• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.166-169
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• 2004

In this paper, computational analysis and experiments of subwoofer for car audio speaker system were performed and discussed to analyze acoustical phenomena for subwoofer. Ported enclosure system with subwoofer were manufactured and provided for test and simulation purposes. Subwoofer with single voice coil and double voice coil were identified by linear and nonlinear parameter identification method for loudspeaker parameters. For high power inputs to subwoofer, sound pressure levels were compared according to input powers with linear and nonlinear loudspeaker models. For subwoofer system with high power nonlinear speaker model was showed to be adequate to describe the behaviour of loudspeaker.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.51-55
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• 2017

To obtain Nuclear Magnetic Resonance (NMR) measurement of membrane protein, an NMR magnet is required to generate high intensity, homogeneity, and stability of field. A High-Temperature Superconducting (HTS) magnet is a promising alternative to a conventional Low-Temperature Superconducting (LTS) NMR magnet for high field, current density, and stability margin. Conventionally, an HTS coil has been wound by several winding techniques such as Single-Pancake (SP), Double-Pancake (DP), and layer-wound. The DP winding technique has been frequently used for a large magnet because long HTS wire is generally difficult to manufacture, and maintenance of magnet is convenient. However, magnetic field generated by the slanted turns and the splice leads to field inhomogeneity in Diameter of Spherical Volume (DSV). The field inhomogeneity degrades performance of NMR spectrometer and thus effect of the slanted turns and the splice should be analyzed. In this paper, field gradient of HTS double-pancake coils considering the slanted turns and the splice was calculated using Biot-Savart law and numerical integration. The calculation results showed that magnetic field produced by the slanted turns and the splice caused significant inhomogeneity of field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.227-231
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• 2014

Underwater radiated noise is one of the vital factors in underwater weapon systems like submarine. A passive elastic mount is an effective reduction method for the vibration from a ship-board machinery transmitted to the hull which is radiated as noise outside the hull. A passive elastic mount shows the limitation on the vibration reduction and needs multi stage mounting system including double stage one to meet the required underwater radiated noise criteria. It is necessary for the multi stage mounting system to consider the large displacement in the underwater shock explosion. So it is difficult to apply the multi stage mounting system in submarine because of space limitation. Also recent navy sonar system are trying to have the capability to detect the ship-borne acoustic signals in the low frequency range. An alternative to the passive mount is an active mount with moving-coil type electromagnetic actuator based on a conventional rubber mount in the low frequency range. In the previous paper, 4 active mounts with moving-coil type electromagnetic actuator based on the rubber mount were installed on the hard floor of the facility, which means no consideration on the elastic foundation effect for the control of the active mounts was taken into account. In this study, an experimental performance analysis on the active mount was carried out using 4 active mounts installed on the cylindrical structure to investigate the elastic foundation effect.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.195-197
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• 1993

In this paper, a planar vibratory gyroscope is designed and fabricated in macro model. Elementary experiment and test are done for micro model. This gyroscope has a double gimbal structure with an active dimension $80{\times}120{\times}1\;mm^3$. Outer gimbal vibration is generated by electromagnetic force using ferrite E-core wounded by coil. Inner gimbal vibration is detected by inductive sensor. It is demonstrated' that mechanical and electrical symmetries are important for improvement of vibratory gyroscope.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.62-64
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• 1995

This paper describes the characteristics of electromagnetic forces of Combined superconducting maglev system. Generation of the levitation, the propulsion and the guidance force by a single coil is proved by the phasor- analysis. It is also shown that double-layered configuration has better characteristics in efficiency, pulsation of the forces and drag ratio than single-layered configuration.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.92-96
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• 2003

This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1292-1298
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• 2003

In this paper, dc reactor lot the inductive high-Tc superconducting fault current limiter (SFCL) was optimally designed by finite element method(FEM). The Prototype high-Tc do reactor was manufactured and compared to the results of design. This dc reactor consists of 4∼stacked double pancake coils which are wounded with Bi-2223 wire coated with SUS315L. Kapton tape is used for the insulation of turn to turn and layer to layer. Each pancake is connected in series by soldering Finally, optimal design and manufacture method lot the dc reactor is suggested in this paper. Through the comparison of result of optimal design and experimental result of prototype high-Tc superconducting dc reactor, reliance on the design of the high-Tc dc reactor tot the 1.2 kV/80 A SFCL is proved.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.373-377
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• 1999

HTS magnet operated at 20${\sim}$40 K was fabricated using three pieces of 100 m Bi-2223 high temperature superconductors fabricated by powder-in-tube process. It was composed of 6 double pancakes with 75 ID. and 113 OD. connected by lab splice. Coil I$_c$ of each DP.(double pancake) obtained for a 140 turn, fabricated using react and wind procedure was 6${\sim}$8 A at 77 K, self field. The maximum field was measured 0.06 T at lop = 5 A, 77 K. The joint resistance due to lap splice of HTS tapes affect badly to operate HTS magnet with persistent current mode, total effective magnet resistance included lap splice was 55 ${\mu}$ ${\omega}$ at 77 K.

• 전기학회논문지
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• 제56권12호
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• pp.2135-2144
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• 2007

This paper presents system design of the slotless double-side Permanent Magnet Linear Synchronous Machine system (PMLSM) through magnetic field analysis and dynamic modeling. In our analysis, 2-D analytical treatments based on the magnetic vector potential were adopted to predict magnetic field with space harmonics by PM mover magnetization and stator winding current. From these, the design parameters such as inductance, Back-emf, and thrust are estimated. And, the electrical dynamic modeling including synchronous speed is completed by calculation of a DC link voltage in effort to obtain the accurate mechanical power from Space Vector Pulse Width Modulation(SVPWM). Therefore, the system design of PMLSM is performed from estimation of design parameters according to PM size and coil turns in magnetic field and from calculation of a DC link voltage to satisfy base speed and base thrust represented as the maximum output power in dynamic modeling. The estimated values from the analysis are verified by the finite element method and experimental results.

• 한국초전도ㆍ저온공학회논문지
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• 제23권2호
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• pp.24-27
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• 2021

This paper presents a design methodology of high-temperature superconducting (HTS) magnets. The magnet consists of several double pancake coils with a variety of wire width. This technique, named Multi-Width, is well known to make efficient use of the superconducting wire. It is common for design of high-temperature superconducting magnets to not only reduce wire consumption used, but also consider the homogeneity of the magnetic field. In this paper, we study a design method that efficiently reduces wire usage while considering magnetic field homogeneity. The design is carried out by calculating the critical current and the critical magnetic field according to the configuration of arranging the thickness of the wire to determine the number of windings. The width of wire comprising the magnet was set to 4 - 12 mm, and the number of double pancake coils was set to an even number to consist of top-down symmetry. To verify the validity of the design, we compared the progress of the design code with a complete enumeration survey. As a case study, we designed a magnet that generates a central magnetic field of 3 T or more in a 240 mm bore in diameter. Optimality can be evaluated by weighing wire consumption and field homogeneity according to the magnet's use or user preference.