Position Of Permanent Magnet Research Articles

薄鋼板のハイブリッド磁気浮上システムに関する研究

Recently, demand in improving of quality for thin steel plates used in various industrial products is increasing. Thin steel plates widely used in various industrial products are generally conveyed while in contact with rollers in the conveyance process. To solve this problem, we have proposed a hybrid levitation control system for thin steel plate using the magnetic force generated by permanent magnets, which have no operational costs. In the previous studies, fundamental research on the optimal conditions in terms of the number and position of permanent magnets, was carried out, in which the attractive force of the permanent magnet applied to the rectangular thin steel plate was simplified and modeled. In this study, the gap, number and optimal position of permanent magnets for suppressing the displacement of a magnetically levitated thin steel plate were investigated using thin steel plates (thickness: 0.30 and 0.19 mm).

Air-Barrier Width Prediction of Interior Permanent Magnet Motor for Electric Vehicle Considering Fatigue Failure by Centrifugal Force

Recently, the interior permanent magnet (IPM) motors for electric vehicle (EV) traction motor are being extensively researched because of its high energy density and high efficiency. The traction motor for EV requires high power and high efficiency at the wide driving region. Therefore, it is essential to fully consider the characteristics of the motor from low speed to high-speed driving regions. Especially, when the motor is driven at high speed, a significant centrifugal force is applied to the rotor. Thus, the rotor must be stably structured and be fully endured at the critical speed. In this paper, aims to examine the characteristics of the IPM motor by adjusting the width of air-barrier according to the permanent magnet position which is critical in designing an IPM motor for EV traction motors and to conduct a centrifugal force analysis for grasping mechanical safety.

Separation of magnetic microparticles in segmented flow using asymmetric splitting regimes

A magnetic microparticle-based bioassay requires the separation of the microparticles from the sample matrix, after the microparticles have specifically captured the target of interest. For the implementation of such an assay in water-in-oil droplet segmented flow microfluidics, the particles must be separated from the aqueous sample droplets during a purification step. Current magnetic separation methods pose limits to purification, as only a limited part of the sample volume is removed in the purification step. Combining asymmetric droplet splitting in a T-junction-shaped microfluidic channel with magnetic separation, as induced by a permanent magnet positioned close to the microfluidic channel, is a promising and elegant solution for extracting the magnetic microparticles. However, retaining a high separation efficiency is a challenge and yet untried. In this paper, we describe a microfluidic and magnetic setup to separate superparamagnetic microparticles from the sample droplets, removing up to 90 % of the original sample volume in a single purification step, while keeping the separation efficiency constant. First, the conditions for particle aggregation, attraction and immobilization are determined and used to predict good separation conditions. Second, the magnetic forces at the splitting zone on the microfluidic chip are simulated for different permanent magnet positions and orientations; hereafter, the most promising setups are experimentally realized in polydimethylsiloxane microchannels, tested and the results considering different splitting regimes compared.

Analysis on the Charateristics of Variable Reluctance Resolver Considering Uneven Magnetic Fields

Variable reluctance (VR) resolver is widely used in traction motor for battery-powered electric vehicles (EVs), as well as for hybrid EVs as rotor position sensor. VR resolver generates absolute position signal using resolver-to-digital converter (RDC) to deliver the exact position of permanent magnets in the rotor of a traction motor to the motor controller. This paper deals with analysis methodology on a VR resolver using cosimulation analysis with RDC tracking algorithm for position-angle detection considering uneven magnetic fields. The eccentricity of the VR resolver, short-circuit conditions of the excitation and output-signal coils, and shape of rotor saliency are considered as sources of uneven magnetic fields in the VR resolver. Two-dimensional FEM is used for the SIN and COS output-signal waveforms, and these waveforms are converted into absolute position angle using RDC algorithm. To verify the analysis results of the proposed resolver, experiments on different uneven magnetic field conditions were conducted and compared with the simulation results.

Vibration and Noise in a HDD Spindle Motor Arising from the Axial UMF Ripple

We investigated numerically the characteristics of axial unbalanced magnetic force (UMF) due to axial magnetic design in the spindle motor of a hard disk drive (HDD). The HDD spindle motor has a magnet-overhang and a pulling plate to generate the axial magnetic force, which is applied to the fluid dynamic bearings (FDBs) as a preload in order to increase the axial stiffness of the HDD spindle system. However, the axial UMF ripple with the least common multiple (LCM) harmonics of pole and slot is generated by the pulling plate and magnet-overhang in the HDD spindle motor. We also investigated the characteristics of the axial magnetic forces generated in the pulling plate and the stator core, separately. We found that the axial magnetic forces generated in the pulling plate and the stator core have opposite phases. Furthermore, we proposed an optimal position of permanent magnet with respect to the stator core. We experimentally verified that the LCM harmonics of pole and slot in the vibration and acoustic noise mostly originate from axial UMF ripple and that the proposed design can effectively minimize the LCM harmonics in the vibration and acoustic noise of HDD systems.

Magnetic core shell nanoparticles trapping in a microdevice generating high magnetic gradient

Magnetic core shell nanoparticles (MCSNPs) 30 nm diameter with a magnetic weight of 10% are usually much too small to be trapped in microfluidic systems using classical external magnets. Here, a simple microchip for efficient MCSNPs trapping and release is presented. It comprises a bed of micrometric iron beads (6-8 μm diameter) packed in a microchannel against a physical restriction and presenting a low dead volume of 0.8 nL. These beads of high magnetic permeability are used to focus magnetic field lines from an external permanent magnet and generate local high magnetic gradients. The nanoparticles magnetic trap has been characterised both by numerical simulations and fluorescent MCSNPs imaging. Numerical simulations have been performed to map both the magnetic flux density and the magnetic force, and showed that MCSNPs are preferentially trapped at the iron bead magnetic poles where the magnetic force is increased by 3 orders of magnitude. The trapping efficiency was experimentally determined using fluorescent MCSNPs for different flow rates, different iron beads and permanent magnet positions. At a flow rate of 100 μL h(-1), the nanoparticles trapping/release can be achieved within 20 s with a preconcentration factor of 4000.

Prediction of cogging torque level in PM motors due to assembly tolerances in mass‐production

Purpose – The purpose of this study is to estimate the sensitivity of cogging torque in permanent magnet (PM) motor designs due to PM assembly tolerance and/or PM imperfections and to evaluate how such faults can be reliably detected in simulated and measured cogging torque signals.Design/methodology/approach – PM motors exhibit inherent cogging torque, which creates torque ripple and prevents smooth rotation of the rotor, resulting in undesirable vibration and noise. While cogging torque minimization is necessary to improve PM motor performance, several FEM models have been developed to study and present data demonstrating the sensitivity of cogging torque to PM assemblies and/or PM imperfections. Some procedures that would predict and evaluate cogging torque components relative to measured PM positions on assembled PM motors were proposed.Findings – On the basis of numerous performed simulations using different FEM models and experimental results on rotors from mass‐production, it was found and proved t...

Continuous range of stable equilibrium positions in the system of magnet and high- Tc superconductor

Experimental and theoretical studies of macroscopic dynamics of the system of permanent magnet (PM) and YBa 2Cu 3O 7 high- T c superconductor (SC) are made. Continuous ranges of PM and SC mutual positions are established of which all can realize stable equilibrium. Small oscillations about any such equilibrium point are investigated.