Eddy-Current Loss Analysis of Noncontact Magnetic Device With Permanent Magnets Based on Analytical Field Calculations

Min, Kyoung-Chul,Choi, Jang-Young,Kim, Jeong-Man,Cho, Han-Wook,Jang, Seok-Myoeng IEEE 2015 IEEE transactions on magnetics Vol.51 No.11

<P>This paper reports on the analysis of eddy-current loss of a magnetic coupling (MC) that uses a Halbach array permanent magnet (PM). A MC is a kind of noncontact magnetic device (NCMD). When the conductive materials of NCMDs are exposed to time-varying magnetic fields, eddy currents are induced in the conductive materials, leading to losses. An analysis of the eddy-current loss is therefore required, and for MCs, the analysis of eddy-current loss is particularly more important. We obtain the magnetic field solutions of the Halbach magnetized PM based on the magnetic vector potential and 2-D polar-coordinate system. In addition, using the derived magnetic field solutions, we derive analytical solutions for eddy-current loss using the equivalent electrical resistance that is calculated from the magnet volume and conductivity. A 2-D finite-element analysis is employed to confirm the validity of the analytical results of the eddy-current density and eddy-current loss. Finally, we investigate the influence of the number of Halbach segments on the eddy-current loss induced on the MC.</P>

Numerical and Experimental Study of Magneto-eddy Current Effects on Self-piercing Riveting (SPR) for Joining Dissimilar Materials

J. Kim(김정섭),C. B. Lee(이차범) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

In this paper, the magneto-eddy currents on SPR have been numerically simulated and experimentally investigated for non-destructive testing of the SPR. The magnetic field- and electromagnetic field-driven magnetic force distribution was characterized with respect to the measurement target formation. First, finite element analysis (FEA) was performed to characterize the magneto-eddy current effects by focusing on the correlation between permanent magnet-induced attraction force and eddy current. Second, based on the FEA, a magneto-eddy current sensor (MECS) to measure the magneto-eddy current effects on SPR was designed and instrumented. The MECS combining the magnetic force sensor and the eddy current sensor non-destructively enables measuring the magneto-eddy current of SPR configuration like a combination of carbon fiber reinforced plastic (CFRP) and aluminum (Al). Finally, the 3-axis scanning experiments were performed to validate performing MECS by combining the magnetic testing for the steel rivet and the eddy current testing for the Al plate. As a result, the magneto-eddy current effects can be used to defect the defects of SPR available for non-destructive SPR quality assessments.

An eddy current effect on the response time of a magnetorheological damper: Analysis and experimental validation

Yoon, Dal-Seong,Park, Yu-Jin,Choi, Seung-Bok Elsevier 2019 Mechanical systems and signal processing Vol.127 No.-

<P><B>Abstract</B></P> <P>This work proposes a new magnetorheological (MR) damper which can produce sufficient damping force within a few millisecond. Firstly, damping force mechanisms of MR damper are analyzed by deriving several equations representing the flow motion. Then, the eddy current analysis of several different core materials is undertaken since it most significantly influences to the time delay of MR damper. After analyzing several candidates of the magnetic core material, the soft magnetic composite (SMC) is selected which has relatively high electric resistivity. In addition, the inner surface of the housing is machined to have many grooves around the housing to reduce the eddy current magnitude. After confirming that the proposed MR damper causes a very small eddy current distribution, two MR dampers are designed and manufactured by considering the order of the influence level of the factors determined on the basis of Taguchi method. The field-dependent damping force to the step input current is then measured in time domain and the response time of MR damper is calculated. It is shown through experimental tests that very fast response time of MR damper can be achieved by reducing the eddy current around the magnetic field zone.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A fast responsive MR damper is proposed by analyzing the eddy current distribution. </LI> <LI> Grooves are carved on inner surface of the housing for reduction of the eddy current. </LI> <LI> MR damper response become faster with eddy current reducing design & high resistors. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

인공위성 고도계 자료와 해색 위성 자료 기반의 동해 중규모 소용돌이 탐지 비교

박지은,박경애,PARK, JI-EUN,PARK, KYUNG-AE 한국해양학회 2019 바다 Vol.24 No.2

인공위성 자료를 활용한 중규모 소용돌이 탐지에는 해수면온도, 식물플랑크톤 클로로필-a 색소 농도, 해수면고도 등 다양한 해양 변수를 활용할 수 있다. 각 위성 해양 자료는 시 공간 해상도, 관측 방식 및 자료 처리 과정이 상이하기 때문에, 동일한 소용돌이에 대해서도 다른 탐지 결과를 유도할 수 있어, 인공위성 자료를 활용한 소용돌이 탐지에 대한 기초 연구가 필요하다. 본 연구에서는 해색 위성 자료, 위성 고도계 해수면고도 자료, 적외선 해수면온도 자료를 활용하여 동해 중규모 소용돌이를 탐지하고 그 결과를 상호 비교하였다. 연속된 해색 위성 클로로필-a 농도 영상으로부터 최대 상호 상관 계수를 통하여 산출한 표층 해류장과, 위성 고도계의 해수면고도 영상 자료로부터 산출한 지형류를 활용하여 동해 중규모 소용돌이를 탐지하였다. 소용돌이 탐지 결과를 상호 비교하기 위하여 1) 해색 영상과 고도계 영상이 동시에 소용돌이를 탐지한 경우, 2) 해색 영상과 해수면온도 영상에는 존재하나 고도계 자료는 탐지하지 못한 경우, 3) 해색 영상과 해수면온도 영상에는 소용돌이가 존재하지 않으나 고도계 자료에서는 존재하는 경우 등 세 가지 사례를 선택하였다. 이와 같은 세 가지 사례를 통하여 동해 중규모 소용돌이 탐지 시 인공위성 고도계 자료의 문제점 제기와 더불어, 해색 위성 자료와 적외선 해수면온도 자료의 한계점을 제시하였다. 또한 해양 현상과 인공위성 관측 원리에 대한 깊이 있는 이해를 기반으로 소용돌이 탐지 및 관련 연구가 진행되어야 함을 강조하였다. Detection of mesoscale oceanic eddies using satellite data can utilize various ocean parameters such as sea surface temperature (SST), chlorophyll-a pigment concentration in phytoplankton, and sea level altimetry measurements. Observation methods vary for each satellite dataset, as it is obtained using different temporal and spatial resolution, and optimized data processing. Different detection results can be derived for the same oceanic eddies; therefore, fundamental research on eddy detection using satellite data is required. In this study, we used ocean color satellite data, sea level altimetry data, and infrared SST data to detect mesoscale eddies in the East Sea and compared results from different detection methods. The sea surface current field derived from the consecutive ocean color chlorophyll-a concentration images using the maximum cross correlation coefficient and the geostrophic current field obtained from the sea level altimetry data were used to detect the mesoscale eddies in the East Sea. In order to compare the eddy detection from satellite data, the results were divided into three cases as follows: 1) the eddy was detected in both the ocean color and altimeter images simultaneously; 2) the eddy was detected from ocean color and SST images, but no eddy was detected in the altimeter data; 3) the eddy was not detected in ocean color image, while the altimeter data detected the eddy. Through these three cases, we described the difficulties with satellite altimetry data and the limitations of ocean color and infrared SST data for eddy detection. It was also emphasized that study on eddy detection and related research required an in-depth understanding of the mesoscale oceanic phenomenon and the principles of satellite observation.

한국 서남해 압해도 주변 다도해역의 조류 및 조석잔차류 분포

추효상,김동선 해양환경안전학회 2018 해양환경안전학회지 Vol.24 No.2

In order to understand the flow of currents around Aphae Island and the surrounding Archipelago, the numerical model experiments on tidal currents and tide-induced residual currents were carried out. Dominant semidiurnal tidal currents have a reversing form and flow along the narrow channels of the archipelago. During periods of flood, currents flow from the west of Hwawon Peninsula to the archipelago to the northwest together with the currents flowing from the channels at Palgeum Island to Amtae Island and Amtae Island to Jeung Island. Ebb currents flow from the northwest archipelago to the channel of Amtae Island and Jeung Island as well as Amtae Island to Palgeum Island, further flowing south between Palgeum Island and Hwawon Peninsula. Flood currents are separated from east and west at the southern coast of Aphae Island, but flow south from both the west and east of Aphae Island to the channel found between Palgeum Island and Hwawon Peninsula at ebb. Flow speed is high between Amtae Island and Aphae Island where the flows meet and join. Lee wakes or topographical eddies are formed around the islands due to the high speed of the currents flowing along the narrow channel in the archipelago, manifesting as a tide-induced residual current. A weak cyclonic wake and anti-cyclonic eddy both exist at the west and northwestern coast of Aphae Island individually. The speed of the tide-induced residual current become slow on account of the wide littoral zone at exists around Aphae Island. 수치모델실험을 사용하여 한국 서남해 압해도 주변 해역의 조류 및 조석잔차류 분포를 파악하였다. 조류는 대체로 반 일주조가 탁월하며, 조류 주방향은 압해도 주변 다도해역이 좁은 협수로인 관계로 대부분 수로를 따라 형성되었다. 조류타원 형태는 주변수심 및 인근에 산재한 섬 주위 해저지형의 영향으로 대부분 직선에 가까운 왕복성이었으나, 매화도~증도 사이 기점도, 화도, 당사도 주위에 약한 회전성 조류타원 형태였다. 창조류는 화원반도 서쪽 연안을 따라 팔금도~암태도, 암태도~증도 수로에서 북동류한 조류와 함께 압해도 북서쪽 다도해로 빠지고, 낙조류는 반대로 북서 다도해의 협수로를 따라 암태도~증도, 암태도~팔금도를 통과하고 암태도~증도에서의 조류는 팔금도~화원반도 서쪽 연안을 따라 남류했다. 압해도 연안은 창조시 북류한 흐름이 해안에서 동서로 분류되어 압해도 서쪽과 동쪽을 따라 흐르고 낙조시는 조간대 만곡부에서 남류한 흐름과 섬 서쪽과 동쪽에서 남~남동류한 흐름이 팔금도~화원반도 사이로 흘렀다. 조류유속이 강한 곳은 암태도~압해도 사이 합류역이었다. 조석잔차류는 다도해 협수로의 빠른 유속으로 섬 주변 흐름 하류역에 후류와 또는 지형성와류가 형성되었다. 압해도 서쪽에 약한 반시계방향 와류와 압해도 북서 만곡부에 시계방향 환류가 존재했다. 북쪽 협수로를 제외한 압해도 연안은 조간대가 발달되어 조석잔차류 유속이 미약하였다.

결함과 형상변화가 혼재하는 전도성 물체의 와전류 신호의 분석

권찬울,김종민,박재하,김학준,송성진,나승우,황우채,권성덕 한국물리학회 2017 새물리 Vol.67 No.3

Eddy-current testing, which is one of the nondestructive evaluation techniques, is widely used to detect surface defects and evaluate the properties of conducting materials. The basic principle of eddy-current testing is to measure the impedance change induced in a coil by surface defects. However, the majority of products used in the industrial field have uneven surfaces due to various factors. If an exact eddy-current inspection technique is to be applied, the signals generated by defects and by shape changes must be separated and analyzed. Therefore, in this study, we tried to separate the signal caused by defects from the signal due to shape change in a signal where the defects and the shape change were mixed. As a result of simulations and experiments on changes in the resistance and the reactance, the differential signal due only to the shape change was confirmed. Because of this, the defect signal could be distinguished the signal containing the defect and the shape-change signals. Then, when we accumulate data for various shape-change signals, this will be very useful tool for separating only the defect signals from the mixed signals. 표면 결함 검출 및 전도성 피검사체의 물성평가를 위해 비파괴평가 기법의 하나인 와전류 탐상이 널리 사용되고 있다. 와전류 탐상은 피검사체의 표면결함에 의한 유도 코일의 임피던스 변화를 측정하는 기법이다. 하지만, 산업현장에서 사용 중인 대다수의 제품은 여러 가지 요인들로 인해 고르지 못한 표면을 가지고 있다. 정확한 와전류 탐상 기법을 적용하기 위해서는, 결함에 의해 발생한 신호와 형상변화 때문에 발생한 신호를 적절하게 분리, 분석할 필요가 있다. 이에 본 연구에서는 결함과 형상변화가 혼재하는 신호에서 형상변화에 의한 신호만을 분리하여, 결함만에 의한 신호의 분리를 시도하였다. 시뮬레이션 및 실험 결과, 형상변화 만에 의한 차등신호를 확인 하였고, 이로부터 결함신호와 결함과 형상변화가 혼재하는 신호를 구별할 수 있었다. 이후 다양한 형상변화 신호에 대한 데이터를 축적한다면, 혼재신호로부터 결함신호만을 분리하는 매우 유용한 도구가 될 것으로 판단된다.

Analytical Solution of Magnetic Field in Permanent-Magnet Eddy-Current Couplings by Considering the Effects of Slots and Iron-Core Protrusions

Xin Dai,Qinghua Liang,Chao Ren,Jiayong Cao,Jinqiu Mo,Shigang Wang 한국자기학회 2015 Journal of Magnetics Vol.20 No.3

In this study, we propose an analytical model for studying magnetic fields in radial-flux permanent-magnet eddy-current couplings by considering the effects of slots and iron-core protrusions on the eddy currents. We focus on the analytical prediction of the air-gap field by considering the influence of eddy currents induced in conducting bars. In the proposed model, the permanent magnet region is treated as the source of a timevarying magnetic field and the moving-conductor eddy current problem is solved based on the resolution of time-harmonic Helmholtz equations. The spatial harmonics in the air gap and in slots, as well as the time harmonics are all considered in the analytical calculation. Based on the proposed field model, the electromagnetic torque is computed by using the Maxwell stress tensor method. Nonlinear finite element analysis is performed to validate the analytical model. The proposed model can be used for permanent-magnet eddy-current couplings with any slot?pole combination.

해석적 방법을 이용한 슬롯리스 양측식 코어드 타입 영구자석 발전기의 와전류 손실 해석

장강현(Gang-Hyeon Jang),정경훈(Kyoung-Hun Jung),홍기용(Keyyong Hong),김경환(Kyong-Hwan Kim),최장영(Jang-Young Choi) 대한전기학회 2016 전기학회논문지 Vol.65 No.10

This paper deals with eddy current loss analysis of Slotless Double sided Cored type permanent magnet linear generator by using analytical method, space harmonic method. In order to calculate eddy current, this paper derives analytical solution by the Maxwell equation, magnetic vector potential, Faraday’s law and a two-dimensional(2-D) cartesian coordinate system. First, we derived the armature reaction field distribution produced by armature wingding current. Second, by using derived armature reaction field solution, the analytical solution for eddy current density distribution are also obtained. Finally, the analytical solution for eddy current loss induced in permanent magnets(PMs) are derived by using equivalent, electrical resistance calculated from PMs volume and eddy current density distribution solution. The analytical result from space harmonic method are validated extensively by comparing with finite element method(FEM).

Analysis of Anisotropic Characteristic in Fiber Reinforced Polymer for the Knee Brace Using the Eddy Current Inspection

김철웅(Cheol-Woong Kim),박천웅(Cheon-Woong Park),신용훈(Yong-Hoon Shin),서해용(Hae-Young Seo),이호상(Ho-Sang Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

The development of new material systems like Carbon Fiber Reinforced Polymer (CFRP) places ever higher demands on the techniques for non-destructive material characterisation. Image-producing eddy current methods also need to satisfy these demands. Eddy-current imaging of FRP is based on the anisotropic electrical properties of the material investigated. Significant differences in conductivity between carbon fibres, polymer matrix and integrated functional components can be found. The availability of high-resolution sensors enables access to the local distribution of the electromagnetic properties. The static and dynamic procedures for isolating influential characteristics, already in use in eddy-current technology, can now be supplemented by topographical images. The precondition for a successful implementation of the eddy-current procedure is a deeper understanding of the image-generating process which allows correct interpretation of the images obtained.

Eddy Current Damping System의 진동 저감 특성 평가

안태원 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.1

Generally, vibration absorber systems are composed of spring-mass systems to reduce the vibration of a structure, and there are also methods to simply increase damping to achieve a damping effect across a wide frequency band. One similar method is to use a mechanism in which the eddy current is converted into a mechanical damping effect. When an eddy current is generated by electromotive force due to magnetic flux change, the reaction force is generated by the eddy current’s circulation. In this study, the damping system using the reaction force was constructed to reduce the transmission of vibrations generating from internal fluid and the vibration reduction characteristics that are transmitted externally were analyzed. As a result, 8.2 % of the vibration reduction effect from primary excitation frequency was confirmed.