Magnetic Gap Research Articles

Diagnostic Insights for Optimal Avanza/Xenia AC Performance

This study investigates the AC system of Avanza/Xenia vehicles through diagnostic procedures aimed at identifying potential issues and ensuring adherence to maintenance standards. The air conditioning (AC) system in vehicles plays a pivotal role in ensuring driver and passenger comfort, necessitating regular monitoring and maintenance. Utilizing measuring tools such as compressors and multimeters, the main components including the magnetic clutch and evaporator were assessed. Results indicate that measured values, including magnetic clutch coil resistance (3.9 ohms), magnetic clutch gap (0.5 mm), and blower system resistance (ranging from 0 to 2.6 ohms), fall within acceptable service limits outlined in the Avanza/Xenia manual. Consequently, no repair procedures were deemed necessary, affirming the normal condition and suitability for use of the AC system. This research fills a knowledge gap by providing a systematic diagnostic approach for evaluating vehicle AC systems, offering implications for maintenance practices in ensuring optimal performance and longevity. Highlights: Routine maintenance prolongs AC system lifespan. Accurate diagnosis prevents potential issues. Component inspection ensures system health. Keywords: PMCB, Vehicle Air Conditioning System, Maintenance, Repair, Troubleshooting

Five-phase space vector carrier-based PWM for third harmonic injection

Five-phase AC drives allow a third harmonic voltage to be fed into the stator winding – in addition to the fundamental voltage – to generate a third harmonic magnetic air gap field. This allows the generation of an additional small constant torque. Furthermore, the undesirable saturation harmonics that occur with saturated iron can be compensated. The desired third harmonic voltage is commonly generated via time-consuming space vector PWM algorithms, which are not well-suited for real-time application, or via look-up tables, which require an increased storage capacity. In our case, the desired third harmonic voltage is generated in the five-phase voltages by adding a non-sinusoidal zero-sequence voltage with five times the fundamental frequency to the fundamental voltage reference signals in carrier-based pulse width modulation (PWM) with a constant switching frequency. This is equivalent to a space vector PWM method (SVPWM) and avoids a significantly high calculation effort. The PWM algorithm programmed in MATLAB in real time allows the fast generation of a third harmonic voltage per phase with freely definable amplitude and phase shift without requiring a lot of storage capacity.

First-Principles Calculations to Investigate Spin-Oriented Magnetic Phases, Band Gaps, Elastic, and Thermodynamic Calculations of VNi2O4

In this study, spin and U-Coulomb interactions-dependent electronic structure, pressure-dependent elastic, and thermodynamics studies of VNi2O4 were performed. The ferromagnetic (FM) phase was the most stable magnetic phase. The lattice parameter was calculated as 8.32 Å. The bulk modules were calculated as 197.695 GPa and 198.038 GPa, respectively, in the initial condition and the elastic calculations, so the initial and elastic conditions were compatible. VNi2O4 material had band gaps of 1.597 eV, 2.159 eV, 2.659 eV, 3.094 eV, 3.439 eV, 3.729 eV, and 3.978 eV in the majority spin electrons in the Generalized Gradient Approximation (GGA), and U-Coulomb interactions (U = 1, 2, 3, 4, 5 and 6 eV), respectively. Hence, it was a true half-metallic ferromagnetic. VNi2O4 was ductile at 0 GPa, with a Debye temperature of 586.596 K. The net magnetic moment of VNi2O4 was 6.00 µB/f.u. As a result, VNi2O4 provides all the necessary conditions for spintronic applications.

In Search of the Proper Dimensions of the Optimum In-Wheel Permanent Magnet Synchronous Motor Design

In this paper, a new approach to the optimized design of outer rotor Permanent Magnet Synchronous Motors (PMSMs) for in-wheel light electric vehicle (LEV) applications is presented. The optimized design study is based on various dimensions such as back iron depth, permanent magnet depth and air gap length. The novel method is developed to reveal the quality factor of design (QFD), which implies the maximum possible performance results, and determine the best possible design for in-wheel PMSMs for direct-drive LEV applications. Therefore, the thickness of the back iron, permanent magnet and air gap dimensions are altered accordingly to obtain an optimized design. This design study is conducted for an in-wheel PMSM that has rated values of 2.5 kW, 150 V, 900 min−1, and 24-slot/20-pole configuration intended for LEV propulsion. These designs are simulated in order to obtain the maximized combination of efficiency, shaft power, shaft torque and a minimized combination of total weight, iron losses, copper losses, input current and cogging torque. The measure of the optimized parameters is named QFD, which indicates the goodness of the design through the use of radar charts. The values of the essential coefficients of QFD may vary for different applications, e.g., the design of PMSMs used in traction applications has some certain criteria that imply high-performance operation. Additionally, the QFD can guide motor manufacturers as a starting point for a design study.

Performance investigation of conduction-cooled cryogenic permanent magnet undulator at high beam currents

A conduction-cooled cryogenic permanent magnet undulator, CU15, with a period length of 15 mm and 133 periods has been successfully developed. This undulator has been operated at the Taiwan Photon Source (TPS) storage ring at a beam current of 500 mA for more than 3 years. In CU15, two cryocoolers are used to cool the PrFeB magnets to 80 K. The effective magnetic field measures 1.33 Tesla for a magnet gap of 4.2 mm, maintaining an rms phase error below 2.6°. The bunch length of the electron beam in TPS is as short as 16 psec, leading to a serious issue with high beam-induced heating in CU15. This report addresses the above issues and provides detailed adaptations of CU15 to operate at a beam current of 500 mA. Published by the American Physical Society 2024

Thermodynamics of resonating-valence-bond states toward the understanding of quantum spin liquid phenomena.

A quantum spin liquid (QSL) is a state of matter in which spins do not exhibit magnetic order. In contrast to paramagnets, the spins in a QSL interact strongly, similar to conventional ordered magnets; however the thermodynamic stability of QSLs is rarely studied. Here, the thermodynamic properties of centered hexagon nanoclusters were investigated using the Hubbard model, which was solved using exact numerical diagonalization. The total spin, spin-spin correlation functions, local magnetic moments, charge and spin gaps, and magnetocaloric effect were analyzed for a half-filled band as a function of the ratio between the on-site Coulomb repulsion and electronic hopping (U/t). The centered hexagon nanocluster exhibited an antiferromagnetic (AFM) behavior with exotic magnetic ordering. Resonating-valence-bond (RVB) states were observed for intermediate values of U/t, in which short-range spin-spin correlation functions were suppressed to minimize spin frustration. The AFM order was examined in terms of the Néel-like temperature derived from the temperature dependence of the magnetic susceptibility. An interesting result is that the systems under external magnetic fields exhibited an inverse magnetocaloric effect, which was remarkable for intermediate values of U/t, where the RVB state was observed. Owing to the novel discovery of exotic magnetic ordering in triangular moiré patterns in twisted bilayer graphene (TBLG) systems, these results provide insights into the onset of magnetism and the possible spin liquid states in these graphene moiré materials.

Prediction of superhard C1+xN1-x compounds with metal-free magnetism and narrow band gaps.

The scarcity of superhard materials with magnetism or a narrow band gap, despite their potential applications in various fields, makes it desirable to design such materials. Here, a series of C1+xN1-x compounds are theoretically designed by replacing different numbers of nitrogen atoms with carbon atoms in the synthesized C1N1 compound. The results indicate that the compounds C5N3 and C7N1 possess both superhardness and antiferromagnetic ordering due to the introduction of low-coordinated carbon atoms. The hardness of the two compounds is about 40.3 and 54.5 GPa, respectively. The magnetism in both compounds is attributed to the unpaired electrons in low-coordinated carbon atoms, and the magnetic moments are 0.42 and 0.39 μB, respectively. Interestingly, the magnetism in C5N3 remains unaffected by the external pressure used in this study, whereas C7N1 becomes nonmagnetic when the pressure exceeds ∼80 GPa. Electronic calculations reveal that both compounds behave as indirect band gap semiconductors, with narrow energy gaps of about 0.30 and 0.20 eV, respectively. Additionally, the other two compounds, C6N2-I and C6N2-III, exhibit nonmagnetic ordering and possess hardness values of 52.6 and 35.0 GPa, respectively. C6N2-I behaves as a semiconductor with an energy gap of 0.79 eV, and C6N2-III shows metallic behavior. Notably, the energy gaps of C5N3 and C6N2-I remain nearly constant under arbitrary pressure due to their porous and superhard structure. These compounds fill the gap in magnetic or narrow band gap superhard materials, and they can be used in the spintronic or optoelectronic fields where conventional superhard materials are not suitable.

Nanocrystalline alternative rare earth-iron-boron permanent magnets without Nd, Pr, Tb and Dy: A review

The continuous increase in the output of Nd-Fe-B permanent magnets leads to the increasing consumption of rare earth (RE) metals of Nd, Pr, Tb and Dy. As a result, a serious unbalanced utilization of RE resource occurs. To reduce the use of these critical REs, high abundance REs of Y, La, Ce and even Gd and Ho have been proposed to partly substitute Pr and Nd in sintered magnets and rapid-quenched nanocrystalline magnetic powders. Recently, the cost-effective RE-Fe-B magnets without Nd, Pr, Tb and Dy have also been developed. This type of magnet is preliminarily designed to bridge the magnetic properties gap between hard ferrites and bonded Nd-Fe-B magnets, which shows the potential applications in voice coil motor, spindle motors and magnetic resonance imaging systems. This review summarizes the progress of RE-Fe-B-type magnets containing no Nd, Pr, Dy and Tb based on the world-wide investigations and our recent findings. The fundamentals of intrinsic magnetic properties of Y, La, Ce based RE2Fe14B phases are introduced first. The relationship between magnetic properties and microstructure of rapidly quenched and bulk RE-Fe-B magnets with nanocrystalline structure is then emphatically discussed. Hard magnetic properties and performance/cost ratio of various RE-Fe-B alloy systems are summarized and compared. Furthermore, the current discoveries and the existing challenges are discussed. Some potential strategies for the future research in this field are finally proposed.

Multiferroic Properties of Co, Ru, and La Ion Doped KBiFe2O5.

The magnetic, electric, dielectric, and optical (band gap) properties of ion doped multiferroic KBiFe2O5 (KBFO) have been systematically investigated utilizing a microscopic model and the Green's function theory. Doping with Co at the Fe site and Ru at the Bi site induces changes in magnetization, coercive field, and band gap energy. Specifically, an increase in magnetization is observed, while the coercive field and band gap energy decrease. This behavior is attributed to the distinct ionic radii of the doped and host ions, leading to alterations in the exchange interaction constants. The temperature dependence of the polarization P reveals a distinctive kink at the Neel temperature TN, which shifts to higher temperatures with an increase in the applied magnetic field h. Furthermore, doping with Ru and La leads to an increase in polarization. The temperature dependence of the dielectric constant exhibits two peaks at the Neel temperature TN and the Curie temperature TC. Notably, these peaks diminish with increasing frequency. Additionally, the dielectric constant demonstrates a decrease with the rise in the applied magnetic field h. This study sheds light on the intricate interplay between ion doping, structural modifications, and multifunctional properties in KBFO, offering valuable insights into the underlying mechanisms governing its behavior across various physical domains.

High-precision positioning of Hall probes for SCU magnetic field measurement

A planar superconducting undulator (SCU) prototype with the magnetic length of 4 m and the magnetic gap of 5 mm is being developed for Shanghai High Repetition rate XFEL and Extreme Light facility (SHINE) to generate vertical linear polarization FELs. The magnetic field measurement device based on Hall probes has been built for the SCU. Three Hall probes mounted on a sledge are used to measure the magnetic field in the undulator gap. The three-dimensional positioning system based on the Gaussian laser beam for the sledge and the Hall probes is presented in detail in this paper.

Magnetic Modulation of the Piezoelectric Polyvinylidene Fluoride Film Energy Harvester for Noncontact Dynamic Characteristics Control

This paper aims to improve the performance of the piezoelectric buckled beam under low vibration environment using the noncontact magnetic modulation method. Based on the bi-stable buckling beam structure, the magnetic force is introduced to capture more energy. In order to investigate the influence of magnetic force in the process of vibration, the dynamic response of the harvester is analyzed under different magnetic force through numerical simulation and experiment. It is found that the magnetic force has a softening effect on the structure, namely, it could reduce the stiffness of the buckled beam. Therefore, the energy harvester could realize large-amplitude vibration under low-amplitude or low-frequency vibration with the help of magnetic force. The experimental results show that the harvester can realize inter-well vibration only when the vibration acceleration is 3.5[Formula: see text]g and the frequency is 15[Formula: see text]Hz without the magnetic force. The harvester only needs 2.5[Formula: see text]g acceleration or 10[Formula: see text]Hz vibration frequency to realize the large-amplitude vibration. While in the case of 12[Formula: see text]mm magnetic gap. After the magnetic force is introduced in the harvester, the voltage output under 2.5[Formula: see text]g acceleration is increased from 1 to 4[Formula: see text]V, and the voltage output at 10[Formula: see text]Hz vibration frequency is increased from 0.2 to 2[Formula: see text]V. Therefore, the proposed magnetically tuned bi-stable energy harvester can better operate in low frequency and low amplitude environments.

Magnetic, pressure-dependent elastic, and band gap calculations of VCo2O4 oxide spinel via GGA, GGA+mBJ, and GGA+U

The basis of spintronics is the technology involving nano-sized devices whose spins are directed. Therefore, materials that provide magnetic and 100 % spin polarization are remarkable. The ferromagnetic phase of VCo2O4 has obtained the most stable. In the GGA approximation, the equilibrium lattice constant and magnetic moment values were 8.34 Å and 10.00 μB/f.u., respectively. The band gaps in the GGA and GGA + mBJ approximations were calculated as 1.262 eV and 4.847 eV. The band gap values for Coulomb interactions U = 1, 2, 3, and 4 eV were obtained as 1.268 eV, 1.273 eV, 1.279 eV, and 1.286 eV, respectively. The elastic calculations showed that VCo2O4 was mechanically stable and ductile. The Debye temperature was calculated as 565 K at 0 GPa pressure. As a result, VCo2O4 oxide spinel has been obtained as a true half-metallic ferromagnetic material and will be a very good alternative for spintronic applications.

Crossover from gapped-to-gapless Dirac surface states in magnetic topological insulator MnBi2Te4

Intrinsic magnetic topological insulators (MTIs) host exotic topological phases such as quantized anomalous Hall insulating phase, arising due to the large magnetic exchange gap. However, the interplay of magnetism and topology in these systems in different temperature regimes remains elusive. In this work, we present the logarithmic temperature-dependence of conductivity for sub-100 nm thick exfoliated flakes of MTI MnBi2Te4 in the presence of out-of-plane magnetic fields and extracted the linear slope, κ. We observed a characteristic change, in the low-temperature regime, indicating the gapped Dirac surface state according to Lu–Shen theory. We also report the recovery of topological properties in the system via the weak-antilocalization effect in the vicinity of antiferromagnetic to paramagnetic transition and in the paramagnetic regime. Hikami–Larkin–Nagaoka analysis suggested the presence of topological surface states. Therefore, our study helps in understanding how intrinsic magnetism masks topological properties in an MTI as long as magnetic ordering persists.

Using inerter-integrated absorbers to improve the performance of an in-wheel motor system

The in-wheel motor (IWM) is a promising advancement in electric vehicle propulsion since it offers greater packaging efficiency and torque vectoring capabilities than a chassis-mounted motor. However, the increased unsprung mass degrades the vehicle dynamics by increasing body vertical acceleration (BVA) and tyre dynamic load (TDL), worsening ride comfort and road-holding respectively. Another important consideration is magnetic gap deformation (MGD), which results from the deflection between the motor stator and rotor. Reducing MGD improves the motor reliability and longevity. This paper addresses these issues by incorporating inerters into an existing IWM model. They are incorporated into the strut and bushes to control BVA, TDL and MGD. The system optimised for MGD resulted in a deflection reduction of over 98% without compromising performance of the other indices. Optimising the strut and bushes for BVA and TDL reduced them by 20% and 9% respectively without degrading MGD. A sensitivity analysis of the results is presented. Here the damping and inertance values are varied by 20% from the optimum, and the resulting performance still improves upon the default. It is concluded that there are significant potential improvements where inerters are included in an in-wheel motor system.

Shot noise in topological insulator-based ferromagnet/p-wave superconductor junctions

The differential shot noise and Fano factor in topological insulator-based ferromagnet/p-wave superconductor (TI-based FM/p-wave SC) junctions is theoretically investigated based on the Dirac-Bogoliubov-de Gennes equation. Three kinds of pairings px, py, and px+ipy-waves for SC are chosen. It is found that the shot noise spectrum strongly depends on the finite-quasi-particle lifetime, the magnetic gap m induced by an applied magnetization, the Fermi-energy mismatch between FM and SC as well as the type of the pair potential symmetry. Shortening the quasi-particles lifetime leads to the dips in the shot noise smoothed out. Increasing the magnetic gap can suppress the shot noise and Fano factor when the conventional Andreev retro-reflection is the dominant process but the shot noise can be enhanced when the dominant process is the specular Andreev reflection. Which type of reflection dominates the tunneling process with a turning point at the Fermi energy EF =m, where the values of shot noise in all energy ranges become zero. This result can be used not only to distinguish the specular Andreev reflection from the Andreev retro-reflection in thin film TI-based FM/p-wave SC structures but also to determine the energy-mass gap induced by the applied magnetization.

Study of Andreev reflection in topological insulator-based ferromagnet/ [formula omitted] wave superconductor structures

The Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory are used to calculate the tunneling conductance and shot noise in topological insulator-based ferromagnet/ dx2−y2+idxy mixed wave superconductor (TI-based FM/ dx2−y2+idxy SC) junctions. The Andreev reflection is investigated by analyzing the conductance and shot noise. Results show that the Andreev reflection process strongly depend on the magnetic gap m in FM, the gate potential U applied to the electrode on top of SC, and the magnitude of the ratio of Δ1/Δ0 with Δ0(Δ1) the absolute of pair potential of dx2−y2(dxy) component. The specular Andreev reflection can be enhanced by m as well as U. The conventional Andreev retro-reflection, however, can be enhanced by U but be suppressed by m. Which of the two reflections dominates the tunneling phenomenon exists a turning point at m = EF where both the tunneling conductance and differential shot noise become zero. This can be used as a criterion for distinguishing between the specular Andreev reflection and the Andreev retro-reflection in thin film TI-based FM/ dx2−y2+idxy SC structures. In addition, the dx2−y2+idxy pairing symmetry as well as the magnitude of magnetic gap can be determined by the experiment of scanning tunnel spectroscopy.

A magnetic head-based eddy current displacement sensing method

Eddy current displacement sensors are popular for sensing changes in displacement in industrial fields with many advantages. The eddy current induced by a conventional coil is distributed over a large range and the energy is not concentrated. The size of the minimum measured surface is 1.5 to 3 times the diameter of the coil. A magnetic head-based eddy current displacement sensor is proposed in this paper. Theoretical analysis confirms that the coil generates a highly concentrated magnetic field at the magnetic core gap. The simulations based on the finite element method are performed. The simulation results demonstrate that the proposed method can induce the eddy current field which has a small distribution range and high degree of concentration of energy on the surface of the specimen. Finally, experiments are conducted for different sized ring-shaped surfaces. The high similarity between the experimental results indicates that the magnetic head-based eddy current displacement sensor can induce a highly focused eddy current field with a distribution range of 3 mm. The sensitivity of the sensor is 5 V mm−1 and the spatial resolution of the sensor is 3 mm.

Design and development of vacuum chamber for superconducting undulator at IHEP

Superconducting undulators (SCUs) are crucial components for advanced photon sources and have broad applications. IHEP is currently developing SCU, which requires a vacuum chamber to provide a beam path and protect the superconducting magnets from image currents induced by the beams. However, due to the narrow magnetic gap and low temperature of the SCU, designing and processing its vacuum chamber presents challenges in terms of mechanical design, positioning, and intercepting synchrotron radiation that could damage the sensitive superconducting magnets. The SCU vacuum chamber is divided into three parts based on location and function: chamber inside the cryostat as well as upstream and downstream chambers outside it. The complex fit of the constant aperture vacuum chamber inside the cryostat with both magnets and cryostat ensures high-current operation while also safely managing dynamic heat loads imposed by beams. Using an SCU operating on HEPS as an example shows how smooth transitions between upstream/downstream and storage ring chambers effectively absorb synchrotron radiation to protect magnets and downstream equipment from damage caused by synchrotron radiation exposure. Simulations are performed to check the possible effects of synchrotron radiation on the mechanical properties, the ultimate vacuum of these chambers and to calculate the beam impedance. Finally, two solutions for using the vacuum chamber as a channel for measuring the magnetic field of the SCU in the operating state are discussed.

Biofilm prevention in the generator of a direct drive wave energy converter

Power take off in a wave energy converter has a number of unique requirements. It must convert low speed oscillating motion into electricity in a reliable, low maintenance manner. A direct drive system, where the electrical machine is optimised to operate at low speed, has the potential to offer a mechanically robust and simple solution. Similar to a hydraulic power take off, the only regular maintenance would be to inspect and replace the seal between moving parts. One strategy for removing regular maintenance is to have an unsealed system, i.e. one where sea water is allowed throughout the electrical machine. A fully flooded electrical machine has benefits in terms of cooling, but poses challenges relating to reliability, corrosion, biofouling and lubrication.
 Biofilm refers to a thin layer of fouling organisms which can interfere with the operation of components. Recent work has found that submerged surfaces can be kept free of biofouling using projected ultraviolet (UV) light from LEDs. This paper discusses the testing procedure and impact of the UVC irradiation on biofilm prevention within the active part of an electric generator in a systematic manner, with a view to accelerate its translation to full-scale applications.
 A prototype generator is being developed which will be installed in the North Sea, consisting of a submerged linear tubular electrical machine. A magnetic tubular translator will oscillate within a cylinder that houses stator coils. Lubrication will be by way of solid polymer bearings. In order that the active part of the electrical machine can oscillate smoothly, it is imperative that biofilm is prevented from colonising on the bearing surface, which also makes up the magnetic gap of the electrical machine.
 The system will have a slow reciprocating oscillation, with a peak speed of perhaps 2m/s. For most wave energy converters there will be brief static periods twice in every wave, and in calm seas these could be prolonged to several hours or even days. In low energy sea states oscillation amplitude could be less than the fully rated amplitude, meaning different parts of the bearing surface could be exposed for different amounts of time.
 Early-stage work is underway to investigate the use of UV irradiation in the active part of the electrical machine and bearing surface as biofilm prevention. Flat panels (600mm x 220mm) are used to simulate the original surfaces between moving parts. To achieve biofilm growth, an artificial slime farm was deployed which allows test panels to be subjected to a continuous dynamic flow. The light source of UV irradiation was provided by Light Emitting Diodes (LEDs) with 278nm wavelength. The effectiveness of the biofilm prevention by UVC were evaluated by Image Analysis
 The results indicate that UVC can significantly control biofilm presence on the panels. It also has demonstrated that intermittent UV can achieve successful biofilm prevention on submerged surfaces. However, observations indicate the actual UVC light intensity may perform below the manufacturer’s specifications, and this could lead to a detrimental effect on its biofilm control performance.

An Innovative H-Type Flux Switching Permanent Magnet Linear Generator for Thrust Force Enhancement

In this paper, two H-type flux switching permanent magnet linear generators with outer-translator and inner-translator configurations are discussed and compared to a more conventional flux switching topology. The stators consist of H-Type modules housing circumferential coils and are surrounded by two annular permanent magnets. In conventional flux switching machines, the windings are orientated perpendicular to the direction of motion and the conductors twist around the magnets. In H-type topologies, the orientation of the windings is in the same plain as the magnets and parallel to the direction of motion, resulting in an increase in flux linkage. The proposed topologies are designed for a low operating speed and a large magnetic gap, as found in wave energy converters. All topologies are optimized using the Taguchi optimization approach with the goals of reducing force ripple and increasing the average thrust force and efficiency. The 2D finite element method (FEM) is used in the optimization stage to calculate the optimized parameters of the presented generators, after which the optimized structures are simulated using 3D FEM, and the results are extracted. The results of the optimization show that the H-type topologies deliver a 20% higher shear stress whilst offering an easier to assemble structure.