Equivalent Magnetic Circuit Analysis Research Articles

Research on Braking Characteristics of Hybrid Excitation Rotary Eddy Current Retarder

According to the different excitation methods, automotive eddy current retarders (ECRs) can be divided into electrically excited retarders (EERs) and permanent magnet excited retarders (PMERs), and EERs and PMERs have certain complementarity in control and braking characteristics. Therefore, based on literature research, this article proposes a hybrid excitation rotary electromagnetic retarder (HERER) and conducts numerical simulation analysis and experimental research on the braking performance of the HERER. Firstly, the structure and working principle of the HERER are introduced. Secondly, based on the principles of electromagnetics, an equivalent magnetic circuit analysis model of the HERER is established. Then, a finite element analysis model of the HERER is established using Jmag 14 electromagnetic simulation software, and the braking performance of the HERER under different current and speed conditions is studied. Finally, bench tests are conducted on the air loss torque and eddy current braking performance of the HERER. The effectiveness of the finite element analysis model and equivalent magnetic circuit model of the HERER is verified.

Electromagnetic analysis of permanent magnet-assisted synchronous reluctance motor based on magnetic equivalent circuit

As rare-earth permanent magnet prices continue to fluctuate, interest in non-rare-earth permanent magnet-assisted synchronous reluctance motors (PMa-SynRMs) is increasing. However, non-rare-earth PMa-SynRMs have a multi-layer structure with interior permanent magnets to compensate for the low magnetic fields. Therefore, the rotor has several design parameters, and electromagnetic analysis is time-consuming. To overcome these challenges, magnetic equivalent circuit analysis was used to perform fast electromagnetic analysis of non-rare-earth PMa-SynRMs. In addition, the validity of the proposed method was confirmed through a comparison of the obtained results with those of finite element analysis.

Design of soft-magnetic shield in electromagnetic tomography

In the electromagnetic tomography system, the soft-magnetic shield is employed to avoid external interference at low frequency. However, the influence of the soft-magnetic shield on the measurement lacks theoretical exploration, and the design of the soft-magnetic shield is arbitrary. To solve this problem, the effect of different thicknesses and locations of the soft-magnetic shield on the measurement is compared by numerical simulation. It is observed that the soft-magnetic shield not only enhances the boundary measurement data and sensitivity but also improves the quality and stability of the reconstructed images. The smaller the distance between the soft-magnetic shield and the pipe, or the bigger the thickness of the soft-magnetic shield, the better the improvement. The physical mechanism of the above results is explicated by the equivalent magnetic circuit analysis method. Based on the above investigation, the optimal structure of the soft-magnetic shield is designed, and it is verified by experiments.

Electromagnetic Design and Analysis of Inertial Mass Linear Actuator for Active Vibration Isolation System

Underwater radiated noise from anthropogenic structures must be reduced to protect the marine environment. Active vibration isolation that can reduce noise generated from vibration sources by providing counteracting forces can solve this issue. This paper presents a 120 N class electromagnetic inertial mass linear actuator for an active vibration control system in a large ship. The proposed actuator is operated based on the Lorentz force, also known as electromagnetic force. To achieve a high thrust force to weight ratio, a permanent magnet with outer radial magnetization is used. In order to design and analyze the proposed model, a simple magnetic equivalent circuit analysis was first conducted to achieve an appropriate force, and its value was compared and verified with the magnetostatic finite element method. The dynamic characteristics of the actuator were then evaluated, and the performance was analyzed at various operating frequency points. The bobbin housing supporting the coil causes an eddy current loss due to materials with electrical conductivity. As a result, the damping force is generated by the reduction in magnetic flux, and the control force tends to decrease.

Performance evaluation of a new modular split‐tooth permanent magnet‐assisted switched reluctance motor

AbstractThis study elaborates upon a new modular split‐tooth permanent magnet‐assisted switched reluctance motor (MSTPM‐SRM). In the proposed topology, the stator comprises six modular E‐cores in which the middle poles are split into two teeth. Two permanent magnets (PMs) are placed between each module's middle and side poles. Primarily, the proposed topology is introduced. Next, the principle of operation of the proposed topology are elucidated, and the magnetic equivalent circuit analysis is adopted in order to validate the operational basics. It is proved that the embedded PMs significantly increase the air‐gap's flux density and adjusts the poles' flux density. The flux density distributions, static, and steady‐state characteristics of the proposed MSTPM‐SRM motor and its PMless counterpart are extracted by utilising 2‐D finite element analysis. It is illustrated that the average torque of the proposed MSTPM‐SRM is dramatically increased compared to its PMless counterpart, especially at high excitation currents. Furthermore, the cogging torque analysis is done and it is shown that the proposed structure has approximately zero cogging torque. Finally, a prototyping version of the proposed motor is fabricated, and the experimental results are elicited. It is shown that the experimental results endorse the simulation results.

Development of a Dual-Input Magnetic Gear Train for the Transmission System of Small-Scale Wind Turbines

Magnetic gear mechanisms have advanced to have a promising future in transmission technology. Previous research indicates that magnetic gear mechanisms might replace mechanical gear mechanisms in some applications. Small-scale wind turbines (SWT) with counter-rotating rotors that were initially fitted by bevel gears are proposed to be replaced by a coaxial magnetic gear train (CMGT). The CMGT is intended for use as a speed multiplier in order to obtain maximum power at low wind speeds, due to its beneficial transmission of power without physical contact. The primary objective of this study is to build a dual-input CMGT that will be employed in the transmission system of small-scale counter-rotating wind turbines. A dual-input CMGT is built through the analytical modeling of an equivalent magnetic circuit (EMC), which aims to predict the magnetic flux density in the air-gaps of CMGT. Several models within design constraints were compared to obtain the optimum design parameters of the preliminary CMGT design resulting from an EMC analysis. The optimized critical design parameters were then selected and analyzed using finite-element analysis (FEA) to depict the performance of the proposed SWT design. According to the findings, the developed design can generate an inner air-gap flux density of 0.8314 T and an outer air-gap flux density of 1.0200 T. The model likewise produces promising simulation results with an output transmitted torque in the inner rotor (output link) of 8.7 Nm, 56.9 Nm in the outer rotor, and 48.0 Nm in the carrier with pole-pieces. Thus, this design can generate higher torque than a bevel-geared wind turbine. The speed characteristics are also compromised in order to raise the generator’s rotating speed to generate more power. Finally, this study demonstrates the performance and embodiment design of the proposed SWT using CMGT.

Estimation of Solid Fraction Based on Equivalent Magnetic Circuit in TMR-Based Electromagnetic Tomography

For the gas-liquid-solid fluidized beds with magnetic catalyst, the solid fraction can be estimated through the reconstructed permeability distribution using the electromagnetic tomography (EMT) based on the tunneling magneto resistance (TMR) sensor. Considering that the existence of mixed phase and obscure phase interface leads to the inaccurate estimation of phase fraction, a new approach to estimating the solid fraction is proposed. Firstly, the equivalent magnetic circuit analysis method is introduced to abstract the magnetic field distribution, and the relationship between the boundary measurement data and the equivalent permeability of the cross-section is derived. Then, the effective medium model is employed to estimate the solid fraction of the cross-section based on the equivalent permeability. The solid fraction estimation method based on the above proposed method is more accurate than that based on the gray level of reconstructed images, especially when the permeability distribution is complex. When the true solid fraction is in the range of 0%-100%, the average of the absolute error of simulation and experiment is 2.5% and 4.8%, respectively.

Structure and Suspension Force Analysis of Six-Pole Five Degrees of Freedom AC Hybrid Magnetic Bearing

A novel six-pole five degrees of freedom (5-DOF) ac hybrid magnetic bearing (HMB) is put forward in this article, which can obtain large suspension force density, high critical speed, and reduce the nonlinearity of radial suspension force. First, the structure and suspension principle are introduced in detail and then the mathematical models of the radial and axial suspension force are derived based on the equivalent magnetic circuit analysis. Second, the main parameters are designed according to the given maximum radial and axial bearing capacities. Finally, the prototype of the six-pole 5-DOF ac HMB is established by the 3-D finite-element analysis software Magnet. Moreover, the electromagnetic analysis is carried out to verify the rationality of the magnetic circuits and suspension mechanism. Furthermore, the force-current relationships are calculated. The research results have shown that the proposed six-pole 5-DOF ac HMB has reasonable structure and good suspension performances.

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

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

Design and performance analysis of permanent magnet linear synchronous motor

In order to effectively control the vibration transmitted from the ground to the precision equipment, permanent magnet linear synchronous motor (PMLSM) can be effectively applied in the active vibration absorber systems due to its good characteristics. The design of a PMLSM is very important because of the special requirements of the damping system on the response speed, working temperature, working bandwidth and installation size of the PMLSM. In this paper, the multi-objective design problem of the PMLSM in vibration damping system is proposed. Based on the equivalent magnetic circuit analysis of the PML SM’s air gap magnetic field, the performance and design of the PMLSM are effectively analyzed in combination with the design objectives. The design and performance of the prototype meet the design requirements.

Basic Characteristics and Design of a Novel Hybrid Magnetic Bearing for Wind Turbines

This paper proposes a five-degree-of-freedom (5-DOF) hybrid magnetic bearing (HMB) for direct-drive wind turbines, which can realize suspension in the 4-DOF radial and 1-DOF axial directions. Only two sets of radial control windings are employed in the proposed HMB because only one set of radial control windings can achieve the 2-DOF suspension in the radial direction. Unlike the traditional active thrust magnetic bearings, this paper uses a cylindrical rotor core without a large thrust disc in the novel HMB. The numbers of the controller, power amplifier and system volume can be reduced in the magnetic suspension system. This paper also presents the structure and basic characteristics of the proposed magnetic bearing. A precision equivalent magnetic circuit analysis of the permanent magnet ring and control magnetic field is conducted in this study, in consideration of the non-uniform distribution of magnetic density. Accordingly, the mathematical models, including the suspension force expression, are derived based on the accurate equivalent magnetic circuit. The basic principle of the structure parameter design is presented, based on the given key parameters. The accuracy of the analytical method is further validated by 3D finite element analysis.

Magnetic circuit model and finite‐element analysis of a modular switched reluctance machine with E‐core stators and multi‐layer common rotors

This study presents a novel switched reluctance machine (SRM) with modular E-core stators and multi-layer common rotors for high reliability applications. The stator is composed of six independent modular E-cores with the windings wound around the yoke of the E-cores. The rotor consists of three magnetically independent common rotors which are place in the same shaft without any angular shift. The equivalent magnetic circuit (EMC) models of this new SRM at the aligned and unaligned positions are described. To evaluate the motor performance, two types of analysis, namely, approximate simplified two-dimensional (2D) model and 3D model finite-element analysis (FEA) have been utilised. The 2D FEA static and dynamic results are compared with 3D FEA results. Furthermore, comparisons between the novel modular SRM and a conventional 6/4 SRM are made. Finally, a prototype of this modular SRM has been fabricated and tested in the laboratory. Comparison between FEA and EMC analysis for flux linkage are made and compared with measured characteristics. The simulated and measured phase currents and average torque are also presented and compared to verify the analytical and simulation results.

Experiment and Torque Modeling of Double-Excited, Two-Degree-of-Freedom Motor based on Magnetic Equivalent Circuit Analysis

This paper presents the magnetic equivalent circuit analysis of a double-excited, twodegree-of-freedom (DOF) motor. The double-excited, 2-DOF motor is a laminated structure, making it easy to manufacture and giving it simple operating principles. We explain the structure of the 2-DOF motor and analyze the static characteristics using a magnetic equivalent circuit (MEC) to reduce analysis time. The feasibility of MEC analysis was confirmed by experimental results of the tilting, panning motion. We also confirmed the occurrence of holding torque in every motion.

Lumped parameter modeling and analysis of hybrid magnet engine valve actuator

The hybrid magnet engine valve actuator (HMEVA) composed of two types of magnets (permanent magnet and electromagnet) and two balanced springs is a promising tool for implementing innovative engine management strategies for variable valve timing. Finite Element Method (FEM), a favored actuator design tool due to its high accuracy, was utilized to analyze the electromagnetic actuator, but it consumes a lot of time especially in computation iterations for optimization. Accordingly, the magnetic equivalent circuit analysis can be an alternative tool to FEM because of its computation iteration capability with fair accuracy. In this paper, an equivalent magnetic circuit model of an HMEVA is developed considering the reluctances, external magnetic forces and so on, and the simulation results are presented. In addition, the result of lumped parameter analysis (LA) is compared with those obtained from finite element analysis for verification.

평판형 전자기 엑츄에이터의 집중매개변수 모델링 및 해석

평판형 전자기 엑츄에이터는 이동코일과 가이드 사이의 마찰이 없기 때문에 초정밀 제품에 널리 사용된다. 전자기 엑츄에이터의 성능 검증에 가장 많이 사용되는 방법 중 한 가지는 유한요소해석 방법이다. 하지만 유한요소해석 방법은 해석 시간이 많이든다는 단점이 있다. 유한요소해석 방법의 대안으로 계산시간은 짧지만 높은 정확도의 해석 결과를 도출해 낼 수 있는 집중매개 변수모델 해석방법이 많이 사용되고 있다. 본 논문에서는 평판형 전자기 엑츄에이터의 집중매개변수 모델링을 생성하고 시뮬레이션을 통해 성능을 검증하고 그 결과를 유한요소해석 결과와 비교해 본다. The flat coil actuator is widely used to make high precision products because it has no friction between the moving coil and the guide. Finite Element Method, a favored actuator design tool due to its high accuracy, was utilized to analyze the electromagnetic actuator, but it consumes a lot of time especially in computation iterations for optimization. Accordingly, the magnetic equivalent circuit analysis can be an alternative tool to FEM because of its computation iteration capability with fair accuracy. In this paper, lumped parameter model and the simulation results are presented. In addition, the result of lumped parameter analysis is compared with those obtained from finite element analysis for verification.

Novel Two-Phase Switched Reluctance Machine Using Common-Pole E-Core Structure: Concept, Analysis, and Experimental Verification

A novel two-phase switched reluctance machine (SRM) with a stator comprised of E-core structure having minimum stator core iron is proposed. The E-core stator has three poles with two poles at the ends having windings and with the center pole containing no copper windings. The center stator pole in the E-core is shared by both phases during operation. The air gap around the common pole has constant and minimum reluctance irrespective of rotor position by its unique design and the two remaining stator poles at the ends experience variable reluctance with respect to rotor position. The stator is constructed with two independent and physically separate E- cores and the rotor is comprised of ten poles. Other pole combinations are possible. Phase excitation in the novel SRM gives short flux paths, hence reducing the magnetomotive force (MMF) required to drive the machine resulting in significant reduction of copper wire and core-losses compared to existing two-phase SRMs with flux-paths that traverse the entire stator back iron. The concept and principle of operation of this novel SRM and its comparison and contrast to existing two-phase SRMs are detailed in this paper. Comparison between finite element simulations and magnetic equivalent circuit analysis for inductance are made and compared to experimentally measured characteristics. Furthermore, a comparison between a conventional two-phase SRM and the novel SRM is be made in terms of its weight and output torque. Manufacturability and cost savings of the unique SRM structure are presented. It is shown that E-core SRM using common-pole SRM has 50% less iron in the magnetic path compared to the conventional two- phase SRM.

Detection of gas pipe wall thickness based on electromagnetic flux leakage

Based on electromagnetic flux leakage (EMFL), a nondestructive testing (NDT) technique for the detection of gas pipe wall thickness is presented, and its principle and feasibility is evaluated by means of equivalent magnetic circuit analysis and finite element analysis. An online NDT device adopting this technique is developed, and its structure and working principle are introduced in detail. This device is composed of a detector array with 32 pipe wall thickness sensors that employ a Hall element as the element for sensing the magnetic flux density, and it can be adapted to pipe diameters from O400mm to O650 mm. On the basis of the experimental investigation for this device, the influences of some factors on thickness measurement, namely the excitation current, excitation coil turns, gap distance, concentrator of the magnetic field, magnetization time, and number of sensors in the detector array, are revealed and the optimal excitation voltage for the sensors of the detector array is selected. The measuring calibration is given to establish the relationship between the pipe wall thickness and the output voltage of the sensors. The results show that the proposed EMFL for measuring the wall thickness of ferromagnetic pipe is feasible, the technical parameters of the sensor are important for improvement of measurement precision and resolution, and the developed device has precision, resolution, and a linear output curve. Carried by the developed gas pipeline inspection robot through a universal joint, this NDT device can move inside the gas pipeline and monitor the state of the pipe wall.

Static Properties of Magnetic Force Control Device using Lamination of Magnetostrictive and Piezoelectric Materials

A magnetic force control device using laminate composite of magnetostrictive and piezoelectric materials is proposed. This magnetic force control is based on the inverse magnetostrictive effect, whereby the variation of the magnetization in the magnetostrictive material changed with an applied voltage on the piezoelectric material is converted to that of a magnetic force via magnetic circuit. Due to the capacitive property of the piezoelectric material, the device requires little electric energy to maintain constant force. Furthermore, the device is easy to assemble compared with our proposing conventional device. In this paper, the static characteristics, voltage vs. magnetic force, energy conversion ratio and power consumption are investigated. The calculation of the magnetic force combining a FEM and equivalent magnetic circuit analysis is verified.

Comparison of lumped parameter and finite element magnetic modeling in a brushless DC motor

The FEM is a favored motor design tool for its high accuracy. Magnetic equivalent circuit analysis, an alternative to FEM, is becoming popular for its fair accuracy and quick repetition of computation. An equivalent circuit model of a brushless DC motor is developed and its ability to accurately predict various motor performance parameters is assessed.