Equivalent Magnetic Circuit Network Method Research Articles

Analytical Calculation of Air-Gap Magnetic Field Distribution in IPMSMs with Mixed Eccentricity Accounting for Bridge Saturation

This paper presents an analytical model for calculating the detailed air-gap magnetic field distribution in interior permanent magnet synchronous motors (IPMSMs) with mixed eccentricity. In order to improve the efficiency of model solving, a modeling strategy combining the equivalent magnetic circuit network method and the subdomain method was adopted. Specifically, the magnetic field distribution of the rotor was modeled by using the magnetic circuit analysis method, and the magnetic field distributions of the air-gap, slot opening and stator slot along the radial direction were modeled in different regions according to their structure ruler. Then, the influence of bridge saturation was considered. Moreover, based on the analysis of the air-gap geometric structure with mixed eccentricity, a detailed spatiotemporal analytical model of the air-gap magnetic field was established, which provides a more accurate description of the mixed eccentricity composed of static and dynamic rotor eccentricities of different severity. The analytical models were compared with the corresponding models established by the finite element method, which proved the accuracy and validity of the models established in this paper. Finally, some key features related to radial and tangential air-gap flux density were extracted, which can significantly reflect the characteristics of eccentricities. The main findings reported in this paper will be of benefit for developing methods for early identification and diagnosis of eccentricity faults in IPMSMs.

Design of Hybrid Magnetic Stage for a Magnetic–Pneumatic Levitation System

This article presents a magnetic–pneumatic levitation system for gravity offload system of large deployable mechanisms, which combines the attractive force of magnetic stage and thrust force of air-bearing and is characterized by inner stability. The article focuses on the design of the hybrid magnetic stage. The equivalent magnetic circuit network method is used to analyze the electromagnetic (EM)-permanent hybrid magnetic field, the distribution of magnetic flux density of the air gap is solved, and then the magnetic force is obtained. To improve the design efficiency, the two-step design is adopted. First, the air gap is determined by sweeping the reluctance ratio to reduce the influence of parameter deviation of cast iron on the magnetic force. Then, the other parameters of the hybrid magnetic stage are optimized based on the multi-objective particle swarm optimization (MOPSO) algorithm. Through the comparison between the results of finite-element simulation and prototype experiments, the accuracy of the model is verified, and the expected design goal is achieved.

Load noise prediction of a power transformer

In this article, we propose a new regression equation to predict the noise of a power transformer based on the winding vibration under a loading condition. A regression between load noises and tank vibrations for multiple transformers with different rated powers was confirmed through measurements and regression analysis. A regression equation for load noise and winding vibration was derived considering the fact that the winding vibration level is proportional to the tank vibration level. The electromagnetic force, which is the excitation force of the winding, was obtained using the equivalent magnetic circuit network method to obtain the winding vibration required for the regression equation. Subsequently, the obtained force was applied to a finite element model for the winding to achieve the vibration response. The winding vibration obtained through these methods is closely correlated with the load noise, and the amount of winding vibration transferred to the tank could be changed according to the distance between the tank and the winding. Accordingly, an equation for predicting the load noise was established considering the winding vibration and the correlation factors according to the distance of the transmission path. The proposed prediction equation is considerably more accurate than the previous prediction equation.

Three-Dimensional Equivalent Magnetic Circuit Network Method for Precise and Fast Analysis of PM-Assisted Claw-Pole Synchronous Motor

Permanent magnet (PM) assisted claw-pole synchronous motor (CPSM) has commonly been used in a variety of industrial applications thanks to its robust structure and high energy density. However, such a motor has an axially asymmetric rotor configuration, which induces the corresponding 3-D magnetic field distribution. Thus, this paper proposes an infinitesimal hexahedron-element-based 3-D equivalent magnetic circuit network (EMCN) method in order to estimate the performance of the PM-assisted CPSM. The hexahedron element is considered an optimum unit element in describing the configuration of the PM-assisted CPSM in detail. That eventually makes it possible to evaluate the specific 3-D magnetic field distribution from which the flux linkage, the back-electromotive force, and the torque are also being calculated. The 3-D EMCN results are compared with 3-D finite element analysis (FEA) data and/or experimental data to validate their accuracy. Finally, it is proved that the scalar-potential-based 3-D EMCN method requires less computing time than the vector-potential-based 3-D FEA.

Magnetic field analysis of a coaxial magnetic gear mechanism by two-dimensional equivalent magnetic circuit network method and finite-element method

Non-contact magnetic gears offer unique features: no mechanical loss, no mechanical fatigue, overload protection, high efficiency, precise peak torque transmission, tolerance of misalignment, isolation of vibration and low acoustic noise, which overcome the inherent disadvantages of existing mechanical gears. Among the various types of magnetic gear mechanisms, the coaxial magnetic gear mechanism improves the utilization of permanent magnets to generate a high transmitted torque, which has been receiving more and more attention in recent years. This paper presents a two-dimensional (2-D) equivalent magnetic circuit network method to predict the magnetic field distribution of a coaxial magnetic gear mechanism. The topological structure, working principle and speed reduction ratio of an existing coaxial magnetic gear mechanism are introduced first. A 2-D equivalent magnetic circuit network method is then proposed to calculate the radial components of the magnetic flux densities within the inner and outer rotors. 2-D finite-element analysis (FEA), undertaken by applying commercial FEA software Ansoft/Maxwell, confirms the validity and effectiveness of the proposed analytical model. A 2-D equivalent magnetic circuit network method can be provided as an effective tool for the magnetic field analysis and optimal design of coaxial magnetic gear mechanisms.

Performance Comparison of the Railway Traction IPM Motors between Concentrated Winding and Distributed Winding

This paper presents performance comparison between concentrated winding and distributed winding of IPMSM (Interior Permanent Magnet Synchronous Motors) which is recently used for lightweight railway applications. Motors are designed on various schemes and analyzed by using FEM (Finite Element Method) instead of EMCNM (Equivalent Magnetic Circuit Network Method) in order to take into account saturation and non-linear magnetic property. The overall performance such as torque, torque ripple, losses, demagnetization, efficiency, power density and so on are investigated in detail at the rated and maximum operating speed. The results of the analysis found that both concentrated and distributed winding IPMSMs are promising candidates for high power railway traction motor

집중권을 시행한 영구자석 매입형 동기전동기의 철손 저감

집중권 방식의 견인용 영구자석 매입형 동기전동기(IPMSM)는 출력밀도의 관점에서 우수하나 심각한 영구자석 와전류 손실을 가지고 있다. 본 논문에서는 영구자석 매입형 동기전동기의 자기적 특성을 분석하여 V-타입 회전자 영구자석의 각도와 폭을 변경함으로써 철손을 최소화하는 최적설계를 수행하였다. 자성체의 비선형성을 고려하기 위하여 자기등가회로법 대신 유한요소법을 이용하였으며, 각 파라메타가 영구자석에 발생하는 철손에의 영향 및 파라메타간의 교호작용을 파악하기 위하여 시뮬레이션 기반의 실험계획법을 사용하였다. 이를 통하여 모터의 성능을 유지하면서 철손을 상당히 줄인 집중권 방식의 영구자석 매입형 동기전동기의 최적설계를 반응표면법을 이용하여 도출하였으며, 유한요소법을 이용하여 이를 검증하였다. Interior Permanent Magnet Synchronous motors (IPMSM) with concentrated winding are superior to distributed winding in the power density point of view. But it causes huge amount of eddy current losses on the permanent magnet. This paper presents the optimal permanent magnet V-shape on the rotor of an interior permanent magnet synchronous motor to reduce the core losses and improve the performance. Each eddy current loss on permanent magnet has been investigated in detail by using FEM (Finite Element Method) instead of equivalent magnetic circuit network method in order to consider saturation and non-linear magnetic property. Simulation-based design of experiment is also applied to avoid large number of analyses according to each design parameter and consider expected interactions among parameters. Consequently, the optimal design to reduce the core loss on the permanent magnet while maintaining or improving motor performance is proposed by an optimization algorithm using regression equation derived and lastly, it is verified by FEM.

Comparisons Between Various Designs of Transverse Flux Linear Motor in Terms of Thrust Force and Normal Force

We present comparisons between different kinds of transverse flux linear motor (TFLM) with various configurations of permanent magnet (PM) including without PM, side PM, and full PM in its structure. We compare one-phase and three-phase systems. All the comparisons are based on the thrust force and normal force that are derived from using the three-dimensional equivalent magnetic circuit network method. Models with side PM and three phases offer good performance of TFLM in terms of thrust force and normal force. The experimental results show good agreement with the analytic results.

Optimum Design of Transverse Flux Linear Motor for Weight Reduction and Improvement Thrust Force Using Response Surface Methodology

Permanent magnet (PM)-type transverse flux linear motors (TFLMs) are electromagnetic devices which can develop directly powerful linear motion. The unique configuration makes power of output higher than longitudinal motors, but also it makes characteristic analysis difficulties. This paper deals with an effective analysis of PM-type TFLM by 3-D equivalent magnetic circuit network method (EMCNM). This paper presents optimum design of PM-type TFLM to reduce the weight of the machine with the constraints of thrust and detent force using response surface methodology (RSM). RSM was well adapted to make the analytical model of the minimum weight with constraints of thrust and detent forces and enable the objective function to be easily created and a great deal of the time in computation to be saved. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of electric machines.

Determination of Parameters Considering Magnetic Nonlinearity in Solid Core Transverse Flux Linear Motor for Dynamic Simulation

This paper presents methods to calculate motor parameters considering magnetic nonlinearity in solid core transverse flux linear motors (TFLM) for dynamic simulation. The magnetic field characteristics of the machine are analyzed by using 3-D equivalent magnetic circuit network (3-D EMCN) method, and parameters for dynamic simulation such as linkage flux, thrust, attraction force, and core loss are calculated by using the magnetic field analysis results. The calculated parameters are used as a form of lookup table in the dynamic simulation model. The accuracy of the method is examined by the comparison of input currents which are calculated by using the dynamic simulation model and measured for an example TFLM.

Parametric Design for Superconducting Synchronous Motor With 3D Equivalent Magnetic Circuit Network Model

This paper proposes an effective parametric design for high temperature superconducting (HTS) synchronous motors with 3D equivalent magnetic circuit network (EMCN) method. Proposed design process consists of 5 steps which are electric design, mechanical design, characteristic analysis for field and armature, and motor characteristic analysis. Especially, in order to predict the performance of HTS synchronous motors, the variation of output power characteristics according to the variation of back electromotive force (BEMF) and inductance is analysed in electric design. Reliability of proposed design process and developed program is verified through the comparison of the results of commercial program using 3D finite element analysis (FEA) method.

Optimal Design of Superconducting Motor to Improve Power Density Using 3D EMCN and Response Surface Methodology

This paper proposes an effective design process for 1 MW HTS superconducting motor by using 3-dimensional equivalent magnetic circuit network method (3D EMCN) and response surface methodology (RSM). During the process, 3D EMCN is used with a simplified 3D analysis model to get electric parameters in short time. RSM is used for the motor optimal design to improve power density. The usefulness of this method is verified through the comparison of the performances of the optimal geometry and those of the initial geometry

Comparison between three-dimensional (3D) equivalent magnetic circuit network method and 3D finite element method for magnetic-field computation

In this article, in order to investigate the merits of three-dimensional (3D) equivalent magnetic circuit network (EMCN) method, a 3D standard benchmark model proposed by the Institute of Electrical Engineers of Japan is analyzed. We also examine the accuracy of analysis results, the computer storage, and the computation time through the systematical comparison between 3D EMCN method and 3D finite element method based on hexahedral edge element. The incomplete Cholesky conjugate gradient method was selected for the solver. From the results, we can confirm the usefulness of 3D EMCN method.

Development of transverse flux linear motor with permanent-magnet excitation for direct drive applications

This paper presents the development of a transverse flux linear motor (TFLM) with permanent-magnet excitation for Stocker system, which is used for transferring glasses in the liquid crystal display industry. Magnetic field is analyzed by three-dimensional equivalent magnetic circuit network method and two-dimensional finite-element analysis is used to determine the influence of the end effect of a mover on the performance of TFLM. The experimental results of a prototyped motor are in good agreement with the analysis ones.

Multiobjective Design Optimization of Brushless Permanent Magnet Motor Using 3D Equivalent Magnetic Circuit Network Method

In this paper, we discuss multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network (EMCN) method. In the multiobjective optimization (MO) problem, we choose the decrease of cogging torque and the increase of torque as objectives. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are also selected for the design variables respectively. From the results, our approach method enabled us to efficiently obtain diverse Pareto optimal (PO) solutions from the practical point of view. The experimental results are shown to confirm the validity of the optimization results.

Performance analysis of a brushless dc motor due to magnetization distribution in a continuous ring magnet

This paper represents the force performance of a brushless dc motor with a continuous ring-type permanent magnet (PM), considering its magnetization patterns: trapezoidal, trapezoidal with dead zone, and unbalanced trapezoidal magnetization with dead zone. The radial force density in PM motor causes vibration, because vibration is induced the traveling force from the rotating PM acting on the stator. Magnetization distribution of the PM as well as the shape of the teeth determines the distribution of force density. In particular, the distribution has a three-dimensional (3-D) pattern because of overhang, that is, it is not uniform in axial direction. Thus, the analysis of radial force density required dynamic analysis considering the 3-D shape of the teeth and overhang. The results show that the force density as a source of vibration varies considerably depending on the overhang and magnetization distribution patterns. In addition, the validity of the developed method, coupled 3-D equivalent magnetic circuit network method, with driving circuit and motion equation, is confirmed by comparison of conventional method using 3D finite element method.

Magnetic force characteristics according to the variation of asymmetric overhang ratio in brushless direct current motor

As usual, brushless dc motor (BLDCM) has the overhang structure of which permanent magnet (PM) length is longer than the stator’s stack length. Specially, in case of asymmetric overhang, we have to pay attention to the choice of suitable overhang ratio of the lower to the upper overhang length because of the effect of the ratio on the magnetic forces. In this article, the magnetic force characteristics of BLDCM with the asymmetric overhang and the cap of the rotor are analyzed. A three-dimensional equivalent magnetic circuit network (EMCN) method is used for the efficient analysis of the magnetic field. The magnetic forces and torque are calculated by Maxwell’s stress tensor. The variation of magnetic force characteristics is also analyzed according to the overhang ratio. From the results, when the overhang ratio is 0.38, the axial magnetic force characteristic could be improved remarkably. The validity of the analysis results is also clarified by comparison between calculated results and measured ones.

Overhang effect analysis of brushless DC motor by 3-D equivalent magnetic circuit network method

This paper investigates the permanent magnet overhang effect in brushless dc motor. The characteristics are analyzed according to the variation of symmetric overhang length and asymmetric overhang ratio. A three-dimensional equivalent magnetic circuit network (EMCN) method is used for the accurate and efficient analysis. From the results, it is quantitatively verified that the increase of overhang length enhances the linkage fluxes of the stator and the asymmetric overhang ratio has a large effect on the axial magnetic force.

Analysis of hybrid stepping motor using 3D equivalent magnetic circuit network method based on trapezoidal element

The permanent magnet in a hybrid stepping motor (HSM) is magnetized in the axial direction. Accordingly, 2D analysis methods such as the 2D finite element method cannot guarantee accurate analysis. In this article, the characteristics of HSM are analyzed using the 3D equivalent magnetic circuit network method (3D EMCNM). The 3D EMCNM supplements the magnetic equivalent circuit by a numerical technique using distributed magnetic circuit parameters. Formerly, the 3D EMCNM based on the hexahedron element or the fan shaped element has usually been applied for linear motor analysis or rotary machine analysis. However, the use of these elements carries a serious permeance calculation error in complex shaped machinery such as a HSM. Therefore, to overcome this weakness, a new trapezoidal element is used.

3-D time-stepping analysis of induction motor by new equivalent magnetic circuit network method

A new time-stepping 3-D analysis method for analyzing induction motors is proposed. The method can analyze induction motor with faster computation time and less memory requirement than conventional numerical methods by using only scalar potential. The analysis model is divided into hexahedral elements and then an equivalent magnetic network is constructed by connecting the node of each element center. Also, the MMF by induced current combines passive source into the network. From comparisons between the results of analysis and experiments, it is verified that the proposed method can estimate the torque, harmonic field, etc. versus time with good accuracy.