• Steel and Composite Structures
• /
• v.19 no.3
• /
• pp.601-614
• /
• 2015

The Metal Magnetic Memory (MMM) method is a non-destructive testing method based on an analysis of the self-magnetic leakage field distribution on the surface of a component. It is used for determining the stress concentration zones or any irregularities on the surface or inside the components fabricated from ferrous-based materials. Thus, this paper presents the MMM signal behaviour due to the application of fatigue loading. A series of MMM data measurements were performed to obtain the magnetic leakage signal characteristics at the elastic, pre-crack and crack propagation regions that might be caused by residual stresses when cyclic loadings were applied onto the A283 Grade C steel specimens. It was found that the MMM method was able to detect the defects that occurred in the specimens. In addition, a justification of the Self Magnetic Flux Leakage patterns is discussed for demonstrating the effectiveness of this method in assessing the A283 Grade C steel under cyclic loadings.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.401-408
• /
• 2011

Nowadays, the development of sustainable transportation has been researched all over the world and Korea Railroad Research Institute (KRRI) is conducting a study in order to apply the sustainable Contactless Inductive Power Supply Technology to the electric railway system. But, inherent large flux leakage has limited the high power transmission because the gap of the Inductive Power Transformer(IPT) is much larger than one of the conventional transformers. In this study, a method to compensate the leakage flux and improve the power transmission by using LLC resonant inverter was proposed, incorporated in a built system, and verified by experimental work.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2013.01a
• /
• pp.257-258
• /
• 2013

본 연구에서는 피복 손상으로 주변 도전체를 통해 누전되었을 때 그 주변의 자장을 검출하여 누전 여부를 판단할 수 있는 장치개발을 하기 위하여 우선 표면 누전에 의한 전류의 흐름을 조사하고, 전류에 의한 자장을 검출하기 위해 센서를 제작한다. 코어는 요크 타입을 적용하였으며, 코일은 0.5[mm] 동선을 4,000회 감았다. 실험 환경은 전선 피복 손상에 의한 금속 표면에 누전되는 상황을 모의하였으며, 부하는 40[W], 400[W], 1,400[W]를 적용하였다. 센서는 표면에 발생되는 자장을 검출할 수 있도록 2축으로 구성하였으며, 전선 주변 및 누전된 금속 표면에서 거리 및 각도 변화에 따른 자장을 검출하였다.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1111-1112
• /
• 2011

This paper investigated application of fractional-slot concentrated-winding axial flux permanent magnet machines for wind turbines. Design criteria of cogging torque and voltage regulation was firstly proposed for this kind of application. Fractional winding has small cogging torque which is highlight for wind turbines, but slot leakage inductance would increase voltage regulation, which is an important performance index of generators. By varying slot opening, cogging torque and slot leakage inductance could be adjusted. In this paper, cogging torque and inductances were calculated by both analytical and finite element methods. Voltage regulation was studied by two-axis model under unity-power-factor load and verified by transient finite element analysis.

• Proceedings of the KIEE Conference
• /
• 2007.10c
• /
• pp.62-64
• /
• 2007

자기누설 탐상(Magnetic Flux Leakage)시스템은 비파괴 검사의 일종으로 대상 물체를 자화시켜 결함 부위에서 자기 누설량을 측정함으로써 구조물의 결함 및 부식 등을 탐지하는 시스템이다. 지하 가스배관의 결함 판정에 있어 기존의 신호처리 기법을 통한 노이즈 제거와 검출 성능 향상은 한계가 있다. 이는 후처리 단계로써 각종 노이즈를 포함하고 있기 때문이다. 따라서 검출 신호 크기의 증가를 통한 결함 검출 성능을 향상시키기 위해 논문에서는 브러쉬와 백요크의 크기 및 형상 변화에 따른 자기장 분포 해석을 하고 시스템 제작 및 실험을 통해 자기누설 탐상 시스템의 성능 향상을 검증하였다.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.6
• /
• pp.2218-2223
• /
• 2014

A crack which is axially oriented with small size is hard to detect in conventional system. CMFL(Circumferential Magnetic Flux Leakage) type PIG(Pipelines Inspection Gauge) in the NDT(Nondestructive Testing), is operated to detect this defect called axially oriented cracks in the pipe. It is necessary to decompose the size and shapes of cracks for the maintenance of underground pipelines. This article is mainly focused on the decomposing method of the size and shape of the axially oriented cracks by using inspection signal data for defect.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.5
• /
• pp.765-771
• /
• 2017

This paper presents concurrent design methods of surface permanent magnet synchronous machines for saliency-tracking self-sensing position estimation. Magnetic saliency for the self-sensing is created by stator pole saturation due to the rotor zigzag leakage flux. The power conversion properties such as saliency ratio, torque ripple, and efficiency vary according to motor design. The property change due to design modification is analysed by using finite element analysis, and with the appropriate design modification, proper saliency is created while preserving their power conversion capabilities.

• 전기의세계
• /
• v.24 no.1
• /
• pp.29-42
• /
• 1975

In this paper, the electrical angle between two winding axes in the stator of the capacitor motor is put optional angle, deviding the space harmonics in its magnetic field of two windings and the leakage flux into the forward revolving field and the backward one by the revolving-field theory, its equivalent circuit which consider mutual induction between two windings is depicted. In the depicted equivalent circuit, the rotor resistance for the fundamental flux is devided into the resistance for the rotor bar and endring, and the rotor leakage reactance for the fundamental is devided into the skew leadage reactance and the other, and each circuit constants for each harmonics is expressed in terms of the circuit constants for the fundamental, so it mades easy to determine the characteristics for the capacitor motor. As the circuit constant ratios to the magnetizing reactance of the fundamental are used, motors which have same circuit constant ratios should be resembled in their characteristics.

• Journal of Mechanical Science and Technology
• /
• v.16 no.5
• /
• pp.591-598
• /
• 2002

Leakage magnetic flux is occurred in the cracked area of magnetized specimens, and also it changes the magnetic domain area of the magneto-optical film positioned on the specimen. It causes the change of the optical permeability of the magnetic domain on the crack area. So crack images can be obtained easily using this principle. On the other hand, utilizing a laser in this method makes possible to perform a remote sensing by detecting the light intensity contrast between cracked area and normal area. This paper shows the application of non-destructive inspection system taking advantage of magneto-optical method for micro-cracks and presents examples applied to the several types of specimens having fatigue cracks and fabricated cracks using this method. Also the authors prove the possibility of this method as a remote sensing system under the oscillation load considering application to real fields.

• Journal of Mechanical Science and Technology
• /
• v.14 no.10
• /
• pp.1072-1080
• /
• 2000

Leakage magnetic flux (LMF) is widely used for non-contact detection of cracks. The combination of optics and LMF offers advantages such as real time inspection, elimination of electrical noise, high spatial resolution, etc. This paper describes a new nondestructive evaluation method based on an original magneto-optical inspection system, which uses a magneto-optical sensor, LMF, and an improved magnetization method. The improved magnetization method has the following characteristics: high observation sensitivity, independence of the crack orientation, and precise transcription of the geometry of a complex crack. The use of vertical magnetization enables the visualization of the length and width of a crack. The inspection system provides the images of the crack, and shows a possibility for the computation of its depth.