Arrangement Of Permanent Magnets Research Articles

Comparative Study of Partitioned Stator Memory Machines With Series and Parallel Hybrid PM Configurations

In this paper, the partitioned stator (PS) structure is extended to variable-flux memory machines, forming two newly emerged PS switched-flux memory machines (PS-SFMMs) with series and parallel hybrid magnet configurations. From the perspective of geometry, both two PS-SFMMs share identical outer stator and rotor segments, while two different types of permanent magnet (PM) arrangements are employed in the inner stationary part. Thus, the developed machines can inherent the geometric separation of the armature winding and PM excitations from the PS design, thus achieving acceptable torque capability, and excellent air-gap flux control. A comparative study between PS-SFMMs with series and parallel structures is established. First, the topologies and operating principle are introduced, respectively. In addition, the design tradeoffs and PM sizing of the two PS machines are revealed and optimized with a simplified magnetic circuit model. Then, the electromagnetic characteristics of PS-SFMMs with different magnetic circuits are investigated and compared with the finite-element (FE) method. The FE results are validated by the experiments on a parallel prototype.

Comparative Study of Two Novel Double-Sided Hybrid-Excitation Flux-Reversal Linear Motors With Surface and Interior PM Arrangements

In this paper, two novel double-sided hybrid-excitation flux-reversal linear motors (DSHEFRLM) with the surface (S-) and interior (I-) permanent-magnet(PM) arrangements are proposed and comparatively investigated. The proposed motors feature an asymmetrical double-sided primary configuration which enables the armature and field excitations to be placed separately. Through 2-D finite-element method (FEM), two motor structures with different slot/pole combinations are optimized, and then, the magnetic fields and electromagnetic performances are calculated, including inductances, no-load flux linkage, thrust characteristics, and PM demagnetization capability. By comparison, it is found that S-DSHEFRLMs show larger thrust density while I-DSHEFRLMs exhibit superior flux-adjusting capability. Finally, these predicted results are validated by 3-D FEM.

Dual Resonator MEMS Magnetic Field Gradiometer.

Accurate knowledge of the spatial magnetic field distribution is necessary when measuring field gradients. Therefore, a MEMS magnetic field gradiometer is reported, consisting of two identical, but independent laterally oscillating masses on a single chip. The sensor is actuated by Lorentz force and read out by modulation of the light flux passing through stationary and moving arrays of the chip. This optical readout decouples the transducer from the electronic components. Both phase and intensity are recorded which reveals information about the uniformity of the magnetic field. The magnetic flux density is measured simultaneously at two points in space and the field gradient is evaluated locally. The sensor was characterised at ambient pressure by performing frequency and magnitude response measurements with coil and various different permanent magnet arrangements, resulting in a responsivity of 35.67 V/T and detection limit of 3.07 µT/ (@ 83 Hz ENBW). The sensor is compact, offers a large dynamic measurement range and can be of low-cost by using conventional MEMS batch fabrication technology.

Influence of Adjacent Teeth Magnet Polarities on the Performance of Flux Reversal Permanent Magnet Machine

This paper provides a comprehensive analysis of performance difference among various kinds of flux reversal permanent magnet (FRPM) machines having different permanent magnet (PM) arrangements. Four PM arrangement types are, first, identified by the number and relative polarities of PMs on the stator teeth, and their influence on the equivalent pole-pair number of the armature winding and working harmonics of the air-gap field is revealed. Then, the torque variation against the rotor pole number of each PM arrangement is analyzed. The electromagnetic performance of four PM arrangements with a 14-pole rotor is compared in detail. It shows that the FRPM machine, in which four PM pieces are mounted on each stator tooth and two adjacent magnets on different stator teeth are of opposite polarities, offers the highest torque density and the highest efficiency, which make it promising in low-speed high-torque applications. In addition, four prototype machines are manufactured and tested to validate the findings.

Influence of Shape and Arrangement of Permanent Magnets on Characteristics of Outer-Rotor IPM Motor

Influence of Shape and Arrangement of Permanent Magnets on Characteristics of Outer-Rotor IPM Motor

An Investigation Into the Effect of PM Arrangements on PMa-SynRM Performance

The paper aims to provide a guideline for rotor design of permanent magnet (PM) assisted synchronous reluctance machine (PMa-SynRM). Unlike interior PM machines, the PMa-SynRM is essentially an SynRM with dominant reluctance torque. The PMa-SynRM is often designed by directly embedding magnets into an SynRM rotor to improve the performance. However, how the PMs can be arranged in the rotor to enhance motor performance has not been fully discussed. This paper investigates the influence of several key factors concerning the PM arrangements, including number of PM layers, inserted positions, and PM sizes. The torque, flux linkages, power factor, and motor performance are comprehensively evaluated. Based on the analysis, a brief guideline is suggested for PMa-SynRM rotor design. Finite element analysis is used for evaluation and experiments are conducted to validate the analysis.

Comparative Study of Hybrid PM Memory Machines Having Single- and Dual-Stator Configurations

In this paper, the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations. Two types of permanent magnets (PMs), i.e., NdFeB and low coercive force PMs, are located in the stationary part. Thus, the developed machines can achieve easy online PM magnetization control, excellent air-gap flux control, and acceptable torque capability. In order to address the issue about the limited stator space encompassing dual PMs and magnetizing coils in the SS-SFMM, a DS design is further developed, where all excitations are placed on a separate inner stator to improve the torque density. A comparative study between the SFMMs with SS and DS structures is established. The investigated machine topologies and operating principle are described first based on a “U”-shaped hybrid PM arrangement, and the PM sizing of the DS machine is optimized with a simplified magnetic circuit model. In addition, the electromagnetic characteristics of the SFMMs with SS and DS structures are investigated and compared by a finite-element (FE) method. The FE results are validated by the experiments on two fabricated prototypes.

Analytical Performance Calculation of Vernier Hybrid Machine with Subdomain Method

The analytical subdomain models of vernier hybrid machines with two kinds of permanent magnet (PM) arrangements are developed, and the magnetic vector potentials are considered unknown variables to obtain the no-load and on-load magnetic field in this article. According to the electromagnetic properties and machine structure, the entire solving region is divided into five subdomains, namely the stator slot, slot opening, PM, air gap, and rotor slot. Using the general solutions of magnetic vector potentials and boundary conditions, the magnetic field distributions of all subdomains are obtained. Then the air gap flux density, flux linkage, back-EMF, cogging torque, electromagnetic torque, unbalanced magnetic pulls, and PM loss are calculated and compared for the two models. With the analytical model, the PM demagnetization withstand capacity, effects of main parameters on the torque ripple and average torque, and combinations of PM and rotor slot numbers are also studied. The 2D finite element method and experimental results of two prototype machines validate the accuracy of the analytical models.

Novel hybrid excited machine with flux barriers in rotor structure

PurposePermanent magnet (PM) electrical machines are becoming one of the most popular type of the machines used in electrical vehicle drive applications. The main drawback of permanent magnet machines, despite obvious advantages, is associated with the flux control capability, which is limited at high rotor speeds of the machine. This paper aims to present a new arrangement of permanent magnets and flux barriers in the rotor structure to improve the field weakening control of hybrid excited machines. The field weakening characteristics, back-emf waveforms and efficiency maps of this novel machine have been reported.Design/methodology/approachIn the study, finite element analysis was used to perform simulation research. Then, based on the simulation studies, an experimental model was built. The paper also presents selected experimental results.FindingsObtained results show that the proposed machine topology and novel control strategy can offer an effective flux control method allowing to extend the maximal rotational speed of the machine at constant power range.Practical implicationsThe proposed solution can be used in electric vehicles drive to extend its torque and speed range.Originality/valueThe paper presents original design and results of research on a new solution of a hybrid excited machine with magnetic barriers in a rotor.

Design of Integrated Magnetic Springs for Linear Oscillatory Actuators

Spring-assisted oscillating actuators allow the overall energy consumption of a system to be reduced. The concept relies on springs that store and release energy into the system when required. Conventional mechanical springs impose some limitations on a system, mainly in terms of compactness, friction, material fatigue, and failure. Magnetic springs have the potential to overcome these issues, especially for long-stroke high-frequency operation. We report here on the investigation of a magnetic spring into a linear oscillatory motor without any changes to the permanent magnet arrangement on the mover. We focus on a compact and highly integrated design with maximum energy storage capacity. Our analytic equations define the relevant geometrical parameters that exploit the potential of the system best and are on a par with a finite-element-based optimization. We also investigated the expected losses and demonstrate the importance of correct choice of materials to efficient operation. We validated our results using measurements from a prototype linear oscillatory motor featuring the proposed integrated magnetic spring.

V-I characteristics of a coreless ironless electric generator in a closed-circuit mode for low wind density power generation

This research deals with removal of ironcore lamination in electric generator to eliminate cog torque. A confinement technique is proposed to confine and focus magnetic flux by introducing opposing permanent magnets arrangement. The generator was fabricated and experimentally validated to qualify its loaded characteristics. The rotational torque and power output are measured and efficiency is then analyzed. At 100Ω load, the generator power output increased with the increased of rotational speed. Nearly 78% of efficiency was achieved when the generator was rotated at 250rpm. At this speed, the generator produced RMS voltage of 81VAC. Torque required to rotate the generator was found to be 3.2Nm. The slight increment of mechanical torque to spin the generator was due to the counter electromotive force (CEMF) existed in the copper windings. However, the torque required is still lower by nearly 30% than conventional AFPM generator. It is there concluded that this generator is suitable to be used for low wind density power generation application.

Performance and optimum characteristics by finite element analysis of a coreless ironless electric generator for low wind density power generation

Cogging is an attraction of magnetism between permanent magnets and soft ironcore lamination in a conventional electric ironcore generator. The presence of cog in the generator is seen somehow restricted the application of the generator in an application where low rotational torque is required. Cog torque requires an additional input power to overcome, hence became one of the power loss sources. With the increasing of power output, the cogging is also proportionally increased. This leads to the increasing of the supplied power of the driver motor to overcome the cog. Therefore, this research is embarked to study fundamentally about the possibility of removing ironcore lamination in an electric generator. This research deals with removal of ironcore lamination in electric generator to eliminate cog torque. A confinement technique is proposed to confine and focus magnetic flux by introducing opposing permanent magnets arrangement. There were several parameters analysed using the JMAG Designer. Transient response analysis was used in the JMAG Designer. The parameters analysed were the number of coil turns per phase, gap distance between the magnet pairs as well as the magnet grade used. These few parameters were analysed under the open circuit condition. Results showed with the increasing of gap distance, output voltage produced decreased. The increment of number of turns in the coils and higher magnet grades used, these increased the output voltage of the generator. With the help of these results, a reference point is established to get optimum design parameter for fabrication of working prototype.

Open circuit V-I characteristics of a coreless ironless electric generator for low density wind power generation

Cogging is an attraction of magnetism between permanent magnets and soft ironcore lamination in a conventional electric ironcore generator. The presence of cog in the generator is seen somehow restricted the application of the generator in an application where low rotational torque is required. Cog torque requires an additional input power to overcome, hence became one of the power loss sources. With the increasing of power output, the cogging is also proportionally increased. This leads to the increasing of the supplied power of the driver motor to overcome the cog. Therefore, this research is embarked to study fundamentally about the possibility of removing ironcore lamination in an electric generator. This research deals with removal of ironcore lamination in electric generator to eliminate cog torque. A confinement technique is proposed to confine and focus magnetic flux by introducing opposing permanent magnets arrangement. The concept is then fabricated and experimentally validated to qualify its no-load characteristics. The rotational torque and power output are measured and efficiency is then analyzed. Results indicated that the generator produced RMS voltage of 416VAC at rotational speed of 1762 RPM. Torque required to rotate the generator was at 2Nm for various rotational speed. The generator has shown 30% lesser rotational torque compared to the conventional ironcore type generator due to the absent of cogging torque in the system. Lesser rotational torque required to rotate has made this type of generator has a potential to be used for low wind density wind turbine application.

A direction-tunable shear horizontal mode array magnetostrictive patch transducer

Due to the simple wave structure and low-attenuation and non-dispersive properties, the lowest-order shear horizontal mode SH0 can realize the efficient large-scale damage detection in plate structures and shows a great application potential in non-destructive testing and structural health monitoring. In order to excite SH0 mode in aluminum plates, a direction-tunable shear-horizontal mode array magnetostrictive patch transducer (DT-SHMA-MPT) is developed based on the magnetostrictive effect. The proposed DT-SHMA-MPT consists of a transducer sleeve, four identical planar fan-shaped meander coils, four identical fan-shaped NdFeB permanent magnets, and a circular nickel patch. Four identical planar fan-shaped meander coils are connected in parallel to form a meander coil array. These planar fan-shaped meander coils are double-layer structures and made of flexible printed circuit (FPC). The experimental results show that the developed DT-SHMA-MPT can effectively excite and receive a single SH0 mode in aluminum plates. For the DT-SHMA-MPT with n planar fan-shaped meander coils and n fan-shaped permanent magnets (n = 4, 3, 2), its frequency response characteristics are tested at the center frequencies of 775 kHz, 780 kHz, and 783 kHz, which are close to the predicted value. Furthermore, the effects of the number of fan-shaped meander coils and corresponding permanent magnets on the directivity of the transducer are also investigated. The acoustic field distribution or the directivity of the transducer directly depends on the number of fan-shaped meander coils and permanent magnets. Finally, the direction tuning of proposed transducer is investigated. The ability of excitation and reception of this transducer can be controlled by tuning the directional arrangement of fan-shaped meander coils and permanent magnets.

An Improvement of Magnetic Flux Linkage in Electrical Generator using the novel Permanent Magnet Arrangement

An Improvement of Magnetic Flux Linkage in Electrical Generator using the novel Permanent Magnet Arrangement

Design and Analysis of a Flux Reversal Machine With Evenly Distributed Permanent Magnets

In this paper, a flux reversal machine (FRM), which has a larger torque density and a smoother torque waveform than the conventional FRM, is introduced. The FRM has the same combinations of stator and rotor slots, winding pole pair, and permanent magnet (PM) usage as the conventional FRM, but has different PM arrangements, i.e., in the conventional FRM, a pair of PMs is mounted on the surface of each stator teeth while the PMs of the FRM introduced in this paper are evenly distributed along the inner surface of the stator. First, the origination from the conventional FRM to the proposed FRM is introduced. Then, the effects of the rotor slot number, split ratio, stator/rotor slot opening ratio, PM thickness, and pole arc on the average torque and cogging torque are investigated and analyzed, which give a reasonable prediction for maximum achievable power density and minimum possible cogging torque of the proposed FRM. Moreover, the proposed FRM is compared with a conventional FRM in terms of back electromotive force, rated torque, pulsating torque, power factor, and overload capabilities. Finally, a 12-stator-slot/17-rotor-slot FRM prototype is built to verify the theoretical analyses.

An Experimental Study on the Effect of Thrust Force on Motor Performance in Linear Permanent Magnet Synchronous Motors

In this paper, the effect of thrust force on motor performance in Linear Permanent Magnet Synchronous Motor (LPMSM) was investigated. This study was carried out as experimental and motor control method was used in scalar control. The effect of thrust force with the vertical and horizontal placement of permanent magnets (PMs) in the fixed part, which is called the secondary side (the PMs were placed in this section), was evaluated according to test results. Test results that have been obtained from computer program were given in the last part. According to test results, the horizontal placement of PM has a positive and significant contribution to the thrust force. In this context, motor performance has affected in a positive way.

Optimal Structure Design of Permanent Magnet Motors Based on a General Pattern of Rotor Topologies

For the purpose of saving energy resources, it is extremely expected to develop highly efficient electric motors. Different types of permanent magnet (PM) arrangement can significantly affect the performance of the motors. Conventionally, the arrangement of the PMs is determined by designer’s experience. This paper focuses on the optimal design of PM arrangement in PM synchronous motors (PMSMs). We present a general pattern of the PM arrangement in PMSM. By varying the parameters of the general pattern, it can produce different types of PM arrangement in the rotor. The employed approach combines the global optimization method with the finite-element method for solving the optimization of the PM structures. Based on the proposed general pattern and optimization methods, the best PM arrangement in the motor can be automatically determined. In order to reduce computing loading, this paper employs the response surface models for reducing the computing time of objective functions. In the end, numerical tests are designed to showcase the effectiveness of the proposed method.

Optimal Design of Permanent Magnet Arrangement in Synchronous Motors

A general pattern, which can include different types of permanent magnet (PM) arrangement in PM synchronous motors (PMSMs) is presented. By varying the geometric parameters of the general pattern, the template can automatically produce different types of PM arrangement in the rotor. By choosing the best arrangement of PMs using optimization method, one can obtain a better performance and lower manufacturing cost. Six of the most widely used conventional types of rotor structures can be obtained through the parameter variation of the general pattern. These types include five embedded PM types and a traditional surface-mounted PM type. The proposed approach combines optimization method embedded with finite element method (FEM) for solving the multi-objective optimization for the PM structures. To save computing load, this paper employs a strategy of sub-group optimization, which is on account of the impact levels of the design parameters on the objective functions, and a parallel computation, which is a valid method to shorten the computing time. As an application example, a PMSM is optimally designed. Its simulation results and prototype experiments are provided to showcase the effectiveness of the proposed method.

Convective heat transfer in engine coolers influenced by electromagnetic fields

In engine coolers of off-highway vehicles, convective heat transfer at the coolant side limits both efficiency and performance density of the apparatus. Here, due to restrictions in construction and design, backwater areas and stagnation regions cannot be avoided. Those unwanted changes in flow characteristics are mainly triggered by flow deflections and sudden cross-sectional expansions. In application, mixtures of water and glysantine are used as appropriate coolants. Such coolants typically show an electrical conductivity of a few S/m. Coolant flow and convective heat transfer can then be controlled using Lorentz forces. These body forces are generated within the conducting fluid by the interactions of an electrical current density and a localized magnetic field, both of which are externally superimposed. In future application, this could be achieved by inserting electrodes in the cooler wall and a corresponding arrangement of permanent magnets. In this paper we perform numerical simulations of such magnetohydrodynamic flow in three model geometries that frequently appear in engine cooling applications: Carnot-Borda diffusor, 90° bend, and 180° bend. The simulations are carried out using the software package ANSYS Fluent. The present study demonstrates that, depending on the electromagnetic interaction parameter and the specific geometric arrangement of electrodes and magnetic field, Lorentz forces are suitable to break up eddy waters and separation zones and thus significantly increase convective heat transfer in these areas. Furthermore, the results show that hydraulic pressure losses can be reduced due to the pumping action of the Lorentz forces.