Magnetic Path Research Articles

Analysis of Claw Pole Transverse Flux Inductor Motor by Means of Magnetic Equivalent Circuit.(Dept.E)

In a preliminary design stage of claw pole fransverse flux inductor motor with E-core, an accurate magnetic calculations are very complicated due to the field arrangement. A special heavy burden is the estimation of leakage flux in the non-useful paths. Extra iron will be needed to carry this flux if saturation is to be avoided in the useful paths. This paper presents a simple equivalent circuit method by which the performance of various magnetic paths are estimated analytically. The method is based on the assumption that the flux paths are made up of straight and circular segments. It can be simply and quickly applied to examine the effects of varying the major dimensions of the motor. Experimental measurements are carried out on a simple static model to verify the proposed method. The comparison between the analytical results obtained from an ideal motor and the experimental results shows that they are in better agreement.

Design, modeling and optimization of an N-shape electromagnetic energy harvester for smart bearing of high speed train

Smart bearings have integrated sensors and processor and could monitor the real time status of the mechanical equipment. To achieve a long-term service of the smart bearing without human maintenance, the self-powering capability is of great necessity. This paper proposes an N-shape electromagnetic energy harvester (NEMEH) with cylindrical Halbach array embedded within an axle box bearing for the high speed train. The proposed electromagnetic energy harvester is radially embedded in the smart bearing, which includes arc-shaped magnets, an N-shape electric steel and coils. The arc-shaped Halbach array and the N-shape electric steel form a concentrated and closed magnetic flux path, which could improve the magnetic performance of the harvester. A magnetoelectric coupling model of the proposed harvester is derived and shows good agreement with the finite element analysis. An optimization route is performed to maximize the output power under the dimension constraint of the smart bearing. Experimental results demonstrate that the proposed theoretical model can well estimate the output of the harvester. The power generation of a prototype with optimal structure parameters could reach 4.26 W at a 1200 r min−1 rotational speed and a 2 mm air gap. It demonstrates that the developed NEMEH is capable of harvesting rotational motion energy to power the wireless sensor nodes.

Magnetic field line random walk and solar energetic particle path lengths

Context. In 2020 May-June, six solar energetic ion events were observed by the Parker Solar Probe/IS⊙IS instrument suite at ≈0.35 AU from the Sun. From standard velocity-dispersion analysis, the apparent ion path length is ≈0.625 AU at the onset of each event. Aims. We develop a formalism for estimating the path length of random-walking magnetic field lines to explain why the apparent ion path length at an event onset greatly exceeds the radial distance from the Sun for these events. Methods. We developed analytical estimates of the average increase in path length of random-walking magnetic field lines, relative to the unperturbed mean field. Monte Carlo simulations of field line and particle trajectories in a model of solar wind turbulence were used to validate the formalism and study the path lengths of particle guiding-center and full-orbital trajectories. The formalism was implemented in a global solar wind model, and the results are compared with ion path lengths inferred from IS⊙IS observations. Results. Both a simple estimate and a rigorous theoretical formulation are obtained for field-lines’ path length increase as a function of path length along the large-scale field. From simulated field line and particle trajectories, we find that particle guiding centers can have path lengths somewhat shorter than the average field line path length, while particle orbits can have substantially longer path lengths due to their gyromotion with a nonzero effective pitch angle. Conclusions. The long apparent path length during these solar energetic ion events can be explained by (1) a magnetic field line path length increase due to the field line random walk and (2) particle transport about the guiding center with a nonzero effective pitch angle due to pitch angle scattering. Our formalism for computing the magnetic field line path length, accounting for turbulent fluctuations, may be useful for application to solar particle transport in general.

3-D Equivalent Magnetic Network Modeling and FEA Verification of a Novel Axial-Flux Hybrid-Excitation In-wheel Motor

In order to solve the problems of poor capacity and unsatisfactory efficiency of flux-weakening control for the axial-flux permanent magnet (AFPM) machines with surface-mounted permanent magnet (PM) rotor structure, a new axial-flux hybrid-excitation machine (AFHEM) with double consequent-pole rotors is proposed, which combines the high torque density of the AFPM machine and the flexible flux regulation of the hybrid excitation machine. It meets the stringent requirements of the distributed in-wheel motor electric drive vehicle for high efficiency and high torque density. The topology, principle, and basic electromagnetic properties of the new axial-flux hybrid-excitation in-wheel motor are presented in this article. Based on the complex magnetic circuit of the AFHEM, a 3-D equivalent magnetic network (EMN) model is established. The air-gap flux density, flux linkage, back EMF, torque, and fault tolerance ability of the motor are solved through the EMN model and compared with the 3-D finite element analysis (FEA) to verify its validity and correctness. It is hoped to form a rapid design method for the new type of motor with the complex structure of 3-D magnetic flux path property. Finally, based on the EMN model, the influences of the magnetic saturation on the excitation regulation capability of the proposed AFHEM are analyzed, which provides a guideline for the optimization design of the new AFHE in-wheel motor.

Infrared phonon spectroscopy on the Cairo pentagonal antiferromagnet Bi2Fe4O9 : A study through the pressure-induced structural transition

Magnetic and crystallographic transitions in the Cairo pentagonal magnet ${\mathrm{Bi}}_{2}{\mathrm{Fe}}_{4}{\mathrm{O}}_{9}$ are investigated by means of infrared synchrotron-based spectroscopy as a function of temperature (20--300 K) and pressure (0--15.5 GPa). One of the phonon modes is shown to exhibit an anomalous softening as a function of temperature in the antiferromagnetic phase below 240 K, highlighting spin-lattice coupling. Moreover, under applied pressure at 40 K, an even larger softening is observed through the pressure-induced structural transition. Lattice dynamical calculations reveal that this mode is indeed very peculiar as it involves a minimal bending of the strongest superexchange path in the pentagonal planes, as well as a decrease in the distances between second-neighbor irons. The latter confirms the hypothesis made by Friedrich et al., [J. Phys.: Condens. Matter 24, 145401 (2012)] about an increase in the oxygen coordination of irons being at the origin of the pressure-induced structural transition. As a consequence, one expects a new magnetic superexchange path that may alter the magnetic structure under pressure.

Improving the Force and Time Response of a DC Solenoid Electromagnetic Actuator by Changing the Lower Core Angle

The aim of almost any electromagnetic actuator development is to increase the electromagnetic force with which an actuator acts on a plunger with as fast a time response as possible while maintaining the dimensions as small as possible. This paper presents research on the impact of the lower core angle on the force and time response of a DC solenoid electromagnetic actuator. The research method is based on the analytical analysis of the magnetic path of the DC solenoid electromagnetic actuator and a comparison with the numerical simulation results. A transient numerical simulation was performed on a 2D axial-symmetric model of the electromagnetic actuator and included simultaneously solving time-dependent partial differential equations of the electromagnetic actuator’s magnetic, electrical, and mechanical subsystems. The magnetic subsystem was analyzed by the finite element method (FEM) using the ANSYS Electronics software package. The three prototype models with different lower core angles were produced and tested in the accredited Laboratory Center of KONČAR Electrical Engineering Institute. The obtained measurements are compared with the analytical results and numerical simulation results.

Optimization Analysis of Automotive Asymmetric Magnetic Pole Permanent Magnet Motor by Taguchi Method

In order to improve the air-gap flux density of the permanent magnet synchronous motor and reduce the cogging torque, a novel structure with asymmetric magnetic poles for automobile was proposed. Based on the characteristics of the parallel magnetic circuit, the magnetic flux path diagram is established. And the equivalent magnetic circuit model is established by the equivalent magnetic circuit method. The Taguchi method is used to be a multiobjective optimization algorithm. The total harmonic distortion of the air-gap flux density is the first optimization goal. The second and third optimization goals are the cogging torque and the average of output torque, respectively. And the torque ripple is a constraint condition. The optimized parameter combination is obtained by the Taguchi method. Finite element simulation analysis and prototype test are carried out for the optimized motor structure. The results show that the total harmonic distortion of air-gap flux density is reduced by 36.7% comparing with the initial structure. The cogging torque is reduced by 26.0%. And the average output torque is increased by 4.8%.

Investigation and Comparative Study of 12/16 C-core and Conventional Radial Flux Switched Reluctance Motor under Coil Fault Conditions . (Dept. E)

Owing to the large quantity of conventional passenger vehicles with internal combustion engines, energy shortages and environmental pollution are now Seen as important problems. Electric vehicles (EVs) have the best energy savings and zero emission vehicles option. Radial Flux Switched Reluctance Motor (RFSRM), and Axial Flux Switched Reluctance Motor (AFSRM) have shown promise in wheel motor design of electric vehicles. While C-core is modelled, giving advantages of both radial and axial flux SRM. Based on a three-phase 12/16 pole structure, C-core RFSRM and conventional RFSRM are investigated and compared under different types of coils failures, while their impact on the average torque for both motors is presented. Comparisons of average torques at different coils` fault conditions between C-Core RFSRM, and conventional RFSRM have been done by finite element analysis (FEM). The segmental structure of C-Core RFSRM and its independent separate magnetic path for its coils, give it the superiority more than conventional RFSRM for in-wheel electric vehicle application.

Structurally-layered soft magnetic Fe-Si components with surface insulation prepared by shell-shaping selective laser melting

Recently, selective laser melting (SLM) of soft magnetic components (SMCs) has attracted great interest due to its high accuracy in three-dimensional shaping of hard-to-form high performance alloys (e.g. Fe-6.5 wt%Si), which are being highly pursued for the realization of small and lightweight next-generation electric motors. However, SLMed SMCs with internal insulation have never been successfully demonstrated because there are no suitable insulation materials to withstand extremely-high-temperature laser processing. Here we introduce a novel shell-shaping selective laser melting (SS-SLM) process and demonstrate highly-dense (relative density > 98%) structurally-layered Fe-6.5 wt% SMCs with surface insulation. In particular, high-temperature heat treatment induced grain growth and dramatically enhanced magnetic properties, including coercivity of 34.6 A/m, permeability of 7393, and saturation magnetization of 1.68 T. Furthermore, a sol-gel-based process yielded a uniform and dense SiO2 insulation layer on the shell surface, which effectively confines eddy current only in the shell. Remarkably, core loss of 52.5 W/kg (at 1 kHz, Bm = 1 T) was observed with definable minimum sheet thickness of 0.2 mm. Finally, we demonstrate structurally-layered SMCs (stators for novel axial-flux motors) with surface insulation, which eventually can be used to realize a three-dimensionally optimized magnetic path and considerably increased power density with high efficiency.

Conceptual design of magnetic force control system using wedge mechanism

This paper presents a conceptual design and proof-of-concept to control magnetic force using a wedge mechanism. The concept starts with the general knowledge that magnetic force is inversely proportional to distance. A magnetic model is generated consisting of a permanent magnet (PM), two magnetic flux paths, two wheels, and a steel plate. This model is subjected to formulate a mathematical relationship between the movement of the PM and a magnetic force exerted onto the steel plate. A 3D simulation has been conducted to verify the effectiveness of the developed mathematical model. The comparison between the mathematical and simulation models is likely to be fair. The next is to design a wedge mechanism which is composed of two wedges, a trenching plate, and a stepping motor. Finally, the proof-of-concept is placed on a magnetic force measurement and subjected to experiments. The result shows that the changes in the magnetic force according to the PM movements are 84.5% with simulation and 80.1% with the experiments, respectively. It can be concluded that the proposed concept is effective in reasonably controlling the magnetic force.

Optimal rotor poles and structure for design of consequent pole permanent magnet flux switching machine

Permanent magnet flux switching machines (PMFSM) have attracted significant research interest and are considered as competent candidates when higher torque density is primary requirement. However, conventional PMFSMs uses excessive rare earth PM volumes which ultimately increases machine the machine weight and PM cost. Moreover, the PMs extended at the stator yoke results in stator leakage flux which degrades the performance. To suppress the leakage flux and diminish the PM volume, the consequent pole PMFSM (CPPMFSM) with flux bridges and barriers encompassing partitioned circumferential and radial magnetized PMs is proposed, thereby ensuring an alternate magnetic path for the working harmonics which improves the modulation effect and flux distribution. Moreover, the influence of the rotor pole number on seven different rotor structures namely, curved rotor, trapezoidal rotor, wide rotor tooth tip, wide rotor base width, rectangular segmented and eccentric rotors are investigated based on the electromagnetic performance and stress distribution. Finite element analysis (FEA) reveals that the 12S-13P CPPMFSM with a wider rotor base offers comparatively better electromagnetic performance. Compare to the conventional PMFSM, the proposed CPPMFSM reduces the PM volume which minimizes the overall machine cost and weight, suppresses the torque ripples by 16.49%, diminishes total harmonic distortion (THD) by 35.24% and decreases cogging torque by 32.88%. Furthermore, the torque and power density are enhanced by 7.028% and 7.025% respectively.

Nonlinear Modeling of a C-Core Connected Two-Phase Switched Reluctance Motor

The main idea of this paper is to offer a continuous C-cores unique configuration for switched reluctance motor (SRM) and to present an analytical model for its analysis. The advantages of this structure are having a short path for the main part of the magnetic flux, resulting in less core losses and as well as less negative torque. On the other hand, there is less leakage flux in the proposed structure. Another advantage of this structure is that it has a high mean torque compared to conventional structures, so that this increase in mean torque also increases a small amount of torque ripple, which is negligible. However, power density at a constant volume increases relatively much. The proposed SRM is analyzed by the finite element method (FEM) and by employing a magnetic flux density pattern and magnetic fluxes path, its magnetic equivalent circuit (MEC) is obtained. In this MEC model, the main fluxes and leakage fluxes are fully modeled. After its complete analysis, electromagnetics torque, inductance, flux-linkage, mean torque, and peak torque are evaluated. Static and dynamic performances are then determined. Finally, the proposed SRM was prototyped and tested. The experimental results consisting of static torque, flux-linkage, voltage, and current waveforms and input power are compared with the corresponding results in the MEC model and FEM. The comparisons verify the accuracy and validity of the introduced analytical model. Besides, static torque, flux-linkage characteristics, and dynamic performance at a nominal speed of 1000 rpm and the current chopping control mode with chopping 5A under the load of the proposed SRM are compared with the conventional SRM and its merits are observed.

Detailed analytical modeling for electromagnetic performance in actively shielded superconducting machines

This study presents detailed analytical modeling for electromagnetic performance analysis of actively shielded superconducting machines with air-cored slotless armatures. An actively shielded superconducting machine is composed of a type of nonmagnetic material to prevent saturation of the magnetic flux path, as the field coil has a high magnetic field, and a shield coil is installed on the outside for magnetic shielding. This study presents an analytical modeling technique that considers not only the distribution of armature coils with distributed windings but also the shapes of the field and shield coils. Analytical solutions for each domain are derived using electromagnetic theory, partial differential equations, and boundary conditions. Based on the analytical solutions, electromagnetic performances are analyzed. The analysis results obtained from the proposed analytical method are verified by comparing them with those of finite element analysis.

Thermal capability of electric vehicle PMSM with different slot areas via thermal network analysis

In this paper, the effect that a varied stator slot size has on the efficiency and thermal capability of a permanent magnet synchronous machine for an electric vehicle, is evaluated and quantified. A machine with four differently sized slot areas was electromagnetically evaluated with finite element analysis, and thermally with a lumped parameter network model. By decreasing the slot size while keeping other dimensions fixed, the core losses reduce due to the wider magnetic path, whereas the winding losses increase. Additionally, a higher maximum torque is reached due to reduced saturation. Results are compared in the machine’s torque-speed operating area regarding machine-part and total losses, continuous torque and transient overload capability, as well as during 19 low, middle and high-speed drive cycles regarding energy losses and peak winding temperature. The largest slot showed the lowest winding losses and thus the highest thermally limited torque capability. In contrast, the energy losses with the largest slot were the highest in 13 of the drive cycles, and the lowest in 11 of them with the smallest slot due to its lower part load (i.e. core) losses. The smallest slot would also result in the lowest material cost since it has the least copper. • Larger PMSM stator slot gives higher continuous torque than a smaller with same rotor and current. • Smaller PMSM stator slot gives higher peak torque than a larger with same rotor and peak current. • Smaller PMSM stator slot gives lower total losses than a larger during many official drive cycles.

Effectiveness of Magnetic Composite Material on Copper Loss Reductions and Misalignment in Copper‐Plate‐Coils for Wireless Power Transmission

Wireless power transmission systems are suitable for use in charging systems for plug‐in hybrid vehicles and electric vehicles, particularly when considering safety and convenience. Wireless power transmission coils are made of litz copper wire to reduce copper losses at high frequencies. However, litz wires are expensive owing to their complicated structure and large number of manufacturing steps. Herein, a copper‐plate‐coil is proposed that can be manufactured at a low cost is proposed. A magnetic flux path control technique is also proposed to reduce copper losses. The use of a magnetic composite material for realizing magnetic flux path control technology reduces the alternative current resistance by 50%. In addition, this study reports the effects of the magnetic composite material on coupling coefficients observed during coil misalignment. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Improved Inductance Calculation in Variable Power Inductors by Adjustment of the Reluctance Model Through Magnetic Path Analysis

This article presents a study to improve the inductance calculation of magnetic components in power converters, of particular interest, in the case of applications using variable inductors. In order to increase the accuracy of the estimation of the reluctance paths, several factors have been taken into consideration, such as the permeability definition under saturation, the temperature effect on the magnetic material behavior, and the distribution of saturated regions in the magnetic core. The methodology of the present study is to compare the analytical models derived from circuital equivalents against finite-element analysis numerical techniques, in order to validate the proposed model of a variable inductor, including the effects of the mentioned factors. The proposed model is then compared with experimental measurements to prove its validity. Finally, a design example for the variable inductor is presented.

2-D Analysis Method for Synchronous Reluctance Motors Considering End-Plate Effect

This paper presents a 2-D analysis of synchronous reluctance motors (SynRMs) considering the end-plate effect. In an electric machine with a laminated steel core, an end-plate is often attached to the rotor core to support the structural robustness of the machine. End-plates occasionally comprise carbon-steel, which changes the magnetic behavior of the electric machine. Thus, an electric machine that utilizes the 3-D finite element analysis (FEA) should be designed to consider the comprehensive magnetic flux path. However, the application of 3-D FEA for the whole design process is computationally expensive. Therefore, we proposed a 2-D FEA-based design strategy that can consider the additional magnetic path of the end-plate for SynRMs. The proposed analysis method was developed based on the magnetic equivalent circuit analysis and $d$ - and $q$ -axis flux linkage calculation. The effectiveness of the proposed method was verified by presenting the actual design case of a SynRM and via an experimental study.

A Gd-based borate-carbonate framework exhibiting a large magnetocaloric effect at a low magnetic field.

A 3D borate-carbonate framework, GdB(OH)4CO3 (1), was synthesized. Magnetic study reveals that its MCE is up to 33.5 J kg-1 K-1 at 2 K and 2 T, due to the introduction of a long magnetic exchange path of Gd-O-B-O-Gd leading to 1 exhibiting weak magnetic interaction.

Design and Analysis of a Novel Gravity-Compensating Vertical Linear Motor

We propose a vertical linear motor (VLM) for semiconductor manufacturing equipment that compensates for the weight of the moving part by using the balance of magnetic and elastic forces. The developed VLM achieves zero stiffness with a constant upward force over a working range. The magnetic circuit of the VLM is designed to provide a linear negative stiffness over a ±2 mm stroke, with an upward force of 14 N at a 0 mm stroke. The negative stiffness is compensated for by the positive stiffness of elastic component-like springs. The upward force is then constant over the working range and corresponds to the weight of the moving part. The proposed VLM is designed to minimize the coupling effects of stiffness and gravity compensation forces by using magnetic flux saturation and magnetic flux path design. We investigate the effects of each design parameter on VLM operation through finite element analysis. Finally, the simulated forces in the proposed VLM are experimentally verified, indicating a linear negative stiffness of approximately −13.5 N/mm and a gravity compensation force of 14.9 N.

Significant enhancement of magnetic shielding effect by using the composite metamaterial composed of mu-near-zero media and ferrite

The magnetic shield plays an important role in magnetic near-field control. However, the requirements of efficiency, ultra thinness, lightness and cheapness are still the challenges. Here, we firstly propose a composite metamaterial in which the mu-near-zero media is covered with a ferrite slab. We verify that this structure can enhance the shielding effectiveness (SE) in a small area. Furthermore, we optimize the magnetic path by changing the bulk ferrite slab into a patterned slab. In this way, significant SE enhancement can be achieved in a large area. Experimental results show that the maximum SE of the composite metamaterial with a patterned ferrite is 20.56 dB, which is nearly 19 dB higher than that of a single ferrite slab with the same thickness of the composite metamaterial. The results on the composite metamaterial would be very useful in the applications involving magnetic shielding.