Showing papers on "Magnetic circuit published in 2018"
TL;DR: A simple and practical magnetic equivalent circuit (MEC) based analytical technique for calculating the performance parameters of the permanent magnet (PM) eddy current coupling is presented and shows that in a considerably wide range of slip speeds, the torques predicted by the presented method match well with those obtained by both the three-dimensional finite element analysis and experimental measurement.
Abstract: A simple and practical magnetic equivalent circuit (MEC) based analytical technique for calculating the performance parameters of the permanent magnet (PM) eddy current coupling is presented. In the proposed MEC model built with the lumped parameters, the eddy current effects are inherently taken into account by introducing a branch magnetic circuit allowing for the magnetomotive force and the reaction magnetic flux. A complete formulation for the reaction flux which is treated as a kind of leakage flux is derived. A verification process is conducted and it is shown that in a considerably wide range of slip speeds, the torques predicted by the presented method match well with those obtained by both the three-dimensional finite element analysis and experimental measurement. The new MEC-based method also proves to be effective in the performance simulation of the PM eddy current coupling with different design parameters. In addition, the limitation of the proposed approach is also discussed and the reasons are fully investigated.
76 citations
TL;DR: In this paper, a novel spoke array PMV machine is proposed to improve working flux density and the torque density of PMV machines, where alternate magnetic bridges are added in the rotor core to connect iron pieces with same polarity and provide magnetic circuit for the low-pole number working magnetic field.
Abstract: In recent years, permanent magnet vernier (PMV) machines are attracting more and more attentions owing to their high torque density feature, which is mainly benefited from its special operation principle called flux modulation effect. Nevertheless, It is found that its working flux density is low, viz., ∼0.3T for modulated flux density in the surface mounted PMV machines. Hence, there is a really large space to further improve the torque density of PMV machine. The spoke array magnet is widely used in the regular PM machine to improve working flux density. However, the flux barrier effect of spoke array magnet for the PMV machine has been proved, and a large torque reduction would be introduced in the high pole ratio spoke array PMV machine. In this paper, a novel spoke array PMV machine is proposed to improve working flux density and the torque density of PMV machines. The alternate magnetic bridges are added in the rotor core to connect iron pieces with same polarity and provide magnetic circuit for the low-pole number working magnetic field, hence the no-load back EMF and output torque of the proposed machine can be significantly improved. Moreover, analytical airgap flux density distribution based on equivalent magnetic circuit is presented to reveal the mechanism of working flux density improvement, and finite element analysis is used to investigate the performance features and structure parameter influence on the key performances, viz., back EMF and torque, of the proposed machine. Finally, a 25 N·m prototype has been built and tested to validate these analyses.
68 citations
TL;DR: The aim of this paper is to establish an accurate, yet computationally fast, model suitable for optimal design of AFVR resolvers based on magnetic equivalent circuit (MEC) and conformal mapping, which are in turn based on Schwarz–Christoffel mapping.
Abstract: Axial flux variable reluctance (AFVR) resolvers have substantial benefits that make them suitable for motion control drives. However, they suffer from insufficient accuracy, especially in high-accuracy applications. Hence, optimizing the AFVR resolver structure is necessary for improving its commercial usage. However, its accurate modelling needs three-dimensional (3-D) time stepping finite element analysis (TSFEA) that is computationally expensive and unsuitable for co-usage with optimization algorithms. The aim of this paper is to establish an accurate, yet computationally fast, model suitable for optimal design of AFVR resolvers. The working of the proposed model is based on magnetic equivalent circuit (MEC) and conformal mapping, which are in turn based on Schwarz–Christoffel mapping. The model uses conformal mapping to calculate reluctances that are used in MEC for calculating magnetic fluxes linkages, inductances, and induced voltages. Then, the induced voltages are used for calculating angular position. The results of the proposed model are compared with those of 3-D TSFEA. Finally, the experimental prototype is used to evaluate the developed analytical model.
67 citations
TL;DR: In this paper, the authors evaluate the effective coupling factor and leakage magnetic field of a 20-kW inductive power transfer (IPT) system that uses a combination of tripolar pad and circular pad (CP) topologies over a range of lateral displacements.
Abstract: Recently, a magnetic pad called the tripolar pad (TPP) has been introduced for inductive power transfer (IPT) systems. This paper evaluates the effective coupling factor and leakage magnetic field of a 20-kW IPT system that uses a combination of TPP and circular pad (CP) topologies over a range of lateral displacements. The results show that the effective coupling factor and the leakage magnetic field of the TPP–TPP system are substantially better when the secondary is displaced away from ideal alignment. Leakage magnetic field is reduced up to 43% compared to the CP–CP system at the worst-case misalignment, which is due to the ability of the TPP–TPP system to generate and capture different types of magnetic field shapes. Simulation methods for both the TPP and CP are validated in the laboratory using a 2-kW system operating at 85 kHz.
63 citations
18 Jun 2018
TL;DR: In this paper, the demagnetization equivalent magnetic circuit (EMC) model of the investigated LRE-IPMSM is established and the effects of structure parameters on the PM flux density are investigated.
Abstract: Rare-earth permanent magnet synchronous machines (RE-PMSMs) are widely used in electric vehicles (EVs) due to their characteristics of high efficiency, high torque density and high power factor. While the dramatic price fluctuations of the rare-earth permanent magnets (PMs) have been restricted the application of RE-PMSMs. Hence, the less-rareearth interior permanent magnet synchronous machines (LRE-IPMSMs), which combine the features of high electromagnetic performance as well as low cost, have attracted increasing attention in recent years [1]. The anti-demagnetization ability of the LRE-IPMSMs is crucial to the machine safety [2]. In [3], the tapered flux barriers are adopted to improve the anti-demagnetization ability of the LRE-IPMSMs. In [4], a practical analytical approach is proposed to express the direct link between the PM thickness and the demagnetization limit. In addition, the PM minimization is also a significant issue for the LRE-IPMSMs as it is crucial to decrease the machine cost. In [5], an analytical procedure is proposed to reduce the PM quantity in the LRE-IPMSMs without affecting the torque versus speed performance. In this paper, the demagnetization equivalent magnetic circuit (EMC) model of the investigated LRE-IPMSM is established and the effects of structure parameters on the PM flux density are investigated. The PM minimization design of the LRE-IPMSMs is obtained on the premise of no side effect on the machine output toque and anti-demagnetization ability.
62 citations
TL;DR: In this paper, a nonlinear hybrid field model was proposed to predict the open-circuit magnetic field distribution in surface-mounted permanent-magnet machines, where the saturation effect was accounted for in the CPM by considering the magnetic potential distribution on the stator bore.
Abstract: This paper presents a nonlinear hybrid field model to predict the open-circuit magnetic field distribution in surface-mounted permanent-magnet machines. It combines the complex permeance model (CPM) with the magnetic equivalent circuit (MEC). The saturation effect is accounted for in the CPM by considering the magnetic potential distribution on the stator bore, which is calculated by the MEC and can be transformed to the virtual current on the slot. The proposed model significantly improves the calculation accuracy for saturated machines, which is verified by the finite-element analysis and the experimental results.
51 citations
TL;DR: A current balancing method is proposed that can improve the current sharing between the paralleled phases relying on a single balancing transformer, and its theory is based on Ampere’s law, by forcing the sum of the three resonant currents to zero.
Abstract: Integrated magnetics is applied to replace the three-discrete transformers by a single core transformer in a three-phase LLC resonant converter. The magnetic circuit of the integrated transformer is analyzed to derive coupling factors between the phases; these coupling factors are intentionally minimized to realize the magnetic behavior of the three-discrete transformers, with the benefit of eliminating the dead space between them. However, in a practical design, the transformer parameters in a multiphase LLC resonant converter are never exactly identical among the phases, leading to unbalanced current sharing between the paralleled modules. In this regard, a current balancing method is proposed in this paper. The proposed method can improve the current sharing between the paralleled phases relying on a single balancing transformer, and its theory is based on Ampere’s law, by forcing the sum of the three resonant currents to zero. Theoretically, if an ideal balancing transformer has been utilized, it would impose the same effect of connecting the integrated transformer in a solid star connection. However, as the core permeability of the balancing transformer is finite, the unbalanced current cannot be completely suppressed. Nonetheless, utilizing a single balancing transformer has an advantage over the star connection, as it keeps the interleaving structure simple which allows for traditional phase-shedding techniques, and it can be a solution for the other multiphase topologies where realizing a star connection is not feasible. Along with the theoretical discussion, simulation and experimental results are also presented to evaluate the proposed method considering various sources of the unbalance such as a mismatch in: 1) resonant and magnetizing inductances; 2) resonant capacitors; 3) transistor on-resistances of the MOSFETS; and 4) propagation delay of the gate drivers.
48 citations
TL;DR: Compared to the only so far realized state-of-the-art reluctance force actuated fast steering mirror system with integrated sensors, the presented design enables to improve the product of range times’ bandwidth by more than 85%.
Abstract: This paper presents the design, assembly, and evaluation of a novel integrated two degree of freedom (2DoF) actuator design for tip/tilt motion and its integration into a fast steering mirror with comparably large range. The system is designed for scanning applications, such as in optical metrology systems, and comprises an integrated symmetric 2DoF hybrid-reluctance-force actuator and mover-flexure-design. The actuator design employs a permanent magnet for biasing the actuator with a constant flux and two actuator coils per axis to generate a steering flux for positioning the mover. The system prototype has an angular range of $\pm 3^\circ$ in tip and tilt and achieves a closed-loop control bandwidth of 1 kHz based on the signal of eddy current sensors. Compared to the only so far realized state-of-the-art reluctance force actuated fast steering mirror system with integrated sensors, the presented design enables to improve the product of range times’ bandwidth, representing a measure for the system performance, by more than 85%.
47 citations
TL;DR: The modeling, optimization, and validation of a hollow plunger type solenoid for high speed On/Off valve and the approved solution in Pareto front is selected by analytic hierarchy process and validated by the finite element analysis (FEA) method.
Abstract: This paper presents the modeling, optimization, and validation of a hollow plunger type solenoid for high speed On/Off valve. In the preliminary design, an accurate equivalent magnetic circuit model of the proposed solenoid is carried out, and the magnetic circuit is arranged in Kirchhoffs voltage law matrix form for the convenience of computer calculation. An iterative method is applied to obtain accurate permeability of the nonlinear magnetic material. To optimize the design parameters, a multiobjective optimization process is developed, and the multiobjective particle swarm optimization method is used to obtain the Pareto front of the desired objectives. An approved solution in Pareto front is selected by analytic hierarchy process and validated by the finite element analysis (FEA) method. A prototype based on the final optimized design is manufactured and tested. The experiment results verified the validation proposed design and optimization process.
47 citations
TL;DR: A novel closed-circuit magnetic navigation system (CMNS), which utilizes eight electromagnets connected by back yokes to maximize a magnetic field, is proposed and the mathematical assumption that the magnetic field generated from the proposed CMNS can be linearly proportional to the applied current is experimentally verified.
Abstract: We propose a novel closed-circuit magnetic navigation system (CMNS), which utilizes eight electromagnets connected by back yokes to maximize a magnetic field. We first show the effectiveness of a closed magnetic circuit (CMC) and conduct a parametric analysis to design a single CMC, which is utilized to construct the whole CMNS. A magnetic field mapping method is also developed utilizing the finite-element method and polynomial regression to evaluate and control the magnetic field over almost the whole workspace in real time. We investigated how the magnetic field changed based on the shape of core tips by comparing the isotropic magnetic field control authority, which is the ability to generate an equal magnetic field over the workspace regardless of the position and direction of the magnetic field. We experimentally verified the mathematical assumption that the magnetic field generated from the proposed CMNS can be linearly proportional to the applied current and that the magnetic field of the proposed CMNS can be expressed as a superposition of the magnetic fields generated by each electromagnet. Finally, we verified the effectiveness of the developed CMNS by performing experiments related to steering a commercial magnetic catheter.
44 citations
TL;DR: 3-D electromagnetic performances can be accurately predicted by the proposed analytical method and, with no need for the time-consuming 3-D FEA, differential evolution, a practical approach to global optimization, can simply be employed to search for solutions which belong to the Pareto optimal set.
Abstract: This paper presents a three-dimensional (3-D) performance analysis and multiobjective design optimization of coreless-type permanent magnet linear synchronous motors. The average of open circuit magnetic field distribution is analytically predicted by solving two Laplace's equations. The winding factor calculation, which requires an approach different from conventional slotted motors, is provided to evaluate the motor performances. As a result, average thrust and thrust ripple can be obtained without loss of accuracy compared with results of 2-D finite element analysis (FEA). The 3-D leakage influences are subsequently incorporated into the analysis using lumped parameter magnetic circuit model because end effects are not neglected due to a relatively large air gap. Consequently, two meaningful contributions of this paper are summarized as follows: first, 3-D electromagnetic performances can be accurately predicted by the proposed analytical method. Second, with no need for the time-consuming 3-D FEA, differential evolution, a practical approach to global optimization, can simply be employed to search for solutions which belong to the Pareto optimal set. Finally, the validity of the analytical results is confirmed with the experimental results.
TL;DR: In this article, a Ni-Mn-Ga single crystal placed inside a doubly wound coil with a primary and a secondary winding was used as a strain sensor, which was tested statically by compressing the element manually against a bias magnetic field perpendicular to the load axis.
Abstract: Deformation rearranges the crystal lattice in magnetic shape memory alloys, which changes all anisotropic properties of the material. This study investigates leveraging the deformation-induced change of magnetic permeability for a strain measurement technique. A Ni-Mn-Ga single crystal placed inside a doubly wound coil with a primary and a secondary winding was used as a strain sensor. An AC voltage excited the primary coil and the secondary voltage was measured as the sample was strained from 0 to 5.2%. This method varies from other methods that utilize complex magnetic circuits, require high magnetic fields, or other sensing methods such as Hall probes. When the sensor element was tested statically by compressing the element manually against a bias magnetic field perpendicular to the load axis, the voltage output varied from 129.7 mV to 164.2 mV. The dynamic performance of the sensor was tested by cycling the element between 25 and 100 Hz in compression against a bias magnetic field in a displacement controlled magneto-mechanical test system. The bias magnetic field was varied from 0.2 to 0.8 T (0.16 to 0.64 MA/m) while the cyclic displacement was varied from 0.5 to 4.5% strain. The voltage amplitude of the signal in the secondary coil increased with decreasing tensile strain. The full scale RMS voltage at a 200 mm stroke increased from 53.0 mV to 78.4 mV as the bias magnetic field decreased from 0.8T to 0.2 T. As the element was compressed, there was no difference in the sensor output voltage between the static and dynamic tests. When the element expanded during unloading, the voltage output of the sensor from the static test matched the voltage output during compression. For the dynamic testing, the voltage output of the sensor exhibited a hysteresis from the loading voltage output, the hysteresis increased when the strain rate increased.
TL;DR: An algorithm for the coupling of magnetothermal and mechanical finite element models representing superconducting accelerator magnets and a mesh-based interpolation method to exchange coupled quantities is presented.
Abstract: In this paper, we present an algorithm for the coupling of magnetothermal and mechanical finite element models representing superconducting accelerator magnets. The mechanical models are used during the design of the mechanical structure as well as the optimization of the magnetic field quality under nominal conditions. The magnetothermal models allow for the analysis of transient phenomena occurring during quench initiation, propagation, and protection. Mechanical analysis of quenching magnets is of high importance considering the design of new protection systems and the study of new superconductor types. We use field/circuit coupling to determine temperature and electromagnetic force evolution during the magnet discharge. These quantities are provided as a load to existing mechanical models. The models are discretized with different meshes and, therefore, we employ a mesh-based interpolation method to exchange coupled quantities. The coupling algorithm is illustrated with a simulation of a mechanical response of a standalone high-field dipole magnet protected with Coupling-Loss Induced Quench Technology.
TL;DR: Simulation and experimental results indicate that the proposed topology can achieve high torque density and high PM utilization factor simultaneously.
Abstract: In this paper, a new 6/10 hybrid switched reluctance motor (HSRM) is proposed. This original topology deploys permanent magnets (PMs) between adjacent stator poles of a divided teeth SRM. The function of the PMs is to weaken the magnetic saturation in stator poles, which is a major obstacle of torque improvement for divided teeth SRMs. Besides, the magnetic flux in the airgap increases as well. Hence, the output torque can be increased significantly. The flux distribution of the topology is analyzed by using an equivalent magnetic circuit. The topology is optimized by using the genetic algorithm for the best torque performance. Additionally, the characteristics of the proposed topology are compared with a 12/10 SRM, a 6/10 two-teeth SRM, a 12-slot, 10-pole three-phase six-state PM brushless DC motor, and a flux switching permanent magnet motor of the same dimension. A prototype of the proposed topology is built for experimental verification. The simulation and experimental results indicate that the proposed topology can achieve high torque density and high PM utilization factor simultaneously.
TL;DR: In this article, a novel heteropolar radial hybrid magnetic bearing (HRHMB) with low power loss is proposed for flywheel energy storage system, which can reduce the maximum control current to only 40% that of initial design by the optimizations.
Abstract: In this paper, one novel heteropolar radial hybrid magnetic bearing (HRHMB) with low-power loss is proposed for flywheel energy storage system. First, its structure and equivalent magnetic circuit (EMC) are introduced in detail. Then, some main design parameters are analyzed based on EMC, including air-gap bias flux density, magnetic pole area, permanent magnet (PM) dimensions, and control current. Furthermore, to improve the performances of the novel HRHMB, the optimizations are implemented both on its structure and some key size parameters, such as the second air-gap length, PM height, and width. Finally, the optimal scheme is verified by the 3-D finite-element analysis, which indicates the maximum control current can be reduced to only 40% that of initial design by the optimizations.
TL;DR: A distribution function to model the longitudinal end effect for the linear induction motors is developed to predict the variation of the air-gap flux distribution with the slip and the thrust and vertical force are calculated and compared with the existing model.
Abstract: In this paper, a distribution function to model the longitudinal end effect for the linear induction motors is developed to predict the variation of the air-gap flux distribution with the slip. The classic equivalent circuit model presented by Duncan is improved by taking the air-gap flux distribution function into account. First, the longitudinal air-gap flux and secondary demagnetizing current distribution function based on the travelling wave theory are proposed to describe the variation of the distributions. Second, an extra magnetizing branch, which takes the output power losses due to the longitudinal end effect into account, is connected in parallel with the existing magnetizing branch of the T-type circuit. Then, two coefficients used for correcting the magnetizing inductance and secondary resistance in the equivalent circuit are obtained. Third, the thrust and vertical force are calculated and compared with the existing model, as well as the efficiency and power factor in a range of rated speed is presented. Finally, these calculated results are validated by measurements on an experimental rig of the linear induction motor.
TL;DR: It is shown that the presented model is capable of effective modelling of the healthy and faulty machine under mentioned faults by a single model, thus reducing the computational complexity of the model.
Abstract: Magnetic-equivalent-circuit model for surface mounted permanent-magnet synchronous machines in both healthy and faulty cases is presented in this study, where both saturation effect and space harmonics are considered. Pole numbers, magnets and slot numbers can be chosen arbitrarily in the proposed model, and the behavior of the machine can be studied under various kinds of faults by a single model. Demagnetization, as well as inter-turn short short-circuit faults of the stator windings, are modelled, and a fault detection method is proposed. It is shown that the demagnetization fault is not detectible by stator current analysis, therefore an additional pole specific coil is considered in this study as a search coil. For modelling, the differential equations representing the electrical part of the PMSM model are converted into an algebraic type using the well-known trapezoidal technique and are solved simultaneously together with the non-linear magnetic equations using the Newton-Raphson method. It is shown that the presented model in this study is capable of effective modelling of the healthy and faulty machine under mentioned faults by a single model, thus reducing the computational complexity of the model. The effectiveness of the proposed MEC model is verified using finite-element method via Maxwell software.
TL;DR: It is shown that only noninvasive and online equipment can be used to diagnose SSGM and the viability of an operative wireless monitoring system on a 76-MW SSGM in an industrial environment is developed.
Abstract: This study presents an analytical and experimental method for detecting internal turn-to-turn short circuits both in the rotor or in the stator in salient pole synchronous generator machines (SSGM) connected to local power grid. Two main measurements are proposed to confirm or discard these electric faults: external magnetic field and external housing vibrations (EHV). In the event of a short-circuit winding fault, a correlation between external magnetic field and EHV is done to reinforce the diagnosis. Furthermore, the electric power injection dependence is analyzed and a noninvasive technique is proposed to determine the state of the SSGM whatever its load. Thus, it is shown that only noninvasive and online equipment can be used to diagnose SSGM. A diagnostic tool has been developed to show the viability of an operative wireless monitoring system on a 76-MW SSGM in an industrial environment.
TL;DR: 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-stators (DS) configurations that can achieve easy online PM magnetization control, excellent air-gap flux control, and acceptable torque capability.
Abstract: 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.
TL;DR: In this article, a novel magnetorheological (MR) damper with a meandering magnetic circuit, referred to as MMCMRD, is presented to improve the damping force performance of an MR damper.
Abstract: This paper presents a novel magnetorheological (MR) damper with a meandering magnetic circuit, referred to as MMCMRD, to improve the damping force performance of an MR damper. The magnetic flux path of the MMCMRD is guided by magnetically conductive and non-magnetically conductive elements. A theoretical model of the MMCMRD is built, and a finite-element analysis is performed to verify the principle of the MMCMRD. The damping force characteristics of the MMCMRD are experimentally tested on a hydraulic vibration system and compared with the theoretical results. The experimental results show that the controllable damping force of the MMCMRD under an excitation velocity of 0.0628 m/s is as high as 3400 N, which is considerably higher than that of the traditional MR damper. The equivalent damping and damping coefficient of the MMCMRD are both larger than those of the traditional MR damper when the input current exceeds 0.75 A. The research results show that the principle of the MMCMRD can improve the efficiency of the MR damper, and the damping force performance of the MMCMRD is accurately described by the theoretical model.
TL;DR: Results of the setup with the closed-loop HiL simulation are shown, which includes tests of the coil when generating a dynamic magnetic field and validation and results of the uniformity regarding the generated field around the system's center.
Abstract: This paper presents the detailed design, construction, and validation of a three-axis square Helmholtz coil. It also describes the methodology used to drive each pair of coils as well as the setup to operate it in a closed-loop system using a digital PID controller. The coil will be mainly used for aerospace applications, especially to aid the development and testing of attitude determination and control systems that use the earth's magnetic field as a reference vector. Most of the system was built using commercial components, reducing cost, and complexity compared to similar commercial systems. The assembled Helmholtz coil has approximately one cubic meter and can generate magnetic fields up to 2 G/ axis, keeping a uniformity of 0.04% around 11 cm of the center, in each axis. A custom-designed voltage-controlled current source, based on the Howland current pump, was employed, requiring no complex electronic circuits. The coil was designed to be part of a hardware-in-the-loop (HiL) system, which is controlled by a dSPACE modular simulation hardware and uses a commercial fluxgate magnetometer as the reference. This setup reduces the complexity of the proposed system when compared to similar ones. This paper presents two distinct results: first, there is the validation and results of the uniformity regarding the generated field around the system's center; second, results of the setup with the closed-loop HiL simulation are shown, which includes tests of the coil when generating a dynamic magnetic field.
TL;DR: In this paper, different screening solutions were used to shield the superconducting windings from the rotor field and the effectiveness of screening techniques for the stator coils and the impact on the machine performance and weight were evaluated for different stator designs, such as full stator core and air core with and without flux diverters.
Abstract: Hybrid electric propulsion has been identified as a potential solution to the ambitious environmental emissions and noise targets of the aerospace industry Superconducting machines may be the key component of that topology enabling the high power densities and efficiencies needed in aerospace Fully superconducting machines, however, are not a mature technology This paper looks at the different machine design configurations focusing on the stator magnetic circuit of a fully superconducting motor The motor has been designed for an aerospace distributed fan propulsion motor with an aerospace benchmark specification of 1 MW The AC fully superconducting machine includes superconducting bulk magnets mounted on a conventional rotor core and an MgB2 superconducting wire wound stator The AC losses in the stator winding are particularly sensitive to exposure to the main rotor field so different screening solutions were used to shield the superconducting windings from the rotor field The effectiveness of the screening techniques for the stator coils and the impact on the machine performance and weight were evaluated for different stator designs, such as full stator core and air core with and without flux diverters Various combinations of pole numbers, diverter geometries, and magnetic materials have been checked Results show that there is a tradeoff between stator iron losses and superconducting losses
01 Jan 2018
TL;DR: MEC models of proposed twelve-stator-slot and ten-rotor-tooth FSM with trapezoidal slot structure FSM corresponding to different rotor positions are combined as GRN and are solved utilizing incidence matrix methodology using MATLAB.
Abstract: Unique features of permanent magnet synchronous machines, conventional DC machines, and switched reluctance machines are combined in the form of Flux-Switching Machine (FSM). Magnetic saturation and complex structure of FSM compels designers to adopt numerical methods of analysis i.e. Finite Element Analysis (FEA). FEA is not preferred for initial design due to its computational complexity. Fourier analysis (FA) and Magnetic Equivalent Circuit (MEC) models are alternate analytical methods to analyze FSM. Results of FA for FSM are less accurate due to magnetic saturation. MEC models with Global Reluctance Network (GRN) methodology is a good compromise between accurate results and computational time, and is recommended for preliminary FSM design. In this paper, MEC models of proposed twelve-stator-slot and ten-rotor-tooth (12/10) with trapezoidal slot structure FSM corresponding to different rotor positions are combined as GRN and are solved utilizing incidence matrix methodology using MATLAB. Moreover, FSM flux simulations and no-load analysis were performed using JMAG software and validated with FEA. Comparison of results obtained from GRN methodology and corresponding FEA results shows errors less than ∼2%, hence validating accuracy of GRN methodology.
Abstract: This work proposes a novel type of tunable magnetorheological (MR) damper operated based solely on the location of a permanent magnet incorporated into the piston. To create a larger damping force variation in comparison with the previous model, a different design configuration of the permanent-magnet-based MR (PMMR) damper is introduced to provide magnetic flux dispersion in two magnetic circuits by utilizing two materials with different magnetic reluctance. After discussing the design configuration and some advantages of the newly designed mechanism, the magnetic dispersion principle is analyzed through both the formulated analytical model of the magnetic circuit and the computer simulation based on the magnetic finite element method. Sequentially, the principal design parameters of the damper are determined and fabricated. Then, experiments are conducted to evaluate the variation in damping force depending on the location of the magnet. It is demonstrated that the new design and magnetic dispersion concept are valid showing higher damping force than the previous model. In addition, a curved structure of the two materials is further fabricated and tested to realize the linearity of the damping force variation.
TL;DR: In this paper, a parametric linear magnetic equivalent circuit (MEC) was proposed for radial flux magnetic gears with surface permanent magnets. But the linearity approximation does not prevent the MEC from accurately matching the torque and air-gap flux densities predicted by a nonlinear finite element analysis (FEA) model for three diverse magnetic gear base designs.
Abstract: This is Part II of a two part paper on the development of a parameterized linear magnetic equivalent circuit (MEC) for radial flux magnetic gears with surface permanent magnets. Part I describes the MEC implementation. This section, Part II, evaluates the MEC model's accuracy by comparing its results against those produced by a nonlinear finite-element analysis (FEA) model. Simulation results demonstrate that the linearity approximation does not prevent the MEC from accurately matching the torque and air-gap flux densities predicted by a nonlinear FEA model for three diverse magnetic gear base designs. The impacts of the MEC discretization parameters introduced in Part I are also investigated using the same base designs, and guidelines for those settings are developed. Additionally, single design parameter sweeps illustrate the MEC's ability to track these changes over most practical design ranges and reveal where the MEC's accuracy degrades due to the linearity approximation. Finally, the results of a 46,656 case parametric optimization study demonstrate the MEC's ability to match the nonlinear FEA model's torque predictions within a few percent over a wide range of designs while achieving average simulation speeds 44 to 271 times faster than those of the FEA model.
TL;DR: The magnetic permeability of magnetorheological elastomers must be known for their long-term use in the actual engineering systems as mentioned in this paper, and the magnetic perceptivity of both isotropic and isotropically stable elastomer is known.
Abstract: The magnetic permeability of magnetorheological elastomers must be known for their long-term use in the actual engineering systems. In this article, the magnetic permeability of both isotropic and ...
TL;DR: In this paper, the authors compared different levels of detail of two-dimensional finite element (FE) models and investigated the impact of the modeling depth on the resulting copper loss to find a computation time optimized modeling setup.
Abstract: Analysis of ac effects, such as skin and proximity effect as well as the circulating currents and corresponding losses are usually done by finite-element analysis, while mostly only a single slot is considered, neglecting the influence of neighboring phases on the flux density of the stator iron and thus the resulting slot leakage flux. As the simulation of single stranded finite element (FE) models is computationally very demanding and time consuming, this paper compares different levels of detail of two-dimensional FE models and investigates the impact of the modeling depth on the resulting copper loss to find a computation time optimized modeling setup. It is shown that the use of single slot models is sufficient in case of distributed windings. Moreover, the potential increase of ac losses is assessed for two machines that are identical except for the stator winding, so that one and the same machine is investigated at two different voltage levels, namely 400 and 800 V. The reference machine is a 160 kW nominal power and 9000 r/min maximum speed permanent magnet synchronous machine. Since the magnetic circuit has to remain constant, both designs share the same overall winding scheme and total number of strands within a slot but differ in the number of parallel and serial connected strands. Due to the increased bundle cross section of the lower voltage winding, it is more susceptible to ac effects and thus tends to increased winding losses.
TL;DR: In this article, a magnetic spring was integrated into a linear oscillatory motor without any changes to the permanent magnet arrangement on the mover, which achieved the maximum energy storage capacity.
Abstract: 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.
14 Sep 2018
TL;DR: In this article, the IEM-formula has been used to model the effect of different grades of steel laminations on the performance of an electrical machine and its performance.
Abstract: The development of energy-efficient electrical machines requires an accurate knowledge of the soft- and hard-magnetic material behavior already in the design stage Accurate numerical models are required which offer the ability of better understanding and modelling in an appropriate accuracy With such model properties on the one hand accurate simulations can be performed and on the other hand the best possible material choice for a particular application, ie for an electrical machine, can be done The soft-magnetic material constitutes the magnetic core of an electrical machine and its properties On that account, the accurate prediction of iron losses of soft-magnetic materials for various frequencies and magnetic flux densities, ie, arbitrary magnetic field waveforms, is eminent for the design of electrical machines [1] For this purpose different phenomenological iron-loss models were proposed, which describe the loss-generating effects, ie, hysteresis, non-local eddy currents and anomalous eddy currents Most of these suffer from poor accuracy for not considering the effect of high frequencies and high material utilization as well as the material degradation due to the magneto-elastic coupling [2, 3, 5] This paper presents a comparison of common iron-loss models The IEM-formula used, resolves the limitation by introducing a high-order term of the magnetic flux density and considers the alteration of material-dependent loss-parameters due to the magneto-elastic coupling [3] The knowledge of the magnetic property deterioration due to induced residual stress occurring during the manufacturing or operation of the electrical machine is indispensable for the contemporary design It has been widely ascertained that processing of electrical steel laminations significantly alters the magnetic properties of the electrical steel [2–6] Cutting induces plastic deformation and residual stress in the laminations Due to their strong sensitivity to mechanical stress, the magnetic properties are locally degraded near the cut edge The extent of the degradation depends substantially on the process characteristics, ie, the cutting procedure and cutting parameters in combination with material properties, such as mechanical strength and grain size [4–6] In [7] a continuous material model for an efficient numerical model of the local magnetization was introduced By replacing numerically expensive sliced models, the continuous model (CM) is independent of the discretization and converges in the case of coarse meshes to the sliced model [7] Measured single-sheet specimens are used to identify the different model parameters In Fig 1 results on hysteresis loss distribution are presented The vital advantage of the proposed CM is that properties depend only on the distance to the cut edge For improved estimation of penetration depth and mechanical stress distribution, novel experimental procedures are utilized [8] and mechanical simulations are evaluated [6] to further advance the cut-edge model Permanent magnets are central to the electromagnetic energy conversion process in permanent-magnet synchronous and flux-switching machines In order to design the magnetic circuit and a magnetizing circuit for post-assembly magnetization as well as to analyze the resistance to being demagnetized during the simulation of electrical machines, it is indispensable to describe the magnetization behavior of the permanent magnets accurately However, due to the complex interplay of the non-linear and hysteretic magnetization behavior and the magnetic anisotropy, it is a complex problem Commonly, simplified models are used, which are based on empirical and phenomenological approaches These describe the major loop of the permanent magnets only However, the magnetization state of the permanent magnet depends on the magnetic and thermic history, ie, it is indispensable to account for minor loops or incompletely magnetized permanent magnets In this paper, a pragmatic methodology to replicate the hysteresis of permanent magnets is presented, which uses first-order return curves and the magnetization behavior starting from the virgin state for model-parameter identification [10] Efficient parametric models with low additional computational effort are perfectly suited for the finite-element analysis Starting from these advanced models of soft- and hard-magnetic materials, a methodology for selecting the optimal steel grade during the design-stage of electrical machines in due consideration of the application-specific requirements on torque-speed operating points, ie, all have to meet the requirements of the same driving cycle, is presented [1] This allows one to study the effect of different electrical steel grades on the operational characteristics along the torque-speed map [11] In order to determine the efficiency of each combination of machine topology and lamination type, the iron-loss model with material degradation is used in combination with a machine simulation scheme of the entire operating range of the machine In the light of this, this paper will give an overview on the current modeling approaches applied at the Institute of Electrical Machines (IEM) for soft- and hard-magnetic materials in the simulation of rotating electrical machines
TL;DR: In this article, perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nanopillars with a smooth linear resistance dependence with both the in-plane magnetic field and DC bias.
Abstract: In this paper, perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nanopillars with a smooth linear resistance dependence with both the in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is important for rectification in wireless charging and energy harvesting applications. By carefully balancing the amount of PMA acting in the free layer, the measured RF to DC voltage conversion efficiency can be made as large as 11%.In this paper, perpendicular magnetic anisotropy (PMA) is tailored by changing the thickness of the free layer with the objective of producing MTJ nanopillars with a smooth linear resistance dependence with both the in-plane magnetic field and DC bias. We furthermore demonstrate how this linear bias dependence can be used to create a zero-threshold broadband voltage rectifier, a feature which is important for rectification in wireless charging and energy harvesting applications. By carefully balancing the amount of PMA acting in the free layer, the measured RF to DC voltage conversion efficiency can be made as large as 11%.