Single Permanent Magnet Research Articles

A Numerical Calculation Model of Multi-Magnet-Array and 8-Shaped Null-Flux Coil for Permanent Magnet EDS Vehicle System

Inspired by the superconducting electrodynamic suspension (EDS) system in Japan, a new permanent magnet (PM) EDS system combining PM and 8-shaped null-flux coils has emerged in recent years. In general, the structure of a single PM was used as the onboard magnet. This single magnet structure is difficult to further optimize the core magnetic field resource of the EDS system. Facing this issue, we proposed a PM EDS system combining a Halbach PM array (HPMA) with good magnetic collecting capability and the 8-shaped null-flux coils. Furthermore, we established a numerical model for this new HPMA EDS system. The core of the calculation method is to discretize each PM in the HPMA into a coil group. By calculating the mutual inductance between the equivalent coil groups and the null-flux coils, the interaction electromagnetic force is obtained. In order to verify the correctness of our numerical model, the calculation results of the finite-element method (FEM) simulation model are compared with those of the numerical model. The results of two models are basically consistent. It shows that the numerical calculation model has high accuracy. On this basis, the effects of various parameters on three main electromagnetic forces are studied to better explore the application characteristics of the HPMA EDS system. To sum up, this established numerical model can effectively avoid the calculation error caused by the edge effect of the discontinuous magnet array. It provides an accurate calculation method for the optimization of the EDS system combining the PM array and the null-flux coils.

Comparative Study on Torque Performance of Five-phase Single-Stator and Double-Stator Permanent Magnet Synchronous Motors

This paper compares the torque characteristics of single stator permanent magnet synchronous motor(PMSM) and double-stator PMSM under different split-ratios, air-gap lengths and shaft diameters by finite element method. Firstly, the effects of split-ratio towards the torque characteristics of the two motor structures under different air-gap lengths are researched, the results show that the optimal split-ratios of the two motor structures do not change under different air-gap lengths, and the optimal split-ratio of the double-stator motor is greater than that of single-stator, and the torque of the double-stator motor is greater than that of single-stator motor with arbitrary split-ratio under the same air-gap length; Finally, the effects of the shaft diameter to the torque of the two motor structures are investigated, obtaining that with the increasing of shaft diameter, the electromagnetic torque of the single-stator motor is almost unchanged, however, the torque of the double-stator is gradually reduced, when the shaft diameter reached a certain extent, the electromagnetic torque of the double-stator motor is smaller than that of single-stator motor with the split ratio within a certain range, and the torque/quality ratio of the double-stator motor is smaller than that of single-stator motor with their optimal split ratio separately.

Iron Loss Analysis in Axial Flux Permanent Magnet Synchronous Motors With Soft Magnetic Composite Core Material

Accurate calculation of iron losses in electric machines are essential for optimal machine design. This is especially important for axial flux permanent magnet motors with solid stator and rotor cores. This paper investigates iron losses in axial flux motor with soft magnetic composite material for the stator and the rotor. First, an analytical model is proposed to estimate iron losses under different operating conditions. The model is based on combining the Quasi 3-D computation approach and the magnetic equivalent circuit. The proposed model can be modified to account for different motor topologies and different stator and magnet designs. Then, The effect of torque ripple, on iron losses, is studied by comparing two motors: an optimized motor, with dummy pocket added to the stator tooth, and a non-optimized motor. Finally, the effect of the motor control scheme and the inverter switching frequency is studied by implementing two controllers: the Field Oriented Control and the Trapezoidal control. Simulations using 3-D finite element analysis and experimental tests are conducted, under different operating conditions, on two <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{12}\,V$</tex-math></inline-formula> , 6 slots, 8 poles single stator single rotor fractional horsepower axial flux permanent magnet synchronous motor prototypes. Test results shows that motor optimization, the choice of the motor control scheme, and the selected switching frequency can significantly affect iron losses in the motor. Using an optimized motor with a smooth control scheme, such as Field Oriented Control, and a high switching frequency, can cause a variation in iron losses by around 14% compared to a non optimized motor with the Trapezoidal control and a low switching frequency.

Transient Analysis Method of an Axially Magnetized Novel Passive Eddy Current Damper for Suppressing Lateral Vibrations

A passive eddy current damper (PECD) can be adopted to provide a damping effect and drag force in rotating structure applications. The damping effect is formed as the result of induced eddy current, while the drag force is produced as the result of the repulsive force between the same axially poled magnets. However, modeling and approximating the damping effect, repulsive force, stiffness, the magnetic flux density (MFD) distribution, and eddy current prompted in PECD is a challenging task because of the complicated structure and operational conditions. This paper presents a new method for modeling and estimating the dynamic parameters of novel PECDs such as the damping effect, repulsive force, and stiffness for suppressing vibration in rotating structure applications. This self-powered, cost-effective PECD utilizes four arc-shaped and single ring-shaped permanent magnets with a cylindrical conductor placed between the arc magnets and the ring magnet to generate a damping effect and spring. Eddy currents are generated in the cylindrical conductor as the effect of the relative motion of the ring magnet concerning the arc magnets. An accurate and transient analysis method of the proposed system is carried out by using a three-dimensional finite-element method (3D-FEM). According to the procedures applied in the FE model solution, this new numerical method is appropriate and validated for analyzing PECDs and gaining good results by configuring the conductor and permanent magnets symmetrically. Finally, this novel 3D transient analysis method presents a perfect ability and accuracy for both modeling and calculating the PECD parameters.

Shaping the topology of a single phase BLDC motor for reduced cogging torque and improved performance

In the paper is presented a step-by-step development of the topology for a novel single phase permanent magnet (PM) brushless DC (BLDC) motor, aiming to improve its operation with more efficient utilisation of the active materials. The studied motor is based on a generic design, where asymmetrical stator poles and respective shaping of the permanent magnets is applied. Accurate 2D finite element simulations were employed for numerical prototyping of the motor design, until the expected results were obtained. Based on FEA, cogging and static torque waveforms, along with other relevant performance characteristics were determined and examined. The results show that the motor topology, and in particular, the detailed shape of the stator poles has the most important impact on the smooth operation of the single phase BLDC permanent magnet motor.

Süreksiz Referans Sinyalleri ile İnsan Sinovyal Sıvısında Birden Fazla Biyohibrit Mikrorobotun Hareket Kontrolü için Benzetim Çalışmaları

It is envisioned that biomedical swarms are going to be used for therapeutic operations in the future. The utilization of a single robot in live tissue is not practical because of the limited volume. In contrast, a large group of microrobots can deliver a useful amount of potent chemicals to the targeted tissue. In this simulation study, a trio of magnetotactic bacteria as a task-force, Magnetospirillum Gryphiswaldense MSR-1, is maneuvered via adaptive micro-motion control through an external magnetic field. The magnetic field is induced by a single permanent magnet positioned by an open kinematic chain. The coupled dynamics of this small group in the human synovial tissue is simulated with actual magnetic and fluidic properties of the synovial liquid. The common center of mass is tracked by the equation of motion. The overall hydrodynamic interaction amongst all three bacteria is modeled within a synovial medium confined with flat surfaces. A bilateral control scheme is implemented on top of this coupled model. The position of the common center of mass is used as the reference point to the end-effector of the robotic arm. The orientation of the magnetic field is rotated to change the heading of the bacterial-group in an addressable manner. It has been numerically observed that controlling the common swimming direction of multiple bacteria is fairly possible. Results are presented via the rigid-body motion of the robotic task-force as well as the fluidic and magnetic force-components acting on the bacteria along with the bilateral control effort in all axes.

Featured Cover

The cover image is based on the Review Article Single stator-single rotor permanent magnet Vernier machine topologies for direct-drive applications: Review and case study by Jawad Faiz et al., https://doi.org/10.1002/2050-7038.13240.

Design of a variable-gain adjacent cross-coupled controller for coordinated motion of multiple permanent magnet linear synchronous motors

Coordination position control of multi-motors systems is widely applied in agricultural and industrial fields that require high precision and synchronization among motors. Current adjacent cross-coupled control is unable to change the control gains as motor states are time-variant. The invariant gain compensation will inevitably weaken the coordinated control performance, especially in the presence of load disturbances. To solve this issue, this paper proposes a variable-gain adjacent cross-coupled controller. A sliding mode controller is adopted to cope with the disturbances and uncertainties for each single permanent magnet linear synchronous motor (PMLSM). The motor state of each PMLSM can be detected through system identification in real time. According to the motor states of the PMLSMs based on the system identification technique, a fuzzy position control algorithm is implemented for regulating the gain compensation. A consistent steady-state performance is subsequently maintained even with the existence of system uncertainties and load disturbances. It is proved from the experimental results that, compared with fixed-gain adjacent cross-coupled control scheme, the proposed controller has a better synchronization, a higher tracking accuracy and synergistic accuracy, under both no load and time-varying load conditions. For the variable-gain adjacent cross-coupled control, a position tracking error and a synergistic error within 7 μm and 8 μm can be achieved, respectively.

Electromagnetic‐Thermal Bi‐directional Coupling Analysis of IEF‐DDPMM Under Different Operation Conditions and Cooling System Optimization Design

Compared with the traditional single stator permanent magnet (PM) direct‐drive motor, the direct‐drive PM motor with inner enhance force (IEF‐DDPMM) has the advantages of high‐torque density, strong heavy‐load starting ability and flexible operation mode, so it is especially suitable for the occasions such as mine winches with a wide load range, frequent heavy‐load starting, light‐load operation, and limited use environment space. It is very important to check the temperature rise of IEF‐DDPMM according to its different operating conditions, including transient temperature rise during heavy‐load starting and steady‐state temperature rise during rated operation, so as to optimize the electromagnetic and thermal performance at the same time. Based on the bi‐directional coupling method (BDCM) of the electromagnetic field and temperature field, the thermal analysis of IEF‐DDPMM and the transient temperature field analysis of the inner motor as a torque motor for short‐term operation are carried out, and then the rated power of inner motor in S1 working system and the maximum operation time of output peak power are determined. The fluid–solid coupling analysis method is used to optimize the design of the cooling system, and the influence of the number of water channels and inlet water velocity on the heat dissipation effect of the motor is analyzed. A cooling system with strong heat dissipation ability is obtained, which can achieve higher power or torque output within the temperature range of winding insulation or demagnetization limitation of PM. Finally, a prototype is developed and equipped with a temperature rise experimental platform, and the experimental results provided a good verification of the simulation results. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Recovery of Magnetic Catalysts: Advanced Design for Process Intensification.

The design of microdevices in which components with magnetic character must be separated and recovered from reactive media benefits from the advantages of microfluidics and meets the criteria for process intensification; however, there are open questions, such as the design of the most appropriate magnet arrangement, that need further research in order to increase the magnetic gradient exerted on the particles. Herein, we focus on the continuous recovery of magnetic microparticles, that can be used as support to facilitate the recovery of biocatalysts (magnetic microcatalysts, MMCs) from biological fluids. We analyze and compare the performance of two typical magnetophoretic microdevices for addressing bead recovery: (i) annular channels with a quadrupole orientation of the permanent magnets (quadrupole magnetic sorter, QMS) and (ii) the standard design, which consists of rectangular channels with a single permanent magnet to generate the magnetic field. To this end, an experimentally validated computational fluid dynamics (CFD) numerical model has been employed. Our results reveal that for devices with the same width and length, the micro-QMS, in comparison to a rectangular channel, could accomplish the complete particle retrieval while (i) processing more than 4 times higher fluid velocities, treating more than 360 times higher flow rates or (ii) working with smaller particles, thus reducing by 55% the particle mass. Additionally, the parallel performance of ≈300 micro-QMSs fulfills the processing of flow rates as high as 200 L·h–1 while entirely capturing the magnetic beads. Thereby, this work shows the potential of the QMS advanced design in the intensification of the recovery of catalysts supports of magnetic character.

Real time display with the ferrolens of homogeneous magnetic fields

In our previous published research we have studied the applications of the ferrolens for the observation and qualitative analysis of non-homogeneous magnetic fields. Latest developments over the last few years of the ferrolens increased multifold the sensitivity of this device allowing it to display magnetic fields as low as 10mT in strength and therefore it is possible now to observe also the homogeneous (i.e. straight parallel magnetic flux lines of uniform density in space) magnetic field existing inside air solenoids and between N-S poles of two attracting separated permanent magnets. We present and analyze herein these novel observations of homogeneous magnetic fields with the ferrolens and as a potential new application of this device. The ferrolens can now display the projected magnetic field on air from a distance without needing to be in physical contact with the field source. Experiments were carried out to demonstrate these new capabilities of the ferrolens as a nanomagnetic flux viewer, real-time physical device and scientific qualitative tool. We compare the geometry of magnetic fields of condensed matter ferromagnets with that of magnetic fields inside electrical air solenoids. Specifically, the homogeneous field between two N-S attracting magnets at a distance as well as inside air solenoids and Helmholtz coils and also the non-homogeneous total field of single dipole permanent magnets were observed using a latest generation very sensitive ferrolens. The unique feature of this magneto optic fluid thin film physical device is that it can display discrete magnetic flux lines of the macroscopic field. Also we show how the ferrolens can be used to detect qualitatively the symmetry center of a non ideal homogeneous magnetic field.

On the modeling of amplitude-sensitive electron spin resonance (ESR) detection using voltage-controlled oscillator (VCO)-based ESR-on-a-chip detectors.

In this paper, we present an in-depth analysis of a voltage-controlled oscillator (VCO)-based sensing method for electron spin resonance (ESR) spectroscopy, which greatly simplifies the experimental setup compared to conventional detection schemes. In contrast to our previous oscillator-based ESR detectors, where the ESR signal was encoded in the oscillation frequency, in the amplitude-sensitive method, the ESR signal is sensed as a change of the oscillation amplitude of the VCO. Therefore, using VCO architecture with a built-in amplitude demodulation scheme, the experimental setup reduces to a single permanent magnet in combination with a few inexpensive electronic components. We present a theoretical analysis of the achievable limit of detection, which uses perturbation-theory-based VCO modeling for the signal and applies a stochastic averaging approach to obtain a closed-form expression for the noise floor. Additionally, the paper also introduces a numerical model suitable for simulating oscillator-based ESR experiments in a conventional circuit simulator environment. This model can be used to optimize sensor performance early on in the design phase. Finally, all presented models are verified against measured results from a prototype VCO operating at 14 inside a 0.5 magnetic field.

A method for optimizing electromagnetic ultrasonic probe based on the spatial distribution of permanent magnets

The external magnetic field of a single permanent magnet is modeled by the vector magnetic potential method based on the Ampere hypothesis, which is compared with the finite element method to analyze the external magnetic field of the permanent magnet. Based on this, the mathematical models of the external magnetic field of multiple permanent magnets are obtained. By analyzing the external magnetic field of the permanent magnet of an electromagnetic ultrasonic probe proposed in this paper, the influence of the parameters of the permanent magnet on the external magnetic field is studied. The optimized structure containing multiple permanent magnets can increase the vertical component of magnetic field strength by about 32.3% compared with that of a single permanent magnet.

An Energy-Harvesting System Using MPPT at Shock Absorber for Electric Vehicles

This paper investigates an energy-harvesting system that uses of vibration energy at a shock absorber for electric vehicles. This system mainly comprises a linear electromagnetic generator and synchronous buck converter. To obtain the electrical energy through a linear electromagnetic generator, the perturb and observe maximum power point tracking (P&amp;O MPPT) scheme is applied at the converter. The power converter circuit is designed with a diode rectifier and synchronous buck converter. The generated electric power is able to transmit to the battery and the damping force of the shock absorber is adjusted by the controlled current of generator. The linear electromagnetic generator was designed as a single phase eight-slot eight-pole tubular permanent magnet machine. The performance of the proposed energy-harvesting system was verified through simulations and experiments.

10 kW Optimization of grid-connected wind power system and its application in Xiamen

Coastal areas not only have large annual average wind speed, but also have more days of strong winds in a year. Xiamen >8 gale days, 22.4 days a year, so it is very suitable for wind power generation. This design is 10 kW wind grid-connected power generation system, each branch is composed of permanent magnet synchronous motor, rectifier, boost module, inverter and filter, 20 groups are used in parallel to form 10 kW system. Choose a single permanent magnet synchronous wind turbine power of 500 W, need 20. System DC voltage :12 V, when the power is fixed, the proper lifting of DC voltage is helpful to reduce the current, thus preventing the IGBT from causing device damage due to overcurrent. A two-dimensional fuzzy controller is used to select the outer loop error and error differential signal as input variables. In order to verify the correctness of fuzzy adaptive PI control strategy, a system simulation model is built.

Reduction of Cogging Torque in AFPM Machine Using Elliptical-Trapezoidal-Shaped Permanent Magnet

The reduction in cogging torque enables smooth operation and an increase in the torque density of the machine. This research aims to minimize cogging torque in dual rotor single stator axial flux permanent magnet (AFPM) machine. Reduction in cogging torque makes the back EMF sinusoidal and reduces the torque ripples in AFPM machine. In this paper, an elliptical trapezoidal-shaped permanent magnet (PM) is proposed to minimize torque ripples of the AFPM machine. The 3D finite element analysis (FEA) is used for the analysis of AFPM machine. The optimization of AFPM machine is done by employing the asymmetric magnet-overhang along with the parameters of elliptical-shaped PM using Genetic algorithm (GA).

A Novel Electromagnetic Flowmeter for Liquid Metal of Nuclear Reactors

Electromagnetic flowmeters (EMFM) play an important role in the cooling process of nuclear reactors, especially when the coolant is liquid metal. According to the working principle of the electromagnetic flowmeter, it is necessary to use a large-sized magnet to provide a uniform magnetic field, but this is very difficult for a core with limited space. This paper proposes a novel electromagnetic flowmeter with a single cylindrical permanent magnet. Compared with the conventional flowmeter, the volume of this electromagnetic flowmeter is greatly reduced. This paper perfects the theory of this single magnet flowmeter and compares it with the experimental results.

Excitation of Single-Mode Shear-Horizontal Guided Waves and Evaluation of Their Sensitivity to Very Shallow Crack-Like Defects

Inspection is a key part of the asset management process of industrial plants and there are numerous plate-like structures that require inspection. Ultrasonic guided waves have been extensively used to detect various types of defect by monitoring reflected and transmitted signals because they enable faster screening of large areas. However, ultrasonic guided wave testing becomes difficult for very shallow, sharp defects as current inspection techniques suffer from a lack of sensitivity to such features. Previous studies, obtained by comparing various inspection techniques, suggest that the SH1 mode in particular, at around 3 MHz · mm, would be suitable when testing for shallow defects; however, it is clear that both the SH0 and SH1 modes can exist at this frequency-thickness product. This can complicate the inspection process and, therefore, limit defect detectability. This article investigates the possibility of a single-mode excitation of the SH1 mode at around 3 MHz · mm. The ability of this method toward detecting very shallow defects (<10% cross-sectional thickness loss) has also been studied. By means of analytical predictions and finite element, it is shown that a signal dominated by the SH1 mode can be generated using a single permanent periodic magnet (PPM) electromagnetic acoustic transducer (EMAT) (PPM EMAT). All predictions are then backed up by experimental measurements. It is also shown that, by studying the reflection coefficient of the SH1 mode, the pure SH1 mode can be used to detect defects as shallow as 5% thickness loss from a 500-mm stand-off. These defects would otherwise be missed by standard, lower frequency guided wave testing.

A Novel Single-Phase Tubular Permanent Magnet Linear Generator

A novel single phase tubular permanent magnet linear generator (TPMLG) for Stirling engines is proposed in this paper. It has an outer-stator, an inner-stator, a mover and a bread type winding which has no cutting. The mover consists of four ring-shaped permanent magnets, all of which are polarized radially. The polarization direction of the outer two permanent magnets is opposite to that of the inner two to form more magnetic circuits and achieve higher power generation density. The polarized directions of the two adjacent permanent magnets of both the outside and inside are opposite. The structure, dimensional parameters and operation characteristics of the generator are illustrated in detail. One of the structural advantages of this generator is that it is easy to control. The 3-D finite element (FE) model of proposed TPMLG is established. The model and its boundary conditions are presented and explained in detail. Through the FE model, its electromagnetic analysis is carried out. The performance of this generator under reciprocating frequency 75 Hz is investigated and analyzed. The simulation results show that the generator has the advantages of high power density.

Temperature characteristics of bulk YBCO exposed to high frequency fluctuant magnetic field in high-TC superconducting maglev system

In high-temperature superconductor (HTS) Maglev system, the permanent magnet guideway (PMG) can't be formed by the whole permanent magnet (PM), which results in the existence of multiple PM splicing slots in the PMG. Moreover, this kind of splicing gap will become bigger with the longer service time of PMG. In addition, due to material inhomogeneity and magnetization difference inside a single PM and there will be fluctuation in magnetic field (MF) above PMG. The fluctuation may have a great impact on the efficient and stable operation of the Maglev system. This paper focuses on the influence of fluctuant MF on the temperature rise inside bulk HTS, including the internal loss caused by cooling height (CH), working height (WH) and frequency of MF change. Finally, the HTS Maglev system is analyzed from temperature rise inside the bulk HTS. The results and analyses of this article are useful for the application of bulk HTSs in the Maglev system.