Edge Of Magnet Research Articles

The Application of Magnet Structures to Reduce the Cogging Torque Associated with Fractional Slot Number in Permanent Magnet Generators

This study proposes the application of a magnet structure to minimize the cogging torque (CT) and unstable pull in endless magnet generators. The investigation was conducted using an integral slot number of 24 slots and 10 poles, as well as a fractional slot number of 18 slots and 8 poles. The purpose of combining the multi-slot mechanism with pole arc optimization at the magnet edge was to underestimate the peak CT through a reduction in the quantity of tangential flux density. However, the results indicate that CT did not decrease significantly using this method, and this led to the optimization of the edge shape in the magnet structure through the introduction of the surface response method. The combination method’s goal was to ensure a significant reduction in both the integral and fractional slot numbers of the permanent magnet generator. The results show that the CT in the structure with an integral slot number of 24 slots and 10 poles decreased to around 99.4% compared with the baseline structure, while the CT in the structure with a fractional slot number of 18 slots and 8 poles was minimized to 98.8%. This led to the conclusion that the techniques could be combined in structure with any number of integral and fractional slots to reduce CT.

Effect of Combining of Shaping at Magnet Edge and Dummy Slotting at Stator Core on the Cogging Torque Reduction in Permanent Magnet Generator

Effect of combining the shaping at magnet edge and dummy slotting at stator on the cogging torque reduction in permanent magnet generator was studied. The cogging torque is the most issues in permanent magnet generator application, since it effects to reduce the generator performance. A permanent magnet generator with 24 slots and 20 poles structure is presented. For purpose of study, in the beginning the permanent magnet generator with conventional structure has been investigated as the basic reference of initial structure. In order to improve the performance of the permanent magnet generator, the magnet edge was shaped but the stator core is kept remain conventional structure. It can be found that the magnet edge effects to inprove a little bit of the performance of the permanent magnet generator. In the next investigation, the magnet edge slotting and dummy slotting in stator core of the permanent magnet generator was combined. Using the FEMM 4.2, the cogging torque value of the proposed of permanent magnet generator were analysed and compared. It was found that cogging torque reduction of the permanent magnet generator with combining the dummy slotting at stator core and magnet edge shaping can reduce the cogging torque from 0.0028554 N.m (intial base line) to 0.0000165 N.m (proposed model). In other word, the cogging torque can be to around 99.42 % compared with the base line. The magnet flux density at core of the permanent magnet generator proposed can be reduced to 35 %.

Soft magnetostrictive patches for guided wave ultrasonics using Wiedemann effect-based MPTs and EMATs

Magnetically soft and malleable magnetostrictive (MS) alloys are highly promising as low-cost solutions for high-efficiency generation of guided waves in industrial applications and a variety of magnetostrictive patch transducers (MPTs) have been described in the literature. This work focuses on understanding the mechanisms and behaviour of soft MPTs used in the Wiedemann effect geometry, generating shear horizontal (SH) guided waves using FeCo alloy patches. MPT operation is explored in relation to patch geometry, size, magnetic field directions and guided wave wavelength. MPTs are compared with electromagnetic acoustic transducers (EMATs) and EMATs are also placed on MS and copper foil patches bonded to large glass plates for some of the measurements. Periodic permanent magnet (PPM) array EMATs operating on MPTs bonded to ferritic steel samples produced significant enhancements in the generated wave amplitude and the detected signal amplitude when compared to directly generating on the steel substrate, which primarily operates through the Lorentz mechanism. This enhanced performance was investigated and was found to be due to the magnetic fringing fields at the magnet edges. Moreover, EMAT lift-off behaviour was significantly improved when an EMAT was placed above a magnetostrictive patch, with 50 mm lift-off between the EMAT and the patch demonstrated for SH wave generation at a 22 mm nominal wavelength at a 170 kHz excitation frequency on a glass plate sample.

Effect of Electrode–Normal Magnetic Field on the Motion of Hydrogen Bubbles

In comparison to alternative methods for hydrogen production, water electrolysis stands out as the optimal means for obtaining ultra-pure hydrogen. However, its widespread adoption is significantly hampered by its low energy efficiency. It has been established that the introduction of an external magnetic field can mitigate energy consumption, consequently enhancing electrolysis efficiency. While much of the research has revealed that an electrode–parallel magnetic field plays a crucial role in enhancing the bubble detachment process, there has been limited exploration of the effect of electrode–normal magnetic fields. In this work, we compare the water electrolysis efficiency of a circular electrode subjected to electrode–normal magnetic field resulting in a magnet edge effect and electrode edge effect by varying the sizes of the magnet and electrode. The findings indicate that a rotational flow caused by the Lorentz force facilitates the detachment of the hydrogen from the electrode surface. However, the rotation direction of hydrogen gas bubbles generated by the magnet edge effect is opposite to that of electrode edge effect. Furthermore, the magnet edge effect has more significant influence on the hydrogen bubbles’ locomotion than the electrode edge effect. With an electrode gap of 30 mm, employing the magnet edge effect generated by a single magnet leads to an average of 4.9% increase in current density. On the other hand, the multiple magnet effects created by multiple small magnets under the electrode can further result in an average 6.6% increase in current density. Nevertheless, at an electrode spacing of 50 mm, neither the magnet edge effect nor the electrode edge effect demonstrates a notable enhancement in conductivity. In reality, the electrode edge effect even leads to a reduction in conductivity.

Declining Cogging Torque Technique of an Integral Slot Number for Permanent Magnet Machines

The existence of cogging torque in electric equipment has been considered undesirable. This kind of friction in the air-gap impacts the alignment of flux and the stator slots, resulting in the observed outcome. Consequently, the imposition of restrictions on the rotation of the rotor is employed to generate electrical energy. This research endeavor primarily aims to mitigate the cogging torque of electrical machinery. The current utilization involves employing a total of 3 permanent magnet synchronous machines, often known as inset PMMs, which possess a slot count of 24 and a pole count of 8. The employed technique involves the integration of an optimal pole arc method in conjunction with the implementation of slots cut into the magnet's edge. The machine model under investigation has two fundamental variants, namely Models 1 and 2. These models are equipped with 1one-step slotted (OSS) and 2two-step slotted (TSS) edges on each magnet, in addition to pole arc optimization. The simulation was conducted using the Finite Element Method Magnetics (FEMM) 4.2 software together with LUA scripts, with a focus on rotor rotation ranges of 1 degree. Model 2 exhibited a decrease in cogging torque of 0.01 Nm, whereas Model 1 demonstrated a reduction of 0.015 Nm, and the basic model had a decrease of 0.02 Nm. When implementing a dual-layered cutting edge on a magnet and attempting to optimize its pole arc, it is imperative to consider that the cogging torque's peak magnitude becomes substantially diminished or entirely eliminated.

Computational analysis of conductive fluid flow with tangential components of magnetic flux density and electric field in metallic and non-metallic circular pipe

This paper has focused on the study of flow characteristics of a steady conductive fluid through a circular pipe in the presence of an applied transverse uniform magnetic field. A numerical simulation of the fluid flow was performed using a multi-physics computational tool. The radial velocity distribution due to the effect of the tangential component of induced magnetic flux density and electric fields at various axial positions is examined in metallic and non-metallic surfaces of the circular pipe. This simulation study helps to analyse the effect of drag force on the variation in axial velocity close to the metallic and non-metallic walls. The induced electric potential is directed along the normal to the Laplacian tangential surface of the pipe. In addition to that, sigmoidal-shaped field profiles are observed when the fluid flow crosses from the upstream to downstream of the magnet edge and vice versa along the axial length of the circular pipe. Simultaneously, it is observed that the average velocity of the fluid flow decreases for a laminar and increases for turbulent Reynolds number. Streamline plots pertinent flow variable such as flow velocity are presented for non-conducting and conducting walls.

Investigation Cogging Torque of PMM with rotor and Stator optimization for renewable energy application

This paper proposes the cogging torque reduction by using the optimization of the slotting method on the stator and the cutting edge of the rotor side magnet of the Permanent Magnet Machiene (PMM), of the Synchrounous Generator (PMSG). Here, the effect on the cross-sectional area of the magnetic poles and the additional width of the slot opening will lead to an improvement in the reduction of cogging torque for the investigated of the machine. The proposed machine has 6 poles and 18 slots with a fixed slot opening widths on the stator and modified magnetic poles on the rotor. The software used to investigate and analyze the saturation of the induced cores in the stator and rotor of machine is the magnetic finite element method (FEMM 4.2). The most cost-effective method to minimize the presence of cogging torque of any PMSG is to conduct the modification of the rotor where the magnets are located and modify the stator structure despite the complexity and cost of manufacturing the stator. Here, the cutting of magnetic edge structure using a simple cutting method is implemented. This is a different method from that already widely implemented for cutting the edge of the magnet surface. The simulation results show that the PMSG cogging torque by cutting the magnetic edge and adding a dummy slot can significantly minimize the cogging torque. It is found that the cogging torque reduction is 99.47 percent. This condition as the low cogging torque and low PMG speed can be used for reference design and PMSG construction for renewable energy plants such as in geothermal power plants.

MAGNETOTHERMAL CONVECTION ON THE THERMALLY STRATIFIED FLUID LAYER BY PERMANENT MAGNETS

Magnetothermal convection can be induced in paramagnetic fluid by temperature differences and the magnetic field. In this study, convection was studied both experimentally and numerically for the thermally stratified fluid layer attained by heating the top wall and cooling the bottom wall. When a single block magnet was placed above the top hot wall, convection was confirmed near the magnet edges. In the case of multiple magnets with alternating magnetic poles, convection was observed near the magnet junction(s) since the local magnetic force became stronger than that at the magnet edges. This effect depended on the number of magnets. A pair of block magnets with one junction induced a pair of vortex flows, in which the the local Nusselt number reached its maximum. In the case of three magnets, the two maxima of the local Nusselt number near the magnet junctions became smaller than that obtained in the two-magnet case. This was due to the weakened magnetothermal force that occurred by shifting the low-temperature region outward below the magnet junctions.

Cross talks between storage ring magnets at the Extremely Brilliant Source at the European Synchrotron Radiation Facility

Significant magnetic cross talks were observed between neighboring magnets on the Extremely Brilliant Source (EBS) low emittance storage ring. The main sources for these cross talks are the short longitudinal distances between magnets, which reach 47 mm in some cases. It affects mainly the dipole bending angles and the quadrupole gradients. A 1% bending angle correction was applied to the (permanent) bending magnets before their installation in the storage ring to compensate for the cross talks, while gradient errors as high as 1.8% were observed on quadrupoles. Intensive 3D magnetic simulations gave the longitudinal distribution of the cross talk errors for various magnet pairs and current settings. The error distribution depends on the magnet pairs: cross talks may create errors at magnet edges or all along the magnets, with same or opposite polarity. The simulations were validated by magnetic measurements, the discrepancies between measured and simulated values being in the ${10}^{\ensuremath{-}4}$ range with respect to the nominal gradients. Cross talk induced gradient errors were added to all quadrupoles and neighboring magnets in the lattice model. Even if it complicated the commissioning, the cross talks have no impact on the final performances of the lattice as the design machine parameters were reached for the most part.

Two-Steps Slotting Method in Magnet Edge of PMG for Wind Energy Harvesting

Two-Steps Slotting Method in Magnet Edge of PMG for Wind Energy Harvesting

Numerical and experimental study of influence function in magnetorheological finishing of oxygen-free high conductivity (OFHC) copper

Study of influence function of finishing process is very important for setting the process parameters. In this article, influence function of magnetorheological finishing (MRF) process is investigated numerically and experimentally by studying the flow behaviour of magnetorheological (MR) fluid. A 3D computational fluid dynamics simulation is performed considering MR fluid as a Herschel–Bulkley fluid. Dynamic pressure and wall shear stress on the workpiece surface are determined for different working gaps and rotational speeds. Variable depth of indentation by abrasive particle on oxygen-free high conductivity copper is calculated numerically and correlated with the experiments. Depth and area of influence function increase with spindle speed and reducing working gap. Dynamic pressure decides the indentation depth which is related to normal force, whereas wall shear stress removes the material up to the indentation depth which is related to the tangential force. Influence function shows two separate regions at the edge of magnet due to variable magnetic flux density. Contact length of MR fluid with workpiece and squeezing of MR fluid play significant role in material removal. Experiments are carried out to study forces acting on the workpiece, indentation depth and validation of simulation results.

A New Technique to Reduce the Cogging Torque of Integral Slot Number in Permanent Magnet Synchronous Machine

This paper proposed a new cogging torque reduction technique of integral slot number in the permanent magnet synchronous machine (PMSM). The purpose of the proposed new technique simulated on the PMSM with 48 slot/6 pole structure. In the study, the magnet edge of the PMSM was slotted to minimize the cogging torque while the stator core has remained natural. Slotting in magnet edge is one of the techniques to reduce the cogging torque in PMSMs, which has been existed in the previous research. In the proposed structure, we employed the two steps of slotting in magnets edge as one of the cogging torque reduction techniques. In this paper, authors have investigated three permanent magnet synchronous machine with different magnet structure has been studied and compared. The proposed permanent magnet synchronous machine with employed two steps of slotting has shown to promise the best of cogging torque reduction. The performance of the permanent magnet synchronous machine studied has been computed and analyzed by finite element analysis. It is found that the smaller cross-section area of magnet pole results in the decrement of cogging torque and air gap normal flux density in the PMSM. The new slotting in the magnet edge reduces the magnet pole cross-section and the cogging torque. The cogging torque of the proposed structure could be reduced around 98.8 % compared with the initial structure. The two steps of slotting could reduce the cogging torque of integral slot number in permanent magnet synchronous machine significantly.

Novel of Cogging Torque Reduction Technique for Permanent Magnet Generator by Compounding of Magnet Edge Shaping and Dummy Slotting in Stator Core

This paper dealt with the investigation and implementation of the cogging torque reduction technique in permanent magnet generators with a fractional slot stator/rotor combination of 24 slot/18 pole structure. A novel of cogging torque technique in a permanent magnet generator was developed and proposed in the paper. In the study, the cogging torque reduction technique was based on the compounding of two cogging torque reduction techniques, i.e., the magnet edge shaping with dummy slotting in the stator core of the fractional slot number. By employing the CT reduction technique proposed, effects on the decreasing of tangential flux density in the air gap of the permanent magnet generator, while the normal flux density almost remained constant. The tangential flux density is one important parameter regarding the peak of cogging torque in permanent magnet generator or other electrical machine structure. The normal and tangential flux have been analyzed. The cogging torque of the permanent magnet generator was analyzed and presented in the paper. By compounding both cogging torque reduction techniques, i.e., magnet edge shaping and dummy slotting in stator teeth have been expected to achieve the cogging torque reduction. The electromagnetic performance of the permanent magnet generator was performed using a finite element analysis of FEMM 4.2. It has been proved that by combining of magnet edge shaping and dummy slotting in stator teeth can reduce the cogging torque of permanent magnet generator significantly. It has been found that the cogging torque reduction for the proposed structure around 98.08 % compared with the initial structure.

High-precision magnetic field measurement and mapping of the LEReC 180° bending magnet using very low field NMR with Hall combined probe (140−350 G)

The relativistic heavy ion collider (RHIC) at BNL uses low-energy RHIC electron cooling (LEReC) to conduct experiments to search for the quantum chromodynamic critical point. The first ever electron cooling based on the RF acceleration of electron beams was experimentally demonstrated on April 5, 2019 using LEReC at BNL. The first critical step in obtaining successful 3D non-magnetized cooling of the Au ion bunches in the RHIC cooling section was matching the electron beam energy with a relative error less than 5 × 10−4 to the ion beam energy. Part of the LEReC beamline is a dipole magnet that bends the electron beam 180°. One of the most outstanding measurement challenges is that the dipole field is so low (≈200 G). Most of the existing NMR probes can only measure fields >400 G. A lower signal-to-noise ratio at low fields requires the use of larger sample volumes. Working with CAYLAR, the NMR probe has been redesigned and optimized for these low field measurements with high resolution. We report the methods, challenges and results for extensive magnetic field mappings of the 180° dipole magnet. A combination of NMR and Hall sensors was successfully implemented to measure uniform field regimes inside the magnet center area and non-uniform field regimes at the magnet ends. Detailed measurement and mapping were performed at five radii and five heights along the beam trajectory. Meanwhile, a finite element magnetic modeling simulation of the magnet using Opera software was performed. The calculated and measured data were compared, and the calculated data are a good reference for the measured data over long length mapping from the magnet edge to the center. The measured magnetic measurement data are directly useful for beam instrumentation, diagnostics and operation.

Study of The Effect of Height and Length of Slotting in Magnet Edge on the Cogging Torque Reduction of Fractional Slot Number in Permanent Magnet Machine

Cogging torque generated in permanent magnet machine effects to some undesirable vibration and noises. In order to minimize the cogging torque in permanent magnet is the most important issues recently. This paper investigated the influence of the value of height and length of slotting in magnet edge on the cogging torque reduction. For purpose of study the structure of 24 slot/10 pole of permanent magnet machines have been chosen. The 2-D finite element based on FEMM 4.2 software was implemented to compute the permanent magnet machine performance. Simulation results showed that by optimising the height and length of slotting in magnet edge can reduce the cogging torque of permanent magnet machine significantly. The most effective way by employing a-two step slotting with 2.5 mm of height and 0.7 mm of length of the slotting in magnet in the first step of slotting. In the second step of in magnet edge, the length of slotting has been assigned as much as 2.3 mm and the height of slotting was 0.588635 mm. By employing the FEMM, three of different magnet structures of permanent magnet machine were analysed. It was found that the cogging torque of permanent magnet machine proposed magnet structure as much as 99.7 % compared with the initial structure of the permanent magnet machine.

Study the Influence of Edge Points of Magnet Surface and Stator Core on the Cogging Torque Reduction in Permanent Magnet Machine

Cogging torque in permanent magnet machine application effects to some undesirable vibration and noises. To minimize the cogging torque in permanent magnet machine’s the most important issue recently. Influence the number of edge points in the magnet of one and two steps of magnet edge slotting was studied in this paper’. For purpose of study, the structure of permanent magnet machine with 18 slot / 8 pole has been chosen, and the magnetic flux of all magnets was radial. The finite element of 2D based on FEMM 4.2 software was implemented to analysis the magnet flux distribution in air gap. Simulation results showed that by improvement of edge point at magnet edge of the two steps of slotting in magnet edge could reduce the cogging torque of permanent magnet significantly when compared with the initial structure. Employing the numerical simulation, both of the machine structures were analysed. It has been found that, the cogging torque reduction of edge points with 8 points has the highest reduction around 98.84 % compared with initial structure of the permanent magnet machine.

Study the Effect of Dummy Slot in Stator and Rotor on the Cogging Torque Reduction in Permanent Magnet Machine

In this study, the effect of dummy slot in stator core and magnet in rotor core greatly affects the value of the cogging torque reduction in permanent magnet machine. The structure of permanent magnet machine was analysed employed finite element based on the finite element method magnetic (2D). In this study, 4 type of permanent magnet machine structure has been analysed. Permanent magnet machine structure in rotor have 4 type design magnet, permanent magnet machine with initial structure magnet, bread loaf, magnet edge slotting, and magnet edge slotting-magnet slot of surface. The cogging torque reduction of the proposed permanent magnet machine were computed and compared with the initial structure. Using the finite element, authors have computed and found that the cogging torque reduction of type 3 and type 1. The cogging torque of proposed permanent magnet machine could be reduced to 97.17% by employing the dummy slot in stator core.

Study the Effect of Combination of Shoe Height and Slot Opening width to Reduce Cogging Torque in Permanent Magnet Generator

Cogging torque is one important problem in a permanent magnet generator. With a good understanding of the phenomenon, the cogging torque can be minimized by using the multi-objective technique. This paper presents a combination technique for cogging torque reduction by an appropriate small stator slot opening width, stator shoe height with fractional technique in Permanent Magnet Generator. Cogging torque waveforms, along with other relevant characteristics are investigated in this research and by analysis using the finite element method, the combination width shoe height and magnet edge slotting effect to decline the cogging torque peak value. A significant value of cogging torque, when slot opening width of 1.55 mm and shoe height of 2.3 mm, provide the peak value of cogging torque in the structure is 0.00062 N-m for positive value and about -0.00064 N-m for the negative value. It can be concluded that this type of slot opening width of 1.55 mm and shoe height of 2.3 mm is the best structure of the fractional 8 slot, because it has any significant low of cogging torque and least of unbalance magnetic pull

Improvement of Cogging Torque Reduction by Combining the Magnet Edge Shaping and Dummy Slot in Stator Core of Fractional Slot Number in Permanent Magnet Machine

A new technique in reducing the cogging torque by combining the magnet edge shaping and dummy slot in stator core of fractional slot number in permanent magnet machine was studied in this paper. The cogging torque is the most issue in permanent magnet application, since it effects to reduce the machine performance. A permanent magnet machine of fractional slot number with 24 slot/20 pole was presented in the paper. Firstly, the permanent magnet machine with conventional both of magnet structure and stator structure has been investigated as the basic reference of initial structure. Secondly, the magnet edge shaping with conventional stator core was investigated. Thirdly, in proposed structure, the combination of magnet edge shaping with dummy slot in stator was employed. The three different structures of the permanent magnet machine then analysed and compared. By implementation of magnet edge shaping combined with dummy slot in stator core has increased the interaction between magnet and stator core. This leads to increase the cogging torque frequency and reduce the peak value the cogging torque of the machine. Using the FEMM, the cogging torque value of the permanent magnet machine was analysed and computed. It was found that cogging torque reduction of the proposed structure as much as 99.47 % compared with the initial structure.

Natural convection of paramagnetic fluid along a vertical heated wall under a magnetic field from a single permanent magnet

The natural convection of a paramagnetic fluid is numerically investigated in the presence of a magnetic field from a block permanent magnet. One vertical wall of a cavity is partially heated at a constant heat flux to consider a single vertical heated wall. The permanent block magnet is placed behind the heated wall, of which the magnetic field is numerically obtained. Since the magnetic force is remarkable at edges of the block magnet, the magnetothermal force is also pronounced if the temperature difference exists by wall heating. The overlapping magnetothermal force works to repel the fluid. This results in the heat transfer enhancement near the upper magnet edge, and suppression near the lower magnet edge. The suppressing effect becomes remarkable rather than the enhancing one in cases of large magnetic induction, high wall heat flux, and high magnet elevation to the heated wall.