Magnet Machine Research Articles

Comparative Study of Consequent-Pole Switched-Flux Machines with Different U-Shaped PM Structures

This paper presents a comparative study of two consequent-pole switched-flux permanent magnet (CP-SFPM) machines with different U-shaped PM arrangements. In order to address the flux barrier effect in a sandwiched SFPM machine, two different alternate U-shaped PM designs are introduced to improve the torque capability, forming two CP-SFPM machine topologies. In order to reveal the influence of different magnet designs on the torque production, a simplified PM magneto-motive force (MMF)-permeance model is employed to identify the effective working harmonics in the two CP-SFPM machines. The torque contributions of the main working harmonics are subsequently quantified by a hybrid finite-element (FE)/analytical method. Multi-objective genetic algorithm (GA) optimization is then employed to optimize the design parameters of the proposed CP-SFPM machines. In addition, the electromagnetic characteristics of the CP-SFPM machines with two U-shaped PM arrangements are investigated and compared by the FE method. Finally, a 6/13-pole CP-SFPM machine with an optimally selected U-shaped PM structure is manufactured and tested to validate the FE analyses.

Comparative Study of Dual PM Vernier Machines

In this paper, two types of dual permanent magnet (PM) machines, i.e., stator slot dual-PM (SSDPM) machine and split-tooth dual-PM (STDPM) machine, are investigated and compared. Both machines have consequent pole structure with Halbach array PMs. Their difference lies in the position of stator PM. The SSDPM machine has Halbach array PMs in the stator slots, while the STDPM machine has PMs between the split teeth. Torque characteristics, i.e., average torques and torque ripples, of different slot/pole number combinations of the two machines are compared. The 24 stator slots/20 rotor slots/4 armature pole pair (24S20R4Pa) SSDPM machine with distributed windings and the 24 stator slots/10 rotor slots/4 armature pole pair (12S20R4Pa) STDPM machine with concentrated windings are compared under both open-circuit and on-load conditions. The results show that the SSDPM machine is more competitive by delivering higher torque density and higher power density.

Characteristic analysis of flux switching PM machine with various pole and slot combinations

This paper examines the influence of pole and slot combinations on the electromagnetic performance of the flux-switching permanent magnet (FSPMs) machine. For this purpose, first the production of air gap flux density in machine analytically discussed. Next, five different pole and slot combination are selected by using the knowledge of air-gap flux density expression. The performances of the different combinations are analyzed and compared using the finite element analysis (FEA), and optimal pole and slot combination is suggested. It is found that the pole and slot combination has a dominant effect on machine performance and needs to be considered during the design stage.

Magnetic Circuit Modeling of Dual-Armature Flux-Switching Permanent Magnet Machine

Three lumped-parameter magnetic circuit (LMC) models of dual-armature flux-switching permanent magnet (DA-FSPM) machines are proposed and compared in this article. First, the characteristics of the magnetic flux fields produced by the PM, stator armature reaction, and rotor armature reaction flux sources are analyzed, with particular attention paid to the air-gap and slot leakage flux paths. Based on the former analyses, three LMC models are developed, which consider the air-gap and slot leakage permeances in different ways. The electromagnetic performances of the DA-FSPM machines are predicted by the three LMC models and validated by the finite-element method, including the flux linkage, average torque, inductance, and power factor. The model accuracy sensitivity to the geometric parameters, copper loss allocation, electric loading, stator pole/rotor tooth number combinations, power level, and conductor distributions are analyzed. It shows that appropriate consideration of slot leakage permeance is important to improve the model accuracy.

Applicability of Magnetic Abrasive Machining by Means of Diamond Suspensions in Gas-Turbine Production

The use of magnetic abrasive machining in the production of components for gas-turbine airplane engines is considered. The abrasive machining of a titanium alloy, high-speed steel, and a hard WC–Co alloy by means of a suspension of diamond powder and carbonyl iron particles in a hydrocarbon liquid is analyzed.

Comparison of Neural Network NARMA-L2 Model Reference and Predictive Controllers for Nonlinear EMS Magnetic Levitation Train

Magnetic levitation system is operated primarily based at the principle of magnetic attraction and repulsion to levitate the passengers and the train. However, magnetic levitation trains are rather nonlinear and open loop unstable which makes it hard to govern. In this paper, investigation, design and control of a nonlinear Maglev train based on NARMA-L2, model reference and predictive controllers. The response of the Maglev train with the proposed controllers for the precise role of a Magnetic levitation machine have been as compared for a step input signal. The simulation consequences prove that the Maglev teach system with NARMA-L2 controller suggests the quality performance in adjusting the precise function of the system and the device improves the experience consolation and street managing criteria. Keywords: - Maglev train, NARMA-L2 controller, model reference controller, predictive controller DOI: 10.7176/IKM/10-4-03 Publication date: May 31 st 2020

Investigation of E-Core Modular Permanent Magnet Wind Turbine

Under the adverse trend of fossil energy attenuation and air pollution, wind power effectively alleviates the global energy crisis and environmental pollution. For wind turbines, especially large offshore wind turbines, their transportation, installation, and maintenance are very inconvenient. In order to solve this problem, this paper presents an E-core stator modular machine which inserts stator gap into the unwounded teeth of the fractional-slot concentrated winding (FSCW) permanent magnet (PM) machine. The winding factor of the new stator structure machine was derived. The electromagnetic models of 12-slot/10-pole and 12-slot/14-pole modular FSCW PM machines and traditional FSCW PM machines were established using the finite element analysis (FEA) software, and the open-circuit flux density, cogging torque, load torque, loss, and efficiency were simulated and analyzed. The results showed that the modular structure of E-core stator not only simplified the transportation, installation, and maintenance of wind turbines, but also optimized the electromagnetic performance of the 12-slot/14-pole machine, i.e., improved the output torque and operation efficiency.

Influence of Rotor-Pole Number on Electromagnetic Performance of Novel Double-Rotor Hybrid Excited Axial Switched-Flux Permanent-Magnet Machines for EV/HEV Applications

In this paper, a novel 6-stator-pole double-rotor hybrid excited axial switched-flux permanent magnet (DR-HEASFPM) machine is proposed for electrical vehicles. Based on 3-D finite element analysis, the influence of 10-, 11-, 13-, and 14-rotor-pole on the electromagnetic performance of DR-HEASFPM machine, including the magnetic field distribution, flux-linkage, back-EMF, flux regulation principles and capability, is comparatively investigated. The results show that the 6/10-, Ll-pole DR-HEASFPM machines exhibit higher PM flux-linkage and back-EMF. Moreover, the back-EMF of 6/11-pole machine is more sinusoidal and the flux-regulation capability is more excellent, which is suitable for wide speed-regulation application.

Exploring memory function in earthquake trauma survivors with resting-state fMRI and machine learning

BackgroundTraumatized earthquake survivors may develop poor memory function. Resting-state functional magnetic resonance imaging (rs-fMRI) and machine learning techniques may one day aid the clinical assessment of individual psychiatric patients. This study aims to use machine learning with Rs-fMRI from the perspectives of neurophysiology and neuroimaging to explore the association between it and the individual memory function of trauma survivors.MethodsRs-fMRI data was acquired for eighty-nine survivors (male (33%), average age (SD):45.18(6.31) years) of Wenchuan earthquakes in 2008 each of whom was screened by experienced psychiatrists based on the clinician-administered post-traumatic stress disorder (PTSD) scale (CAPS), and their memory function scores were determined by the Wechsler Memory Scale-IV (WMS-IV). We explored which memory function scores were significantly associated with CAPS scores. Using simple multiple kernel learning (MKL), Rs-fMRI was used to predict the memory function scores that were associated with CAPS scores. A support vector machine (SVM) was also used to make classifications in trauma survivors with or without PTSD.ResultsSpatial addition (SA), which is defined by spatial working memory function, was negatively correlated with the total CAPS score (r = − 0.22, P = 0.04). The use of simple MKL allowed quantitative association of SA scores with statistically significant accuracy (correlation = 0.28, P = 0.03; mean squared error = 8.36; P = 0.04). The left middle frontal gyrus and the left precuneus contributed the largest proportion to the simple MKL association frame. The SVM could not make a quantitative classification of diagnosis with statistically significant accuracy.LimitationsThe use of the cross-sectional study design after exposure to an earthquake and the leave-one-out cross-validation (LOOCV) increases the risk of overfitting.ConclusionSpontaneous brain activity of the left middle frontal gyrus and the left precuneus acquired by rs-fMRI may be a brain mechanism of visual working memory that is related to PTSD symptoms. Machine learning may be a useful tool in the identification of brain mechanisms of memory impairment in trauma survivors.

Experimental investigation and design optimisation for magnetic abrasive flow machining using response surface methodology

The finishing of surfaces of some of the aerospace parts and medical equipments was required to be of the finest quality. This work described the finishing of micro holes of aluminium cylindrical tubular type work specimens by one of the non-traditional machining method of finishing, i.e., magnetic abrasive flow machining. The abrasive media used for finishing contains newly prepared diamond based bonded magnetic abrasives. These abrasives were prepared by mechanical alloying followed by annealing method. The performance of magnetic abrasive flow machining process was evaluated in terms of surface roughness improvement rate. The process variables were optimised by employing response surface methodology. The parameters which showed prominent effect on surface roughness improvement rate were extrusion pressure, magnetic flux density and number of cycles. It was found through the experiments that the optimum result was obtained when extrusion pressure was 800 psi, magnetic field density was 0.6, and number of cycles was 25, which depicts that surface roughness improvement rate after finishing was 72.72% (Ra 0.22 μm). The results were also confirmed by analysing through scanning electron microscopy.

Preparation, microstructure analysis and performance evaluation of bonded magnetic abrasives

The traditional edged tool for machining is uneconomical for harder and difficult to machine materials. In view of the seriousness of this issue, the newly unconventional fine finishing process i.e., magnetic abrasive flow machining (MAFM) has been developed. However, the major constraint in wide spread adoption of this technology is the exorbitant cost of magnetic abrasives, which acts as a cutting tool in MAFM. In this paper, to improve the finishing performance, iron (Fe) powder mixed with diamond abrasives were prepared as bonded magnetic abrasives. These magnetic abrasives were prepared by mechanical alloying followed by annealing of diamond abrasives of 52 μm grit size and Fe powder of 49 μm grit size. These abrasives were micro-structurally analysed. The results indicate that densification increases and porosity decreases with increasing temperature. Further it was clarified that the prepared bonded magnetic abrasives has potential performance as the new magnetic abrasives for fine finishing.

A Nonlinear $q$-Axis Inductance Modeling of a 12-Slot 10-Pole IPM Using Approximate Analytical Methods

This article introduces a novel nonlinear model for the $q$ -axis inductance of a Fractional Slot Concentrated Winding Interior Permanent Magnet (FSCW-IPM) machine in order to decrease the time needed to obtain a solution. The complicated geometry and nonlinear magnetic behavior of the core make analytical modeling difficult. So numerical methods are usually used to model machines in which magnetic saturation plays an important role. The winding function of a 12-slot 10-pole FSCW-IPM machine is analyzed and a magnetic equivalent circuit is obtained using the Lumped Parameter Method (LPM) according to the MMF distribution analysis. A mathematical function which represents the magnetic behavior of the core material is appropritely selected to reduce the equations, which show the relationship between the flux and MMF of every lumped parameter into the one equivalent equation. After that, perturbation theory and Pade approximants are used to solve the nonlinear equivalent equation. Finally, a new nonlinear analytical model and solution method is introduced for 12-slots 10-pole FSCW-IPM and the simulation time is decreased to under 0.5 s while it takes about 10 mins with FEA because the proposed method does not need any iteration. The proposed method is compared with FEA and experimental results and the comparison shows the proposed method has sufficient accuracy.

Influence of Axial Pressure on Parameters of Single Pancake HTS Coil

The single pancake HTS coil (inner diameter (ID) 85 mm, outer diameter (OD) 96.5 mm, 35 turns) was investigated under axial pressure up to 12 tons in liquid nitrogen to test the influence of axial pressure on critical properties in a central plane of designed HTS double pancake–based 3 T solenoid magnet for magnetic refrigeration machine. It was shown that 15-μm thick Al2O3 oxidized coating of the aluminum disk (which was used as a heat-conducting structure) is stable (in terms of breakdown voltage and mechanical strength) with such a loading. Critical current of pancake coil does not change with axial compression up to 30 MPa pressure and starts to decrease irreversibly if P > 30 MPa. Designed axial pressure level in 3 T magnet does not exceed this permissible boundary.

Research Progress and New Patents of Magnetic Grinding Machine

Background: Mechanical parts in processing and manufacturing process will produce burr, scratches and other surface quality problems, which have adverse effects on the precision, use, reprocessing location, operation safety and appearance quality of the parts, so it is necessary to grind the workpiece surface. Objective: Based on the recent development in the field of magnetic grinding and related patent research, it can provide reliable help to solve the problem of finishing the surface of parts with complex shapes and small volumes. Methods: This paper reviewed some patents and research advances related to magnetic abrasive finishing, and the advantages and disadvantages of the magnetic grinding machine in the finishing process were summarized. The outstanding grinding effect of the new vibration assisted magnetic grinder was introduced. Results: The working characteristics of various magnetic grinding machines were summarized, and the development trend of magnetic grinding and finishing was prospected. Conclusion: Magnetic abrasive finishing has good flexibility, strong self-sharpening, wide applicable scope, high processing efficiency, simple processing equipment and low cost. It can control the grinding efficiency and grinding precision. The machining efficiency and quality of magnetic grinding can be improved with the appropriate amplitude of vibration assist, and the surface quality can be improved significantly.

Modified switching scheme‐based explicit torque control of brush‐less direct current motor drive

A modified explicit torque control (ETC) scheme for permanent magnet (PM) machine with non-sinusoidal back emf is investigated in this article. The conventional ETC scheme for the PM machines with non-sinusoidal back emf furnishes a wide band for the switching frequency and offers a faster response in the torque. In this article, a modified scheme for switching vector selection is proposed to reduce the switching frequency while maintaining the advantage of faster torque response. Other than the conventional two-phase excitation, which uses opposite vectors for switching to get the speedier response in torque, the modifications proposed for the ETC of PM machine are (i) a closer vector selection from the available two-phase vector plane and (ii) a combination of two phase and three phase excitation. Both these modifications gives a faster response in the torque as that of conventional ETC, while this offers a reduction in the switching frequency. Switching frequency variations are expressed mathematically, and experimental results are presented for the modified schemes of ETC and for the conventional ETC based to validate the proposed scheme.

Magnetic Abrasive Flow Machine Based Super Surface Finishing

Magnetic Abrasive Flow Machine Based Super Surface Finishing

Design route towards a PM machine for rotorcraft environments

This paper discusses the design route followed in the development of a permanent magnet (PM) machine for electrical power generation on board a rotorcraft (helicopter). The focus of the machine design is to optimise system power density, efficiency, and robustness – all of which are crucial considerations in aerospace applications. A matrix of designs was created consisting of two stators with different winding conductors – copper and aluminium – and three rotors, each using different containment sleeve materials. These include two semi-permeable metallic sleeves, which act to decrease the effective air gap. Combinations of the different materials will yield different system-level power densities and efficiencies. Here, all the designs are presented along with the initial test results for the baseline machine combination validating the design predictions.

Separation and comparison of average torque in five‐phase IPM machines with distributed and fractional slot concentrated windings

This study proposes a method to separate average permanent magnet (PM) torque and average reluctance torque of five-phase interior permanent magnet (IPM) machine based on transient finite element method (FEM). The key of this method is to count total torque as four torque components by considering the saturation and cross-magnetisation between d – q axes, and every torque components are calculated from d–q axes parameters directly. The parameters in d–q axes reference frame are transformed from ABCDE reference frame via five-phase Park transformation. Comparing with the existing methods, the proposed method maintains the same accuracy while time saving because d–q axes parameters can be obtained directly by one-time FEM simulation. Meanwhile, the proposed method is adopted to separate the PM torque and reluctance torque from two five-phase IPM machines with fractional-slot concentrated winding (FSCW) and integral-slot distributed winding (ISDW). Finally, the FEM and experimental results show that the IPM machine with FSCW produces lower reluctance torque ratio than that of IPM machine with ISDW. Besides, the results demonstrate that the flux-weakening performance connects with characteristic current (Ψ PM d / Ldd ) strongly.

Analysis of a Novel Consequent-Pole Flux Switching Permanent Magnet Machine With Flux Bridges in Stator Core

In this paper, a novel flux switching permanent- magnet machine (FSPM) with consequent-pole magnets and flux bridges in the stator core is proposed to improve the torque capability of FSPMs with high pole ratios. The stator yoke and flux bridges adjacent to the magnets can provide magnetic paths for the main working harmonic field, thus the magnetic reluctance of the working harmonic field is reduced, and the flux modulation effect, winding back-electromotive force (EMF), and output torque of the proposed FSPM can be significantly improved compared to the regular FSPM with high pole ratios. The operation principles and stator–slot/rotor–slot combinations of the proposed FSPM are introduced. Then, the influences of pole ratio, split ratio, slot opening ratio, and PM width on the torque density of the proposed FSPM is investigated using finite element analysis. Moreover, after the investigations, a proposed FSPM is compared to a regular FSPM in terms of back-EMF, rated torque, power factor, etc. Finally, to verify the theoretical analysis, a 12-stator–slot/14-rotor–slot FSPM is built and tested.

Preliminary studies of 12S-8P and 12S-14P Hybrid-Excited Flux Switching Machine with FEC in radial direction by using JMAG-designer software

In this paper, design analysis of Hybrid- Excited Flux Switching Machine (H-EFSM) with 12Slot-8Pole (12S-8P) and 12Slot-14Pole (12S-14P) topologies are presented. H-EFSM has been introduced in which the advantage of Permanent Magnet (PM) machines and DC Field Excitation Coil (FEC) synchronous machines is combined. H-EFSM design proposed less permanent magnet consumption, high to torque/power density and high efficiency. In recent, most of H-EFSM having FEC arranged in theta direction that affect in flux production which cause less flux generation and machines performances. Therefore, a design of 12S-8P and 12S-14P H-EFSM with FEC arranged in radial direction is proposed to prevent flux cancellation and produce high flux linkage. Performance analysis of 12S-8P and 12S-14 H-EFSM such as PM flux, induced voltage, cogging torque and flux distribution are investigated by 2-D Finite Element Analysis (2D-FEA). A design with 12S-14P configuration has achieved the higher torque and power with 220.15Nm and 92.45kW, respectively at maximum field and armature current density