a density of the critical current of about 35 × 10 3 A/cm 2 . The nanodevice has been characterized at liquid helium temperature; it has shown nonhysteretic current-voltage characteristics and smooth voltage- magnetic flux characteristics resulting in a very stable operation in a wide range of bias points. The spectral density of the magnetic flux noise in the white region, measured with a two-stage noise measurement setup, was as low as 300 nΦ 0 /Hz 1/2 corresponding to a spin sensitivity of few Bohr magnetons for bandwidth unit.

Design optimization of a novel elastomeric baffle magnetorheological fluid device

This article details the design optimization of a novel magnetorheological fluid device, which incorporates a rolling elastomeric baffle to contain the fluid and minimize cost and complexity. The application considered here is an electronic joystick for a drive-by-wire construction machine, although designs for other semi-active applications could be similarly optimized. Performance is evaluated computationally and experimentally. A computationally efficient system model is developed and validated using finite element analysis to accurately predict the device’s magnetic flux characteristics. The design methodology is based on a variant of the firefly algorithm, which identifies promising initial designs, and conjugate gradient methods, which optimize these designs. A unique graphical method for interpreting the results of population-based firefly optimization is demonstrated. An experimental prototype, based on the optimized design, is tested and its data compared to simulation results.

Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects

Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models, however this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and properties from the Helio- spheric Imagers onboard the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From the main HICAT catalogue of over 2,000 CME detections, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active region (AR) sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with AR magnetic field properties, such as magnetic flux, area, and neutral line characteristics. The resulting LOWCAT catalogue is also compared to the extensive AR property database created by the EU Horizon 2020 FLARECAST project, which provides more complex magnetic field parameters derived from vector magnetograms. Initial statistical analysis has been undertaken on the new data to provide insight into the link between flare and CME events, and characteristics of eruptive ARs. Warning thresholds determined from analysis of the evolution of these parameters is shown to be a useful output for operational space weather purposes. Parameters of particular interest for further analysis include total unsigned flux, vertical current, and current helicity. The automated method developed to create the LOWCAT catalogue may also be useful for future efforts to develop operational CME forecasting.

Study on a Maximum Torque Control of Magnetic-Geared Motors

Traction motors of EVs require wide power band characteristics. A magnetic-geared motor has a possibility to achieve these requirements because it has passively variable magnetic flux characteristics. In this paper, the passively variable magnetic flux characteristics of the magnetic-geared motor is investigated using finite element analyses. Furthermore, a maximum torque control method for the magnetic-geared motor is proposed and investigated.

Evaluation of mechanical properties in medium carbon steel with a point mode electromagnetic sensor

This paper reports the evaluation of mechanical properties of medium carbon steel based on a novel sensor. The novel point mode electromagnetic sensor with compact configuration and concentrated magnetic flux characteristics has attracted wide attention in recent years. The point mode electromagnetic sensor consists of exciting coil, receiving coil and needle permalloy core embedded into the coil. Response surface methodology was adopted to explore the relationships between the structure paramerters of core (contact radius and height of the cone) and magnetic field intensity based on finite element analysis. The analysis results showed that the contact radius and cone height of the core had important influences on magnetic field intensity. The influence of the cone height was lesser than that of the contact radius. Moreover, the mathematic model was verified effectively by testing magnetic field intensity of different cores based on scanning techniques. Mechanical properties experiment results measured by using a novel sensor showed that a linear correlation exists between the values of amplitude for fundamental and the hardness of samples.

Thrust Characteristics Improvement of a Circular Shaft Motor for Direct-Drive Applications

This paper presents a semicircular tubular linear machine model, which is called a circular shaft motor (CSM), with trapezoidal magnets. For a conventional CSM system, the stator is difficult to construct as designed, and the thrust characteristics are not high enough. The proposed CSM model includes trapezoidal magnets that are magnetized in the axial direction. This structure can facilitate the construction of the stator and decrease the thrust ripple. In addition, the magnetic flux characteristics are shown as new results of a CSM. Magnetic field is related to thrust characteristics closely. By investigating magnetic distribution characteristics, it is shown that the proposed model can improve magnetic field characteristics. In this paper, the structure of the proposed CSM model is described. The improvement in the thrust characteristics is verified by magnetic field analysis. The thrust characteristics of the proposed CSM system are verified in a thrust characteristics test. The magnetic flux characteristics of the proposed CSM system are compared with those of a conventional CSM system to evaluate the thrust characteristics.

Improved Design of Three Phase Hybrid Excitation Flux Switching Motor with Segmental Rotor

This paper presents the new design of Hybrid Excitation Flux Switching Motor (HEFSM) using segmental rotor structure. HEFSMs are those that consist all the excitation flux sources at their stator with robust rotor structure. The rotor is designed as segmental due to the reason that segmental rotor has ability to yield the magnetic path for conveying the field flux to nearby stator armature coil with respect to the rotation of the rotor. This design gives the clear advantage of shorter end winding compared to the toothed rotor as there is no overlap winding between field excitation coil (FEC) and armature coil. In this paper the initial design of HEFSM with segmental rotor has been improved by changing segment span, FEC slot area and armature slot area until maximum torque and power of 33.633 Nm and 8.17 KW respectively have been achieved. Moreover coil test analysis, induced voltage, cogging torque, magnetic flux characteristics, torque vs. field current density and torque vs. power speed characteristics are examined on the basis of 2-D finite element analysis (FEA).

Improved PMSM model considering flux characteristics for model predictive‐based current control

Model predictive‐based current control, which was proposed in our previous study, offers better current response performance by employing mathematical models of an inverter and a permanent magnet synchronous motor (PMSM). The performance of this kind of approach depends on the predictive model. From a more practical point of view, current behavior in the steady state should be improved. In our previous model predictive‐based current control, the inverter model was refined by taking the dead‐time into consideration. The use of the refined inverter model reduces the current offset in the control. However, the PMSM model was not investigated.This paper proposes a more appropriate PMSM model for model predictive‐based current control in order to improve the current prediction in the steady state. For the purpose, we incorporate more detailed magnetic flux characteristics instead of average characteristics into the improved PMSM model. Specifically, in the improved PMSM model, the inductance of the PMSM is divided into transient and steady‐state parts on the basis of magnetic saturation. The effectiveness of the improved model in the model predictive‐based current control is demonstrated through simulations and experiments. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Performances of niobium planar nanointerferometers as a function of the temperature: a comparative study

The growing interest in the development of nano-superconducting quantum interference devices (nanoSQUIDs) and their applications in nanoscience demands a deep study of these ultra-high-sensitivity nanodevices. In this paper, the main features of niobium planar nanointerferometers as a function of the temperature have been investigated. In particular, two types of nanodevices have been realized and studied: one based on nanobridges and the other on sub-micron Josephson tunnel junctions (JTJs). The nanobridge-based nanointerferometer, fabricated by electron beam lithography (EBL), consists of a sub-micrometric loop (effective area of 0.5 μm2), interrupted by two Dayem nanobridges having a width and length of 50 and 80 nm respectively. The JTJs-based nanointerferometer has two Nb/Al-AlOx/Nb SNIS (superconductor/normal-insulator/superconductor) junctions with an area of 0.09 μm2, connected by a rectangular loop (1 μm × 0.2 μm), and realized by the three-dimensional focused ion beam (3D FIB) sculpting technique. For both nanodevices, measurements of current–voltage characteristics and critical current versus external magnetic flux have been performed at operating temperatures ranging from 4.2 to 1.2 K. The critical current modulation depths, magnetic flux to current transfer factor (current responsivity) and magnetic flux resolution as a function of the temperature have been evaluated for both nanosensors. Furthermore, measurements of the voltage–magnetic flux characteristics and the spectral density of magnetic flux noise have been performed at T = 4.2 K.

Hysteretic NanoSQUID Sensors for Investigation of Iron Oxide Nanoparticles

Magnetic nanosensors based on niobium nano superconducting quantum interference device (nanoSQUID) have been fabricated and employed to investigate the magnetic properties of iron oxide nanoparticles. The nanoSQUIDs, fabricated by electron beam lithography, consist in a square loop interrupted by two nanometric constrictions (Dayem bridges). The flux capture area is 0.5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while the Dayem nanobridges have a width and a length ranging from 50 to 90 nm and 70 to 80 nm, respectively. Measurements of current to voltage (I-V) and critical current to magnetic flux (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> -Φ) characteristics have been reported for different nanobridge dimensions. At T = 4.2 K the nanosensors have shown a hysteretic I-V characteristic and a triangular shaped I-Φ pattern suggesting a strong deviation from sinusoidal current-phase relationship. Due to the hysteretic behavior, the devices have been employed as a magnetic flux to current transducer. In such a configuration an overall magnetic flux resolution of about 0.3 mΦ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> has been estimated. These nanosensors have been successfully employed to measure the field dependence and the time relaxation of the magnetization of iron oxide nanoparticles having a mean diameter of 4.2 nm. The experimental curves undoubtedly prove that the nanoSQUIDs reported here can be successfully employed to investigate the magnetic properties of very small nanoparticles.

Experimental Analysis of the Magnetic Flux Characteristics of Saturated Core Fault Current Limiters

A fault current limiter (FCL) is a device that is designed to reduce the impact of fault currents on electricity networks and increase the availability of such networks to consumers. One particular FCL technology that is currently attracting worldwide attention, from both researchers and commercial engineering companies, is the saturated core FCL. This device utilizes the change in permeability between the saturated and unsaturated states of a magnetic core to provide both low steady state losses and effective fault current limiting. Typically the core is saturated using an electromagnetic coil, which can be either superconducting or non-superconducting. Although there have been several studies on the electrical characteristics of this device, the transient magnetic behavior has been largely overlooked. In this paper the magnetic flux characteristics of saturated core FCLs are experimentally analyzed. The study includes the magnetic behavior during both the initial biasing of the cores and during transient fault conditions. The influence of FCL topology and alternative low-cost core materials, on the flux characteristics and overall device performance, is also discussed.

High Sensitive Magnetic Nanosensors Based on Superconducting Quantum Interference Device

Nanosized superconducting quantum interference devices (nano-SQUIDs) offer the possibility to investigate small spin populations and the magnetization of nanoparticles opening new horizons in the world of nanomagnetism. We will report recent results about the design, the fabrication and the characterization of high sensitive magnetic nanosensors based on nano-SQUID having a flux capture area of 0.5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In order to achieve a better magnetic flux resolution a proper device design has been developed. The fabrication process is based on the electron beam lithography and a lift-off procedure in a 25 nm thick Nb layer. Measurements of current-voltage and current vs. magnetic flux characteristics have been reported. The comparison between the nanodevice based on the improved design and a standard one has shown the effectiveness of the new design. Preliminary measurements at T=4.2 K on Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanoparticles having a size of 8 nm have been reported, showing the capability of such nanodevices to investigate the magnetism at a submicrometric scale.

Concurrent Design of Interior-Permanent-Magnet Machines for Self-Sensing and Power Conversion

This paper presents the concurrent design of interior permanent magnet (IPM) machines for self-sensing and power conversion. Simulations with finite-element analysis are mainly used to gain insight of magnetic behavior and flux characteristics in the evaluated machines. q-axis flux barriers are used in the concurrent rotor design due to their effective reduction in saturation effect from load current. A saliency characteristic with Ld >; Lq obtained, and benefits in self-sensing and power conversion are found in the concurrent design of IPM machines. Design effects of different rotor structure parts are also evaluated.

Current characteristics of mesoscopic rings in quantum Smoluchowski regime

In normal mesoscopic metals of a ring topology persistent currents can be induced by threading the center of the ring with a magnetic flux. This phenomenon is an example of the famous Aharonov-Bohm effect. In the paper we study the current vs the external constant magnetic flux characteristics of the system driven by both the classical and the quantum thermal fluctuations. The problem is formulated in terms of Langevin equations in classical and quantum Smoluchowski regimes. We analyze the impact of the quantum thermal fluctuations on the current-flux characteristics. We demonstrate that the current response can be changed from paramagnetic to diamagnetic when the quantum nature of the thermal fluctuations increases.