• Title/Summary/Keyword: demagnetization effect

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Effect of Magnetization Pattern on Partial Demagnetization of Rotary Electric Machines with Ferrite Magnets (페라이트 영구자석을 이용한 회전형 전기기기의 착자 형태에 따른 부분 감자의 영향)

  • Kim, Kwan-Ho;Park, Hyung-Il;You, Dae-Joon;Jang, Seok-Myeong;Choi, Jang-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.12
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    • pp.1679-1685
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    • 2015
  • This paper examines the effect of the magnetization pattern on the partial demagnetization of a permanent magnet (PM) machine that uses a ferrite magnet. Although the use of halbach-magnetized PM (HMPM) arrays in PM machines has been dramatically increasing because of their attractive features, the demagnetization characteristics of HMPM arrays have not yet been examined. In this study, two analyses of the demagnetization characteristics of HMPM arrays and parallel magnetized PMs (PMPMs) are performed, with the demagnetization characteristics being analyzed using a finite element method. According to our results, partial demagnetization occurred dramatically in the HMPM arrays. Thus, it is important to consider the vulnerability of HMPM arrays when designing PM machines.

Impact of Eccentricity and Demagnetization Faults on Magnetic Noise Generation in Brushless Permanent Magnet DC Motors

  • Rezig, Ali;Mekideche, Mohammed Rachid;Djerdir, Abdesslem
    • Journal of Electrical Engineering and Technology
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    • v.6 no.3
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    • pp.356-363
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    • 2011
  • Vibrations and noise in electrical machines are directly related to the characteristics of the radial forces on one hand, and mechanical behavior on the other [1, 4]. The characteristics of these forces depend on the air gap flux density, which is also influenced by other factors, such as stator slots and poles, saturation level, winding type, and certain faults. The aim of this work is to investigate the effect of eccentricity and demagnetization faults on electromagnetic noise generated by the external surface of Permanent Magnet Synchronous Machine [PMSM]. For this purpose, an analytical electromagnetic vibroacoustic model is developed. The results confirm the effect of eccentricity and demagnetization fault in generating some low modes radial forces.

Dynamic Analysis Algorithm of Irreversible Demagnetization of IPM-type Brushless DC Motor by Stator Turn Fault (고정자 절연파괴 고장에 의한 매입형 영구자석 BLDC 모터의 불가역 감자에 대한 동적해석 알고리즘)

  • Lee, Yoon-Seok;Kim, Kyung-Tae;Hur, Jin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.12
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    • pp.1661-1667
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    • 2013
  • This paper studies the dynamic irreversible demagnetization characteristics of an interior permanent magnet (PM) brushless DC motor with a stator turn fault. A new algorithm, which is a finite element method (FEM) combined with a line voltage equation of the motor, is developed to analyze irreversible demagnetization under dynamic and transient states and considers a stator turn fault. The input current, circulating current, magnetic distribution characteristics, and operating property of the PM, including the irreversible demagnetization in the fault state, are analyzed using this algorithm by considering the magnetic saturation effect. The feasibility of the proposed method confirmed from the analysis results is verified via an experiment. Through this fault analysis, we can accurately check the fault phenomena of a PM motor against the demagnetization fault for fault prevention.

On The Dynamics And The Demagnetization Effect Of The Amplidyne Generator With Auxiliary Feedback Compensating Winding (상태변수에 의한 회전형전자증폭기의 동특성 해석 및 감자작용효과에 관한 연구)

  • Se Hoon Chang
    • 전기의세계
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    • v.21 no.6
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    • pp.9-16
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    • 1972
  • This work intends to study the machine dynamics in the state-space approah and to formulate the operating characteristics of a namplidyne generator, with balanced control field winding and an auxiliary feedback winding for compensating purpose. In the derivation of the dynamic equation, investigations on the demagnetization effects are accentuated, based on the magnetic interlinks between windings of the machine. From the machine dynamic relation obtained, a state-variable representation of the machine dynamics is approached in the first part of this work.

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Influence of Shape Demagnetization Effect for Naval Vessel Deperming (함정의 형상 반자계 효과가 탈자에 미치는 영향)

  • Kim, Young-Hak
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.2
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    • pp.445-450
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    • 2016
  • This paper studied on the influence of naval vessel shape on vertical magnetic field after the vessel was demagnetized. The triangular shape, the rectangular shape and circular shape were adaped from vessel's structual drawings. Magneto-static FEM analysis was performed to obtain the iduced magnetic field due to earth magnetic field for those shapes. During demagnetization process, magnetic field of residual magnetization was observed. The holizontal and vertical magnetic field were calculated depending on vertical bias magnetic field through magnetc component seperation. To demagnetize naval vessel ship, demagnetizing coils shoud be wound more finely in the vow and stern of the ship than it should be in the mid-part of the ship.

Analytical Study of the Machine Dynamics of the Amplidyne Under the Demagnetization Effect (계산기에 의한 회전형전자증폭기의 동특성 및 감자작용 영향에 관한 해석적 연구)

  • Se Hoon Chang
    • 전기의세계
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    • v.22 no.1
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    • pp.9-19
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    • 1973
  • This paper is for the supplementary studies of the theoretical treaties on the machine dynamics of the amplidyne generator under the influencies of the armature reaction. The author has already shown the time-domain expression of the dynamic relations of the machine with balanced control winding, under this operating condition. In this paper, analytical and experimental studies of a test machine are intended to supplement the theories derived in the previous work, entitled "On the dynamics and the demagnetization effect of the amplidyne generator with auxiliary feedback compensating winding". FACOM 230 digital computer is incorporated for processing of a series of experimental data. The machine dynamics are then numerically analyzed with the aid of the computer. The virtual machine responses to stepwise inputs are compared with the computer output to confirm the influence of the armature reaction effect on to the machine dynamics. dynamics.

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Effective Way of Measuring $K_I$ by Means of ACPD Technique (교류전위차법을 이용한 효과적인 응력확대계수의 측정 방법)

  • Lee, Jeong-Hee
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.1
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    • pp.8-15
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    • 1999
  • In order to develop an effective way of measuring the mode I stress intensity factor, $K_I$, by the technique based on the alternating current potential drop (ACPD), the effect of the magnetic flux in the air on the change in potential drop due to load for both ferromagnetic and paramagnetic materials containing a two-dimensional surface crack was investigated. Additionally the effects of the demagnetization and the crack length on the change in potential drop were examined. In the case that the measuring system was designed to induce a large amount of electromotive force, the amount of the change in potential drop due to load was shown to increase largely Also the relationship between the change in potential drop and that in $K_I$ was indicated to be linear without any treatment and it was shown that the demagnetization had almost no effect on the change in potential drop. The change in potential drop did not depend on the crack length but on the measuring system. For the application of the ACPD technique to determine $K_I$.

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Analyses of Laser Induced Demagnetization and Remagnetization in Carbon Doped FePt Thin Films (탄소가 도핑 된 FePt 박막에서의 펨토 초 펄스 레이저에 의한 자기 소거와 회복 분석)

  • Song, Hyon-Seok;Ko, Hyun Seok;Hong, Jung-Il;Shin, Sung-Chul;Lee, Kyeong-Dong;Park, Byong-Guk
    • Journal of the Korean Magnetics Society
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    • v.25 no.2
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    • pp.39-42
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    • 2015
  • After preparing carbon-doped FePt films by dc magnetron sputtering, we observed ultrafast demagnetization and its recovery by means of a time-resolved magneto-optical Kerr effect technique. We confirm that the degree of $L1_0$ ordering is decreased and coercivity is changed, as the carbon concentration increases. All samples are demagnetized within ~5 ps after the femtosecond laser pulse heated the sample. Interestingly, ultrafast relaxation time, which indicates fast magnetization recovery, increases as the carbon concentration increases due to the low spin-orbit coupling of carbon.

Loading Effect on ACPD of a Crack in Paramagnetic Material (균열을 가진 상자성체의 교류전위차에 미치는 하중의 영향)

  • Lee, Jeong-Hee
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.1
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    • pp.1-7
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    • 1999
  • In order to determine the mode I stress intensity factor ($K_I$) by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for a paramagnetic material containing a two-dimensional surface crack was examined. The cause of the change in potential drop and the effects of the magnetic flux and the demagnetization on the change in potential drop were clarified by using the measuring systems with and without removing the magnetic flux from the circumference of the specimen. The change in potential drop was linearly decreased with increasing the tensile load and was caused by the change in conductivity near the crack tip. The reason of decreasing the change in potential drop with increasing the tensile load was that the increase of the conductivity near the crack tip due to the tensile load caused the decreases of the resistance and internal inductance of the specimen The relationship between the change in potential drop and the change in $K_I$ was not affected by demagnetization and was independent of the crack length.

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