Showing papers presented at "IEEE Conference on Electromagnetic Field Computation in 2022"

Data-driven sparse discovery of hysteresis models for piezoelectric actuators

Abstract: This paper proposes a new approach to model hysteresis in piezoelectric actuators based on recent advances in sparsity promoting machine learning methods. While sparse regression has successfully modelled several phenomena in sci-ence and engineering, its performance in modelling the nonlinear hysteresis behaviour in piezoelectric materials is still unexplored. This study applies the sequential threshold least-squares (STLSQ) algorithm to discover the governing hysteresis expressed in the form of a dynamical system. It is found that a parsimonious model governing the dynamics is extracted from a large candidate library, which predicts the hysteresis efficiently with less than le-3 relative percent error, demonstrating the algorithm's efficiency.

Optimization of Permanent Magnet Configuration Using Boolean Geometry Projection Method for IPM Motors

Abstract: This paper proposes a novel optimization method, Boolean geometry projection method, for the determination of permanent magnet configuration in interior permanent magnet motors. In the proposed optimization, the magnet configurations are freely modified without the upper and lower limits of shape parameters that have to be carefully determined by users. It is shown that the proposed method leads to the torque performance better than that obtained by conventional approaches.

A Numerical Twin Model for the Coupled Field Analysis of TEAM Workshop Problem 36

Abstract: A numerical twin model for the magneto-thermal analysis of an induction heating device is proposed. The nonlinearity of magnetic permeability against temperature - which characterizes the workpiece - is captured by the model, while the use of a Convolutional Neural Network (CNN), trained by a number of finite-element analyses, makes it possible to reconstruct the temperature field map in the workpiece region. TEAM problem 36 is recalled as the case study.

Optimal Terminations of 2D Meta-Surfaces for Uniform Magnetic Field Applications

Abstract: This paper investigates the possibility of governing the distribution of the currents in a 2D metamaterial realized with magnetically coupled-resonant circuits, with the goal of obtaining a uniform magnetic field in the proximity of the structure. The currents are controlled terminating the boundary of the metasurface with proper additional impedances, whose values are calculated by means of an optimization procedure. The behaviour in terms of magnetic field is then discussed.

Physics- Informed Neural Networks for Inverse Electromagnetic Problems

Abstract: PDE-constrained inverse problems are very common in electromagnetism, just like in other engineering fields. Their ill-posedness (in the sense of Hadamard) makes their solution non-trivial, also taking into account that solving PDEs could be computationally intensive. In this context, first, we will introduce three frameworks that concern surrogate models and physics-informed neural networks (PINNs). Second, we will show the capability of a PINN in solving an ill-posed direct problem. In fact, PINNs are designed to be trained to satisfy the given training data as well as the relevant governing equations. This way, a neural network can be guided with training data that do not necessarily need to be complete.

Calculation Method and Application of Magnetostrictive Vibration of Wound Core

Abstract: Different from laminated iron core, this paper proposes a new three-dimensional vibration calculation method for ultra-thin silicon steel wound core and takes anode saturable reactor core as the calculation object. The correctness of this three-dimensional calculation method is proved by building an experimental platform.

Utilizing Helicoidal and Translational Symmetries Together in 2-D Models of Twisted Litz-Wire Strand Bundles

Abstract: Increasing operating frequencies require even more detailed models of litz-wire windings. In this paper, a helicoidally symmetric model of a twisted strand bundle is studied. The distance at which the produced magnetic field looks translationally symmetric is obtained. A measure for the symmetricity of a field is proposed. This enables the coupling of helicoidally symmetric and translationally symmetric models with good understanding of the introduced approximation error.

Optimal Design of PMa-SynRM for Electric Bicycle Traction Motor Using Adjustive-resolution Robustness Optimization Algorithm

Abstract: This paper proposes adjustive-resolution robustness optimization algorithm (AROA) for robust optimal design of electric bicycle (EB) traction motor. Target motor is permanent magnet assisted synchronous reluctance motor and design objectives are average torque, torque ripple, cogging torque, and total harmonic distortion of the line-to-line back electromotive force. The AROA can consider various objectives at the same time using the weighted sum method, and the designer can assign the desired weight according to the model. The proposed algorithm can drastically reduce the number of function calls by interpolating problem regions. Additionally, the AROA proposes novel initial sampling strategy, diversification strategy, intensive searching strategy to effectively adjust the number of generated samples. At the end of the algorithm, robustness test is conducted, and robust optimal solution is determined considering the accuracy of the interpolated uncertainty band of both global and local solutions. The superior performance of the AROA was verified at two mathematical test functions, and the applicability of the practical motor design was verified by applying the AROA to the optimal design of the EB traction motor and successfully deriving the robust optimum design. The accuracy of the analysis was confirmed by manufacturing the prototype motor and comparing the experimental results.

Generalizable DNN based multi-material Hysteresis Modelling

Abstract: This The effective representation of material properties is fundamental to the simulation of electromagnetic devices such as electrical machines, actuators, sensors, transformers, etc. However, the actual operating point of a material is dependent both on position within the device and the excitation. Every point in an electrical machine can be operating on a different part of the magnetization curve. To determine performance parameters such as the efficiency of the machine, the hysteretic behavior of the material is crucial, and the representation used can impact the performance of a simulation code. In this paper, the use of deep learning methods is proposed to reduce the computational effort needed to implement hysteresis in a finite element based simulation system.

Research on Electromagnetic System of Large Capacity Energy Storage Flywheel

Abstract: A large capacity and high power energy storage flywheel system(FESS) is developed and applied to wind farms in this paper, focusing on the high efficiency design of the key electromagnetic components of the FESS, i.e motor/generator, radial magnetic bearing(RMB) and axial magnetic bearing (AMB). Firstly, a axial-flux permanent magnet synchronous motor (AFPMSM) based on soft magnetic composite material (SMC) is designed and its electromagnetic field is analyzed by FEM. Then, considering the structure of FESS and motor, a permanent magnet biased radial magnetic bearing (PMRMB) and a HALBACH axial permanent magnetic bearing(PMAMB) is proposed. They have the advantages of low power consumption and large bearing capacity. Finally, the flywheel was made and its performance was tested.

Transient Modelling of Corrosion Protection Systems with BEM-Electrical Circuit Hybrid Model

Abstract: Modelling of corrosion protection systems in seawater is classically based on Boundary Element Method (BEM) with a limitation to static studies. This paper presents an original transient approach hybridizing BEM and circuit solving, enabling the modelling of more complex system and interface phenomena.

Development of a FE Reduced Model on a Large Operating Range for a Squirrel Cage Induction Machine in Non Linear Case

Abstract: Numerical simulation of nonlinear magneto-quasistatic problems based on the Finite Element (FE) method can lead to significant computational times. Then, Model Order Reduction (MOR) approaches based on the Proper Orthogonal Decomposition (POD) alleviates the issue, by projecting the FE model onto a reduced basis. The accuracy of a reduced model depends on the choice of the reduced basis. In this communication, a methodology for the construction of the reduced model of a squirrel cage induction machine in the non linear case is proposed, valid on the whole operating range of the machine. The accuracy of the reduced model is evaluated for global quantities of interest.

A Study on a Ferrite Spoke-type Permanent Magnet Synchronous Motor with Improved Post-assembly Magnetization Performance

Abstract: For the high efficiency of electric motors, research on electric motors using permanent magnets has been conducted. However, rare earth permanent magnets are difficult to obtain due to the scarcity of resources, and the price is very high. As a solution to this problem, research on spoke-type PMSM has been conducted. Furthermore, research on Double Spoke-type PMSM, an upgraded version of the conventional spoke-type PMSM, was conducted. This electric motor has a high output density by simultaneously utilizing the magnetic torque and the reluctance torque. However, the aforementioned motors have the disadvantage that post-assembly magnetization is difficult. This paper conducted a study to solve the above problem.

2D Eddy Current Boundary Value Problems for Power Cables with Helicoidal Symmetry

Abstract: Power cables have complex geometries in order to reduce their AC resistance. The cross-section of a cable consists of several conductors that are electrically insulated from each other to counteract the current displacement caused by the skin effect. Furthermore, the individual conductors are twisted over the cable's length. This geometry has a non-standard symmetry - a combination of translation and rotation. Exploiting this property allows formulating a dimensionally reduced boundary value problem. Dimension reduction is desirable because otherwise the electromagnetic modeling of these cables becomes impracticable due to tremendous computational efforts. We investigate two-dimensional eddy current boundary value problems which still allow the analysis of three-dimensional effects, such as the twisting of conductor layers.

Interpolation of Measured Hysteresis Loops for Proper Construction of the Everett Map

Abstract: The Everett map is a component used by the Preisach model that stores the hysteresis behavior of soft-magnetic materials, and allows for accurate modeling of hysteresis loops when properly constructed. It is created from scattered data points, obtained from a set of magnetic measurements, that need to be interpolated for usage in the Preisach model. The generic approach for interpolation, based on Delaunay triangulation and polynomial or spline surface fits, introduces artifacts in the modeled hysteresis results, due to low quality triangulation or oscillations. Therefore, this work presents a different method of interpolating the measured data to construct the Everett map without impacting its accuracy.

Analysis of Magneto-Mechanical Coupling Model of Anodic Saturable Reactor Considering Anisotropy with UHVDC Converter Valve

Abstract: As a vital component in the converter valve of Ultra-high Voltage (UHV) DC transmission, the anodic saturable reactor is often affected by the effect of magnetic, thermal and stress field in actual operation, so the simulation under ideal circumstances cannot accurately evaluate the performance of the reactor. In order to simulate the complex effect of magnetic and mechanical field, a coupled finite element model of the anodic saturable reactor core considering anisotropy is established, which includes electromagnetic anisotropy parameters, mechanical anisotropy parameters and magneto-mechanical coupling parameters. Besides, the vibration testing platform is built. The magnetic flux density and vibration acceleration are measured at different magnetic induction intensity levels of the core. The reasons for the difference between simulation and measurement results are analyzed. This research is helpful to increase the accuracy of calculation in the magneto-machine coupling simulation research of electrical equipment and provide reference for the optimization direction of magneto-machine coupling model.

Characteristic Analysis and Verification of Electromagnetic Force for Armature of the Electromagnetic Rail Launcher

Abstract: In this paper, the armature electromagnetic force of the electromagnetic rail launcher is taken as the research object, and the electromagnetic field control equation considering the influence of armature movement velocity and the armature dynamic equation considering the influence of resistance are given. Then, the finite element calculation model of the electromagnetic rail launcher is built, and the correctness of the model is verified by data comparison. Finally, the trapezoidal excitation current is used to further analyze the dynamic characteristics of the armature electromagnetic force under the influence of different factors. The research results have important guiding significance for the study of the dynamic characteristics of the electromagnetic rail launcher under the actual working conditions and the refined design of the pivot rail structure.

Rotor Design for Improving the Maximum Inertia and Power Factor in Line-Start Synchronous Reluctance Motor

Abstract: In this paper, the design and analysis of a line-start synchronous reluctance motor (LS-SynRM) is performed considering the maximum inertia and power factor. Because LS-SynRM must be operating the synchronous speed, the capability of load synchronization is important for the various industrial application. The electromagnetic and mechanical transient analysis of a finite element analysis (FEA) is used to analyze the maximum load inertia. Furthermore, because the power factor is also important index in the industrial application according to IEC 60034–1, the bridge design is performed considering the power factor and mechanical stress. Based on the basic model, the optimal design is performed to improve the power factor. The design parameters, constraints, and objective functions are considered to optimization of LS-SynRM. Finally, the optimal model of LS-SynRM is manufactured, and experiment is performed to verify FEA result.

Optimal Design of Surface-mounted Permanent Magnet Synchronous Motor for Robot Joint using Subdomain-Subdivide Assisted Method

Abstract: This paper deals with the optimal design of SPMSM for robot joints using subdomain-subdivide assisted method (SSAM). SSAM is a multi-objective optimization algorithm that can simultaneously consider various objective functions. A meta model is used to solve the problem of calculation time, which is a problem of existing algorithms. In addition, the periphery of the predicted solution is defined as subdomain and subdomain is subdivided to increase the accuracy of the solution. This method has the effect of shortening the interpretation time as well as the accuracy of the solution because it does not subdivide the entire area. In the optimal design of SPMSM, design variables sensitive to objective functions are extracted using the Taguchi method and applied to the proposed algorithm. As a result, it was confirmed that the electromagnetic characteristics of the optimal model were superior to the initial model.

Electromagnetic Calculation of Tubular Permanent Magnet Linear Oscillation Actuator Considering Corrected Air Gap Permeance

Abstract: Tubular permanent magnet linear oscillation actuators (TPMLOA), with the simple structure and convenient control, have been paid extensive attention in the field of compressors and industry applications. In this paper, an electromagnetic calculation method of the TPMLOA is proposed. Firstly, a novel topology of the TPMLOA is introduced. Then, based on the radially laminated stator, the actual air gap permeance is derived by the flux tube method. Finally, the electromagnetic characteristic of the TPMLOA is analyzed by 2-D finite-element analysis (FEA) considering the corrected air gap permeance, and the results is compared with the 3-D FEA results. Additionally, for verifying the accuracy of the calculated results, a prototype of the TPMLOA is manufactured and tested.

Analysis and Prediction of Mid-high Peak Frequencies for Microspeaker with Side-firing Front Chamber

Abstract: In this paper, the generating mechanism of mid-high frequency peaks of sound pressure level are investigated theoretically with side-firing front chamber. The mid-frequency peak is caused by the Helmholtz resonance phenomenon of front chamber and high-frequency peak occurs due to the tube resonance. Electromagnetic-mechanical-acoustical coupling method (E-M-A) and resonance equations are used to obtain the sound pressure level and peak frequencies, respectively. The microspeaker samples with different front chamber designs have been manufactured to verify the analysis results. The comparisons show good agreement between analysis results and experimental results.

Dual Magnetostatic Formulations for Problems having General Boundary Conditions

Abstract: Dual formulations are more reliable and accurate in computing energy-related global quantities such as inductances and capacitances by providing the upper and lower bounds of the true values of the global energy-related quantities. Existing dual formulations adopt different variables belongs to totally different finite element spaces and thus will produce totally different algebraic matrix equations to be solved separately. In this work, two recently proposed dual formulations for open region problems where the coefficient matrices are exactly the same, are generalized to solve problems with general boundary conditions for cases with reduced full model or other scenarios. Two numerical examples are computed to show the accuracy of the proposed formulations.

Combined Random Forest and Genetic Algorithm for Optimal Design of PMa-SynRM for Electric Vehicles

Abstract: This paper proposes a method combining random forest technique (RF) and genetic algorithm (GA) for optimal design of traction motors for electric vehicles (EVs). The target motor is the permanent magnet assistant synchronous re-luctance Motor (PMa-SynRM) and the design goal is increasing the average torque and efficiency and reducing torque ripple and the total harmonic distortion of line-to-line back elec-tromotive force. The prediction accuracy of the RF was im-proved through hyperparameter tuning and verified through several test functions. The applicability of the proposed method is verified by deriving the optimal design of PMa-SynRM for EVs and improving the target motor performance.

Optimization of Corrugated Horn Antenna Fabricated by Additive Manufacturing and Plating

Abstract: This paper presents multi-objective optimization of corrugated horn antennas fabricated by additive manufacturing (AM) and plating. AM and plating can fabricate 3D structures, but there are technical limitations. The shape of corrugated horn antenna is optimized to account for AM and plating limitations in order to maximize antenna gain and minimize cross polarization.

High-Strength Rotor Optimization of High-Speed Permanent Magnet Synchronous Motor for Hydrogen Recirculation Pumps

Abstract: In this paper, a high-speed permanent magnet synchronous motor (PMSM) is designed and manufactured for hydrogen recirculation pumps (HRPs). The motor rotor is exposed to a high-pressure mixture of steam and hydrogen, which makes hydrogen embrittlement occur in permanent magnets (PMs). A protective coating process is necessary for the PMs in high-pressure hydrogen. However, in the process of sleeve interference installation, the protective coating of the PMs is easily damaged. This paper aims at the high-strength rotor optimization of high-speed PMSM for HRPs in terms of electromagnetic and mechanical performance. A new sleeve structure is proposed to strengthen the motor rotor considering the manufacturing process. The electromagnetic performance is optimized by adjusting the ratio of PMs with different magnetization directions with the different sleeve structures. A 25000r/min 800W prototype has been manufactured and the experimental results validate the analysis methods in this paper.

Core Loss Analysis of Soft Magnetic Composites Based on 3D Modeling under Non-sinusoidal Excitation

Abstract: Based on the existing soft magnetic composite (SMC) finite element models, three-dimensional(3D) finite element simulation models of SMC single particle and magnetic ring sample were established in this paper. In view of the fact that the existing finite element models do not take into account the effect of harmonics on the hysteresis loss of SMC, based on the hysteresis loss calculation formula of Bertotti loss separation theory, an improved expression of hysteresis loss coefficient is derived by introducing the correction factor of loss coefficient. And it is applied to the model so that the model can be used to calculate the magnetic core loss under non-sinusoidal excitation. Finally, the feasibility and effectiveness of the proposed model are verified by comparing with experimental results.

Novel AC-Field Hybrid Excitation DC Generator with Spoke-Type Segmented- PMs Rotor

Abstract: This paper proposes a novel AC-field hybrid excitation DC (AC-HEDC) generator, in which the AC field winding is located on the stator to achieve brushless excitation. The spoke-type permanent magnet (PM) rotor is employed to improve the flux per pole and thus the power density due to its strong flux-focusing effect. Furthermore, the spoke-type PMs segmented by multilayer flux bridges are designed to obtain the parallel path of PM flux and field excitation flux, which is beneficial for the flux regulation and the reduction of eddy loss and demagnetization risk of PMs. Then, the electromagnetic performance of the proposed AC-HEDC generator with spoke-type segmented-PMs (SS) rotor (i.e, AC-SSHEDC generator) including voltage regulation capability, output voltage-current characteristic, loss, efficiency and demagnetization withstand capability are investigated according to different number of segmented-PMs. It is demonstrated that the proposed AC-SSHEDC generator can achieve wide range of constant output voltage, low iron loss and demagnetization risk.

Study on Eddy Current Loss of Permanent Magnet and Performance Improvement in Low-speed High-torque Permanent Magnet Synchronous Motor

Abstract: The stator slot of low-speed high-torque permanent magnet synchronous motor (LHPMSM) is generally designed as straight slot, due to the need of wire embedding process, which will introduce a large number of tooth harmonics. At the same time. Tooth harmonics worsen the eddy current loss of permanent magnets(PMs), leading to continuous temperature rise, demagnetization of PMs, and affecting the working performance of motor. In this paper, a slot wedge made of composite material is proposed and a magnetic insulation slot is introduced into the rotor. The optimized model not only decreases the eddy current loss, but also improves the electromagnetic performance of LHPMSM.

Magnetic Flux Density Calculation Accuracy Improvement Of Edge Finite Element Based On Superconvergent Patch Recovery Method

Abstract: In this paper, the Superconvergent Patch Recovery method (SPR) is applied to the electromagnetic field calculation problem. On the basis of the double curl equation of vector magnetic potential, the magnetic flux density is solved by the edge finite element method using the tetrahedral mesh. According to the Superconvergent Patch Recovery technology of finite element method, all elements around the certain element are formed into element group. By the interpolation of the superconvergence point field intensity in the element, the calculation accuracy of magnetic flux density is improved.

Topology Optimization of Electromagnetic Devices with Movable Magnetic Path under Fixed Amount of Materials

Abstract: This paper proposes a new topology optimization method for electromagnetic devices with movable magnetic path under the fixed amount of materials. The amount is preserved strictly on the basis of a new hybrid encoding (binary and per-mutation encoding). A new variable magnetic path is successfully obtained by optimizing the material distributions several times.