• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.10
• /
• pp.1426-1431
• /
• 2012

This paper analyzes re-degaussing performances of various breakdown conditions of degaussing coils in a ship to reduce underwater magnetic field anomaly due to the hull magnetization induced under the Earth's magnetic field. To achieve this, first, it is implemented to optimize degaussing coil currents by a magnetomotive force sensitivity formula combined with the coil effects. The re-degaussing processes are then executed when a breakdown occurs in degaussing coils, one by one. Finally, the re-degaussing performances are examined with the results of normal degaussing and coil breakdown conditions.

• Journal of Magnetics
• /
• v.21 no.2
• /
• pp.197-203
• /
• 2016

A naval ship equipped with a degaussing system may undergo a breakdown in degaussing coils at sea. In the case, underwater magnetic field around the ship abruptly grows up and it can make the ship be easily exposed to fatal hazards such as magnetic mines or torpedoes. This paper proposes an efficient and practical re-degaussing technique for a ship where a part of degaussing coils is out of order. To achieve this, an analytical design sensitivity formula and approximated degaussing coil field are exploited, and then new optimum currents of available coils are reassessed. To validate the proposed method, a muck-up ship equipped with 14 degaussing coils is tested in scale-down magnetic treatment facilities under three faulty coil conditions.

• Journal of the Korean Magnetics Society
• /
• v.24 no.4
• /
• pp.107-113
• /
• 2014

In this paper, a optimum degaussing technique, which can minimize an underwater magnetic field anomaly generated by the ferromagnetic hull, was verified through the mock-up test of a ship. To predict degaussing field signals due to the degaussing coils installed in a ship, individual coil effects were measured. Exploiting the linearity of coil effects and analytical sensitivity formula, optimum degaussing current values fed to individual coils were decided. To identify degaussing performance of the proposed method, the obtained degaussing currents were applied to the coils. Then the field anomaly signals were measured and analyzed before and after degaussing. Experimental results show the magnitude of the field signal after degaussing is reduced up to 95% of that before degaussing.

• Journal of Magnetics
• /
• v.18 no.2
• /
• pp.135-141
• /
• 2013

This paper proposes an efficient fault detection method for onboard degaussing coils which are installed to minimize underwater magnetic fields due to the ferromagnetic hull. To achieve this, the method basically uses field signals measured at specific magnetic treatment facilities instead of time-consuming numerical field solutions in a three-dimensional analysis space. In addition, an analytical design sensitivity formula and the linear property of degaussing coil fields is being exploited for detecting fault coil positions and assessing individual degaussing coil currents. Such peculiar features make it possible to yield fast and accurate results on the fault detection of degaussing coils. For foreseeable fault conditions, the proposed method is tested with a model ship equipped with 20 degaussing coils.

• Journal of the Korean Magnetics Society
• /
• v.27 no.3
• /
• pp.98-103
• /
• 2017

In this paper, an efficient closed-loop degaussing technique is proposed to control real-time degaussing currents required for a minesweeper. To achieve this, new principle and algorithm for controling degaussing currents are presented, and they are compared to conventional ones. To validate the proposed method, a minesweeper mockup is tested by means of a rigorous numerical simulation. Results show that the method successfully yields satisfactory degaussing performances for several course angle changes of the mockup.

• Journal of Magnetics
• /
• v.19 no.1
• /
• pp.72-77
• /
• 2014

This paper proposes an indirect fault detection method for an onboard degaussing coil system, installed to reduce the underwater magnetic field from the ferromagnetic hull. The method utilizes underwater field signals measured at specific magnetic treatment facilities instead of using time-consuming numerical field solutions in a three-dimensional space. An equivalent magnetic charge model combined with a material sensitivity formula is adopted to predict fault coil locations. The purpose of the proposed method is to yield reliable data on the location and type of a coil breakdown even without information on individual degaussing coils, such as dimension, location and number of turns. Under several fault conditions, the method is tested with a model ship equipped with 20 degaussing coils.

• Journal of the Korean Magnetics Society
• /
• v.27 no.2
• /
• pp.63-69
• /
• 2017

Naval ships are particularly required to maintain acoustic and magnetic silence due to their operational characteristics. Among them, underwater magnetic field signals derived by ships are likely to be detected by threats such as surveillance systems and mine systems at close distance. In order to increase the survivability of the vessels, various techniques for reducing the magnetic field signal are being studied and it is necessary to consider not only the magnitude of the magnetic field signal but also the gradient of it. In this paper, we use the commercial electromagnetic finite element analysis tool to predict the induced magnetic field signal of ship's scaled model, and arrange the degaussing coil. And the optimum degaussing current of the coil was derived by applying the particle swarm optimization algorithm considering the gradient constraint. The validity of the optimal degaussing technique is verified analytically by comparing the magnetic field signals after the degaussing with or without gradient constraint.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2013.12a
• /
• pp.17-19
• /
• 2013

• Journal of the Korean Magnetics Society
• /
• v.21 no.5
• /
• pp.167-173
• /
• 2011

Underwater static magnetic field signature for the naval ship has been widely used as the detonating source of the influence mine system because it is possible to make an accurate target detection in the near field although the magnetic field falls off relatively fast with distance in comparison with the underwater radiated noise signal. In this paper, we describe the prediction results about the underwater static magnetic field by the ferromagnetic hull, the internal structures and the main on-board equipment for the target vessel using the commercial FEM software. Also we analyze the degaussing effectiveness for the target vessel through the degaussing coils arrangement.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1005-1006
• /
• 2011

함정 내부에 설치된 소자 코일의 기하학적 정보를 알 수 없을 때에도 소자 코일 전류 최적화를 수행하고자 코일 효과와 기자력 민감도를 이용한 최적화 기법을 바탕으로 가상영역 내에 구축된 코일을 이용하는 소자 코일 전류 최적화를 수행하는 기법을 제시하였다. 민감도 특성을 기반으로 가상영역 내에 임의의 소자 코일을 구축하였으며 이에 따른 특성을 분석하였다. 그리고 정상 상태의 소자상태, 전류 최적화 결과를 비교함으로서 제안한 기법의 활용 가능성을 확인하였다.