Neodymium Iron Boron Permanent Magnets Research Articles

Hybrid-Magnet Variable Flux Memory Machine With Improved Field Regulation Capability for Electric Vehicle Applications

This article aims to investigate a novel hybrid-magnet variable flux memory machine (VFMM) with improved field regulation capability for electric vehicle applications. Two sets of permanent magnets (PMs), i.e., high-energy-density neodymium–iron–boron PM and low coercive force (LCF) PM, are arranged in a delta array to improve field regulation capability and torque density. The machine topology, key features, and operating principle of the presented machine are demonstrated. Based on the simplified magnetic circuit model, the underlying design tradeoffs of the presented machine are revealed qualitatively. The nonlinear magnetic circuit model of the presented machine taking saturation and hybrid-magnet leakage flux into consideration is built for machine analysis. Electromagnetic performance comparisons are carried out by finite element analysis between the presented VFMM and the existing VFMM. The results show that the presented machine can achieve significantly improved flux regulation capability while maintaining the high output torque due to the improved arrangement of hybrid magnetic branches and enhanced flux concentration effect. Finally, the investigated VFMM is prototyped. The operating principle and predicted results are verified by experimental results.

NO2 Sensor Based on Faraday Rotation Spectroscopy Using Ring Array Permanent Magnets.

Faraday rotation spectroscopy (FRS) exploits the magneto-optical effect to achieve highly selective and sensitive detection of paramagnetic molecules. Usually, a solenoid coil is used to provide a longitudinal magnetic field to produce the magneto-optical effect. However, such a method has the disadvantages of excessive power consumption and susceptibility to electromagnetic interference. In the present work, a novel FRS approach based on a combination of a neodymium iron boron permanent magnet ring array and a Herriott multipass absorption cell is proposed. A longitudinal magnetic field was generated by using 14 identical neodymium iron boron permanent magnet rings combined in a non-equidistant form according to their magnetic field's spatial distribution characteristics. The average magnetic field strength within a length of 380 mm was 346 gauss. A quantum cascade laser was used to target the optimum 441 ← 440 Q-branch nitrogen dioxide transition at 1613.25 cm-1 (6.2 μm) with an optical power of 40 mW. Coupling to a Herriott multipass absorption cell, a minimum detection limit of 0.4 ppb was achieved with an integration time of 70 s. The low-power FRS nitrogen dioxide sensor proposed in this work is expected to be developed into a robust field-deployable environment monitoring system.

The Novel Low Reluctance Superconducting Permanent Magnet Linear Generator for Oceanic Wave Energy Extraction

In this paper, the low reluctance superconducting direct drive linear generator (DDLG) for harvesting oceanic wave is presented. At first, a permanent magnet DDLG is designed in the ANSYS/Maxwell environment. The DDLG with both the copper and superconducting winding are characterized with finite element analysis. The DDLG is analyzed with the conventional and recently developed M5 Carlite magnetic cores. High graded neodymium iron boron permanent magnet, N46SH is selected for the DDLG to create strong magnetic field. It is analyzed that the proposed superconducting DDLG with M5 Carlite magnetic core and N46SH permanent magnet produces 294 kW more electrical power compared to that of the DDLG with copper conductor. It is also found that the stator size of the proposed DDLG is much smaller than the conventional one for designing the winding with superconducting tape.

Substitution Effect of Magnetic Materials in Halbach Cylinder for Magnetic Refrigerators

In this paper, we present the magnetic refrigeration by magnetocaloric effect, for which the magnetic flux distribution has been modified in the Halbach cylinder. The insertion of a soft magnetic rod in the bore led to the alternating magnetic field with two regions of high flux density for magnetization and two regions of low flux density for demagnetization of magnetocaloric materials in the annular gap. The two-dimensional numerical simulations by the finite element method using COMSOL Multiphysics and Poisson SUPERFISH demonstrated the substitution effect of neodymium–iron–boron permanent magnets by soft magnetic low-carbon steels. The optimized soft magnetic cross-sectional area of 0.04 m2 in the Halbach cylinder gave the maximum flux density of 2 T in the air gap, comparable to the peak field of existing prototypes. The flux density is further increased and became the largest when the ratio of external to internal radius of the cylinder is at the maximum. The cooling performance is also affected by the size of the cylinder, and the substantial value is obtained in a practical design with reserved air gap for magnetocaloric materials.

Design of the Permanent Magnet Diverter for Deflecting Electrons on Wide-field X-ray Telescope

The Einstein Probe (EP) Satellite is a mission of Chinese Academy of Sciences, which is planned to be launched at the end of 2022. Its main work is to explore all-sky transient X-ray sources and constantly various X-ray sources. It will carry a Wide-field X-ray Telescope (WXT) and two Follow-up X-ray Telescopes (FXT). It is dedicated to investigate time-domain astronomy and to monitor the sky in the soft X-ray band. For the WXT, the electrons with kinetic energy below 1 MeV will pollute the background when they pass through the optic system. So, it is a key issue to remove the electrons with low energy out of the beam. A Permanent Magnet Diverter (PMD) is designed and fabricated for the WXT. Its main purpose is to separate the background electrons from the X-ray detecting system by re-directing the electrons. In order to minimize the magnetic flux leakage and the magnetic moment, a design of circular magnetic field is proposed by arranging the neodymium iron boron permanent magnet blocks appropriately, which can reduce the length of electron deflecting paths when they pass through the magnetic field region. The total weight is taken into considerations to optimize the structure of the PMD during design. Furthermore, the motion of electrons in the PMD and their entering paths towards the detector are simulated to improve the structure of the PMD. At the end, the eigenfrequency and mode shapes are analyzed to make sure the PMD could work normally on the satellite platform. The design and analysis of the PMD are presented detailed in the paper.

Experimental studies on the influence of axial and radial fields of sintered neo-delta magnets in reforming the energy utilization combustion and emission properties of a hydrocarbon fuel

ABSTRACT Permanent magnets based on rare earth components have been increasingly finding their applications in modern technologies. Although the magnetic properties tend to deteriorate rapidly at temperatures in excess of 150ºC, sintered NdFeB magnets can be employed in reforming the physical and combustion properties of hydrocarbon fuels. In the present investigation, two different magnetization patterns of high-grade NdFeB magnets are applied in varying intensities on a multicylinder MPFI engine fueled by gasoline and the alteration in combustion and emission properties of the fuel are studied. The magnetic field restructures the hydrocarbon molecules and causes the pseudo clusters to break away thus reducing the inherent viscosity and enhancing the association of hydrocarbon molecules with the oxidizer. The effectiveness of two different magnetization patterns of sintered NdFeB magnetic material in reforming the combustion characteristics is studied and compared. The study shows a maximum increase of 9.2% in power output and 7.74% in thermal efficiency of the test engine along with a significant reduction in the generation of toxic emissions that are the byproducts of combustion. The study also concludes that radial magnetic fields are more effective in conditioning the fuel and reducing the emission of CO, HC, and NOx by 8.57%, 5.52%, and 1.25% compared to the same intensity fields under axial magnetization. The combustion behavior of gasoline is studied under both field patterns. The statistical analysis of mean effective pressures through radar plots is conclusive of the reduction in cycle by cycle variations under magnetic field-assisted combustion. Abbreviations: NdFeB:Neodymium Iron Boron permanent magnet; SmCo:Samarium Cobalt permanent magnet; MPFI:Multipoint Port Fuel injection; BP:Brake Power; BTE:Brake Thermal Efficiency; BSFC:Brake Specific Fuel Consumption; NHRR:Net Heat Release Rate; IMEP:Indicated Mean Effective Pressure; COV:Coefficient of Variation; CO:Carbon Monoxide; CO2:Carbon dioxide; HC: hydrocarbon; NOxOxides of Nitrogen.

Performance Testing and Analysis of Synchronous Reluctance Motor Utilizing Dual-Phase Magnetic Material

While interior permanent magnet (IPM) machines have been considered state of the art for traction motors, synchronous reluctance (SynRel) motors with advanced materials can provide a competitive alternative. IPM machines typically utilize neodymium iron boron permanent magnets, which pose an issue in terms of price, sustainability, demagnetization at higher operating temperatures, and uncontrolled generation. On the other hand, SynRel machines do not contain any magnets and are free from these issues. However, the absence of magnets as well as the presence of bridges and centerposts limit the flux-weakening capability of a SynRel machine, and limit the achievable constant power speed ratio without having to significantly oversize the machine and/or the power converter. In this paper, a new material referred to as the dual-phase magnetic material, where nonmagnetic regions can be selectively introduced within each lamination, will be evaluated for SynRel designs. The dual-phase feature of this material enables nonmagnetic bridges and posts, eliminating one of the key limitations of the SynRel designs in terms of torque density and flux weakening. This paper will present the design, analysis, and test results of an advanced proof-of-concept SynRel design utilizing dual-phase material with traction applications as the ultimate target application.

Evaluation of Vibrational PiezoMEMS Harvester That Scavenges Energy From a Magnetic Field Surrounding an AC Current-Carrying Wire

This paper reports on a low-frequency vibrational piezoelectric energy harvester that scavenges energy from a wire carrying an ac current. The harvester is described, fabricated, and characterized. The device consists of a silicon cantilever with an integrated piezoelectric capacitor and a proof-mass that incorporates a permanent magnet. When brought close to an ac current carrying wire, the magnet couples to the ac magnetic field from a wire, causing the cantilever to vibrate and generate power. The device was fabricated from a silicon-on-insulator substrate using microelectromechanical systems (MEMS) technology. The charge generating capacitor uses a CMOS compatible aluminum nitride piezoelectric material and fabrication process. The device uses a commercial neodymium iron boron permanent magnet that is post-fabrication assembled with the device. The measured average power dissipated across an optimal load of 2 $\text{M}\Omega $ was $1.5~\mu \text{W}$ . This was obtained by exciting the device into mechanical resonance with a peak displacement of 3 mm using the electro-magnetic field from a 2-A source current. The measurements also reveal that the device’s electrical response is nonlinear due to mechanical nonlinearity of the device. In addition, bandwidth broadening by 250% is demonstrated by means of vibro-impact approach. [2016-0263]

Design of Synchronous Reluctance Motor Utilizing Dual-Phase Material for Traction Applications

While interior permanent magnet (IPM) machines have been considered the state-of-the art for traction motors, synchronous reluctance (SynRel) motors with advanced materials can provide a competitive alternative. IPM machines typically utilize neodymium iron boron permanent magnets, which pose an issue in terms of price, sustainability, demagnetization at higher operating temperatures, and uncontrolled generation. On the other hand, SynRel machines do not contain any magnets and are free from these issues. However, the absence of magnets as well the presence of bridges and center post limit the flux-weakening capability of a SynRel machine and limit the achievable constant power speed ratio for a given power converter rating. In this paper, a new material referred to as the dual-phase magnetic material will be evaluated for SynRel designs. This material allows for nonmagnetic regions to be selectively introduced in the bridge and post regions, thereby eliminating one of the key limitations of the SynRel designs in terms of torque density and flux weakening. This paper will focus on advanced SynRel designs utilizing dual-phase material targeting traction applications. The paper will provide a detailed comparison between a dual-phase SynRel design, a conventional SynRel design, and a spoke PM design with rare-earth-free magnets. It will highlight the key tradeoffs in terms of power density, efficiency, and flux-weakening capability.

A Novel Linear-Rotary Permanent-Magnet Actuator Using Interlaced Poles

This paper proposes a novel linear–rotary permanent-magnet actuator (LRPMA) with interlaced poles, which has the merit of using only 50% of the neodymium–iron–boron permanent magnets when compared with those used in traditional Halbach structure. By assuming the stator is slotless, the magnetic field distribution of the LRPMA is initially analyzed using the magnetic scalar potential in the Cartesian coordinate system. A method for calculating the relative permeance by Schwarz–Christoffel transformation (SCT) is subsequently deduced to analyze the magnetic field in detail and predict the cogging force/torque of LRPMA very accurately. The analytical linear cogging force and rotary cogging torque are derived and verified for the design optimization of the actuator. The 3-D finite-element method is used to verify the correctness and effectiveness of the proposed SCT.

Design of NdFeB Permanent Magnet DC Generator

The advantages and development trend of automotive neodymium iron boron permanent magnet DC generator is summarized, analyzed the operation mode of neodymium iron Peng Yongci DC generator, and puts forward the neodymium iron boron permanent magnet DC generator has broad prospects for development. The design of the key parts of power system -- the neodymium iron boron permanent magnet DC generator, the excitation rotor and the armature winding parameters were designed to meet the needs of neodymium iron boron permanent magnet DC generator and improve the efficiency of the generator.

Guided self-assembly of magnetic beads for biomedical applications

Micromagnetic beads are widely used in biomedical applications for cell separation, drug delivery, and hyperthermia cancer treatment. Here we propose to use self-organized magnetic bead structures which accumulate on fixed magnetic seeding points to isolate circulating tumor cells. The analysis of circulating tumor cells is an emerging tool for cancer biology research and clinical cancer management including the detection, diagnosis and monitoring of cancer. Microfluidic chips for isolating circulating tumor cells use either affinity, size or density capturing methods. We combine multiphysics simulation techniques to understand the microscopic behavior of magnetic beads interacting with soft magnetic accumulation points used in lab-on-chip technologies. Our proposed chip technology offers the possibility to combine affinity and size capturing with special antibody-coated bead arrangements using a magnetic gradient field created by Neodymium Iron Boron permanent magnets. The multiscale simulation environment combines magnetic field computation, fluid dynamics and discrete particle dynamics.

Development and fabrication of an LTCC multilayer coil inducer in a vibration-based electromagnetic meso-generator

This paper presents a new development in the fabrication of vibration-based electromagnetic meso-generators, using a low temperature co-fired ceramic (LTCC) technique. The LTCC process produces multilayer structures consisting of an embedded silver micro-coil in a helical ceramic micro-spring, fabricating an inducer in only a few steps. The design of our device consists of an LTCC inducer, a neodymium–iron–boron permanent magnet and two plastic spacers. The micro-coil and the micro-spring are patterned using a screen-printing technique and a carbon-dioxide laser drilling method, respectively. The silver material and multilayer structure are chosen in order to enhance both current output and power output. A 6-layer coil structure is fabricated, with a cross-sectional area of 900μm2 for each layer. After assembly, the volume of the generator is approximately 718mm3. When operated at 69Hz vibration frequency and vibration amplitude of 0.03mm, the generator yields a maximum voltage output of 44.5mV, a maximum current output of 83.1mA and a power output level of 1.56mW. Results demonstrate that the LTCC meso-generator is a suitable choice to use for the enhancement of electricity.

A magnetically driven PDMS micropump with ball check-valves

In this paper, we present a low-cost, PDMS-membrane micropump with two one-way ball check-valves for lab-on-a-chip and microfluidic applications. The micropump consists of two functional PDMS layers, one holding the ball check-valves and an actuating chamber, and the other covering the chamber and holding a miniature permanent magnet on top for actuation. An additional PDMS layer is used to cover the top magnet, and thereby encapsulate the entire device. A simple approach was used to assemble a high-performance ball check-valve using a micropipette and heat shrink tubing. The micropump can be driven by an external magnetic force provided by another permanent magnet or an integrated coil. In the first driving scheme, a small dc motor (6 mm in diameter and 15 mm in length) with a neodymium–iron–boron permanent magnet embedded in its shaft was used to actuate the membrane-mounted magnet. This driving method yielded a large pumping rate with very low power consumption. A maximum pumping rate of 774 µL min−1 for deionized water was achieved at the input power of 13 mW, the highest pumping rate reported in the literature for micropumps at such power consumptions. Alternatively, we actuated the micropump with a 10-turn planar coil fabricated on a PC board. This method resulted in a higher pumping rate of 1 mL min−1 for deionized water. Although more integratable and compact, the planar microcoil driving technique has a much higher power consumption.

Magnetic equivalent circuit of pm hysteresis synchronous motor

This paper presents the magnetic equivalent circuit of a permanent magnet hysteresis synchronous motor (PMHS). The hybrid synchronous motor consists of 36% cobalt steel hysteresis alloys with neodymium iron boron permanent magnets to improve the overall performances of such a motor. Based on the magnetic equivalent circuit, the control strategy of the PMHS motor is developed. Experimental results confirm the validity of the proposed magnetic equivalent circuit model and show that the hybrid motor exhibits improved speed stability over a wide range.

The asymmetric hybrid wiggler at Orsay

A special multipole hybrid wiggler optimized to produce an intense flux of circularly polarized photons was designed and successfully tested at Orsay. The wiggler was installed on the Synchrotron Radiation Source Super-ACO (E=0.8 GeV) in March 1990. A high flux is produced in a broad energy range extending from the infrared domain to the X-ray region (4 keV). The asymmetric magnetic induction is obtained by inserting drift spaces between the periods. The structure consists of 12 magnetic periods ( lambda =263 mm) made of neodymium iron boron permanent magnet blocks and of 2 families of iron poles (main pole and lateral poles). In each drift space small shimming SmCo/sub 5/ permanent magnets are introduced to cancel the residual field integral. The peak field achieved in a 34 mm gap is 1.05 T. The design, the construction, the magnetic measurements, and some characteristics of the light source are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Neodymium—iron—boron permanent magnets prepared by rapid solidification

The preparation of Nd-Fe-B permanent magnets by rapid solidification processing is described. The initial rapid quench is typically carried out by melt spinning; magnetic hardening can be achieved either by quenching directly from the melt or by annealing an overquenched precursor. In both instances, optimum permanent magnet properties are associated with the formation of a uniform, finely crystalline (<100 nm diam) microstructure consisting primarily of the Nd2Fe14B phase. Consolidation of the rapidly solidified material into isotropic magnets can be achieved by conventional cold compaction of the powder with a resin binder or by hot pressing to full density. Owing to the extremely fine grain size, orientation of the isotropic ribbons by grinding followed by magnetization would be extremely difficult. Crystallographic anisotropy can be achieved, however, by hot deformation. Alignment occurs entirely by thermomechanical means with rotation of the easy crystallographic direction normal to the direction of plastic flow. Energy products to 40 MGOe have been achieved by this technique. Properties of the various types of magnets prepared from this rapidly solidified material are presented as is microstructural data for the material at key points in the manufacturing process.