• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.38-45
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• 2020

A magnetically levitating capsule train, which runs inside the sub-vacuum tube, can reach ultra-fast speeds by dramatically reducing the aerodynamic drag and friction. The capsule train uses the superconductor electrodynamic suspension (SC-EDS) method for levitation. The SC-EDS method has advantages, such as a large levitation gap and free of gap control, which could reduce the infra-construction cost. On the other hand, disadvantages, such as the large variation of the levitation-guidance gap and small damping characteristics in levitation-guidance force, could degrade the running stability and ride comfort of the capsule train. In this study, a dynamic analytical model of a capsule train based on the SC-EDS was developed to analyze the running dynamic characteristics. First, as important factors in the capsule train dynamics, the levitation and guidance stiffness in the SC-EDS system were derived, which depend non-linearly on the velocity and gap variation. A 3D dynamic analysis model for capsule trains was developed based on the derived stiffness. Through the developed model, the effects of the different running speeds on the ride comfort were analyzed. The effects of a disturbance from infrastructure, such as the curve radius, tube sag, and connection joint difference, on the running stability of the capsule train, were also analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.794-801
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• 2017

When a radial wheel is placed so as to partially overlap a conductive plate and rotated, a lift force is generated on the wheel, a thrust force along the edge, and a lateral force which tends to reduce the overlap region. When several of these wheels are combined, it is possible to realize a system in which the stability of the remaining axes is ensured, except in the traveling direction. To validate the overall characteristics of the multi-wheel system, we propose a transfer system levitated magnetically using radial electrodynamic wheels. The proposed system is floated and propelled by four wheels and arranged in a structure that allows the thrusts generated by the front and rear wheels to offset each other. The dynamic stability of the wheel and the effect of the pole number on the three-axial forces are analyzed by the finite element method. At this time, the thrust and levitation force are strongly coupled, and the only factor affecting them is the wheel rotation speed. Therefore, in order to control these two forces independently, we make use of the fact that the ratio of the thrust to the levitation force is proportional to the velocity and is independent of the size of the gap. The in-plane and out-of-plane motion control of the system is achieved by this control method and compared with the simulation results. The experimental results show that the coupled degrees of freedom can be effectively controlled by the wheel speed alone.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.6-8
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• 1995

In this paper, we study the computation of the electric field of dielectric analysis models with the conductivity on its surface. The finite element formulation describes a sinusoidal electrodynamic field computation. One term is added to this functional in order to take the conductivity on its surface into accounts. The electric field computations of the dielectric analysis model are done first with the surface conductivity and second with the volume conductivity. Also, it is shown that a surface conductor with sufficiently large conductivity can be substituted with a floating equipotential line. This method is applied to an insulator in arbitrary shape with the conductivity on its surface.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1159_1160
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• 2009

This paper presents the numerical simulation results on the supercodnucting electrodynamic suspension (EDS) simulator according to the variation of the ground conductor. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible way to simulate the EDS system were simulated in this paper by using finite element method (FEM). The static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.37-41
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• 2008

Superconducting Electrodynamic suspension(EDS) system is generated by the interaction between the magnetic field made by the induced the eddy current in the ground conductor and the moving magnetic field made by onboard superconducting magnet. The levitation force of EDS system, which is proportional to the strength of the moving magnetic field, becomes saturated according to the increase of the velocity. Especially, the levitation force is influenced by the structure of HTS magnet and ground magnet. This paper deals with the optimal design condition for the HTS levitation magnet. The 3-D numerical analysis with FEM was used to find the distribution of the magnetic field, the optimal coil structure, and the calculation of the levitation force.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.786-789
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• 2002

The behaviour of contactors protected by arcs under short-circuit currents is analysed using a simple model to represent the electric circuit and the contactor. In most cases, the protection of contactors against short-circuit currents is entrusted to fuses. Fuses are suitable for preventing excessive damage to the contactor, or parts of the contactor, under short-circuit conditions. In particular, they are capable of limiting the thermal and electrodynamic stresses which can lead to arcing or welding together of the contacts of a contactor. This paper is the Dynamic Motion Analysis of a Moving Contact by Electromagnetic Repulsion Force in Molded Case Circuit Breaker(MCCB)

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.199-201
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• 1994

In this paper, The characteristics of the new superconducting maglev system which has quadruple armature windings is examined. This system can generate guidance force and levitation force as well as propulsion force by single ground coil. The time-domain analysis method and phasor analysis method are derived to analyze the characteristics of the proposed system. From the numerical examples for two kind of armature winding configurations, it is shown that the levitation force and guidance force can be generated by single armature winding of the linear synchronous motor without any other ground coils for levitation and guidance, and that double layer configuration has better characteristics in the qualitive characteristics. like as efficiency, pulsation of the electromagnetic forces and drag ratio, than the single layer configuration.

• Progress in Superconductivity and Cryogenics
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• v.12 no.2
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• pp.21-24
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• 2010

This paper deals with numerical analysis on a high-$T_c$ superconducting (HTS) electrodynamic suspension (EDS) simulator according to the variation of the ground conductor conditions. Because the levitation force of EDS system is formed by the magnetic reaction between moving magnets and fixed ground conductors, the distribution of the magnetic flux on a ground conductor plays an important role in the determining of the levitation force level. The possible way to analyze HTS EDS system was implemented with 3D finite element method (FEM) tool. A plate type ground conductor generated stronger levitation force than ring type ground conductor. Although the outer diameter of Ring3 (335 mm) was larger than that of Ring2 (235 mm), the levitation force by Ring2 was stronger than that by Ring3. Considering the results of this paper, it is recommended that the magnetic flux distribution according to the levitation height and magnet current should be taken into account in the design of the ground conductors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.82-87
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• 2007

A Halbach array is a special arrangement of permanent magnets which augments the magnetic field on one side of the device while cancelling the field to near zero on the other side. The application of this Halbach array magnet to the electrodynamic suspension for Maglev train has been recently studied in order to increase the levitation capability. This paper is focused on analytical method of the magnetic levitation system using Halbach array magnet. The suitability of the proposed method is verified with comparing to a finite element method. From this study, it is confirmed that the proposed method provides a reasonable solution with a little analysis time to the finite element method and the magnetic levitation system using Halbach array magnet is stable dynamically.

• Journal of KSNVE
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• v.8 no.5
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• pp.887-899
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• 1998

It has been resulted that Lagrange multiplier method with statistical approach was superior to traditional harmonic balance method in identifying the nonlinear loudspeaker parameters when output signals were contaminated with Gaussian random noise. We have known that the displacement-dependent characteristic values of nonlinear parameters identified by traditional harmonic balance method were estimated less than original values by the increase of output noise and the stiffness coefficients were very sensitive to output noise. Also, by the sensitivity analysis we have verified that the harmonic distortions in acoustic radiation was mainly due to nonlinearity of force factor caused by uneven magnetic fields and that reducing the nonlinearity of damping coefficients were very effective for improving second harmonic distrotion of acoustic radiation.