• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.250-255
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• 2008

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression. principle of virtual work is adapted. And this theory was programming using MATLAB software. To compare FEM using MATLAB software was applied MSC. Nastran software. The geometry model for MSC. Patran was produced by 3-D design modeling software. Finite element model was produced by MSC. Patran. Finite element was applied tetra (CTETRA) having 10 node. The analysis results of the MATLAB and MSC. Nastran are fairly well agreed with those of various experiments. Using MATLAB program proposed in this paper and MSC. Nastran, spring constants and stresses can be predicted by input of few factors.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.317-323
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• 2001

We investigated the stability of cryocooler-cooled high-temperature superconducting (HTS) coils by using a computer program based on FEM. In this study, the current at which "thermal runaway" occurs, which depends on the relationship between the cooling power of the cryocooler and the heat generation in HTS coils, was adopted as a stability criterion of cryocooler operating HTS coils. It was shown that cryocooler-cooled HTS coil was stable in operating current above the critical current from the numerical analysis results by HTS model coil. And also, if we efficiently remove the heat generation from HTS coils by potimizing heat drain, the ramp-rate limitation can be mitigated because the effect of AC loss by the current rise was too small. Furthermore, in the case of pulsed operation; the HTS model coil is ramped from zero to the peak value in one second and back to zero current in one second, such as the operation of SMES device, the peak value of poerating current is 1.5-2 times greater than that of the thermal runaway current.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.147-154
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• 2016

Co-nonsolvency is a puzzling phenomenon that a polymer swells in a good solvent individually, but it collapses in a mixture of good solvents. This structural transition with changing solvent environment has been drawing attention due to practical application for stimuli-responsive polymer. The aim of this work is to describe the physical origin of the co-nonsolvency. In this work, we present Monte Carlo simulations for polymer solutions by using simple and general model. We simulate linear and ring polymers to compare their co-nonsolvency behaviors. Calculating Flory exponents and bridging fractions gives a good description for polymer structures. While the polymer structure shows non-monotonous behavior with increasing the cosolvent fraction, the chemical potential decreases monotonously. This indicates that coil-to-globule transition of polymers is purely controlled by free energy and can be regarded as a thermodynamics transition. We also present that ring polymers have higher looping probability than linear polymers, thus the bridging fraction remains higher at high cosolvent fraction. Our study provides a new perspective to understand polymer structure when the polymer "dissolves well" in any solvent.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.26-30
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• 2018

The turn-to-turn contact resistance of 2G high temperature superconducting (HTS) coils with metal insulation (MI) is closely related to the stability of the coils, current charging rate and delay time [1]. MI coils were fabricated using five kinds of metal tapes such as aluminum (Al) tape, brass tape, stainless steel (SS) tape, copper (Cu)-plated tape and one-sided Cu-plated SS tape. The turn-to-turn contact surface resistances of co-winding model coils using Al tape, brass tape, and SS tape were 342.6, 343.6 and $724.8{\mu}{\Omega}{\cdot}cm^2$, respectively. The turn-to-turn contact resistance of the model coil using the one-sided Cu-plated SS tape was $ 248.8{\mu}{\Omega}{\cdot}cm^2$, which was lower than that of Al and brass tape. Al or brass tape can be used to reduce contact resistance and improve the stability of the coil. Considering strength, SS tape is recommended. For strength and low contact resistance, SS tape with copper plating on one side can be used.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.45-49
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• 2015

It has been well known that a toroid is the inevitable shape for a high temperature superconducting (HTS) coil as a component of a large scale superconducting magnetic energy storage system (SMES) because it is the best option to minimize a magnetic field intensity applied perpendicularly to the HTS wires. Even though a perfect toroid coil does not have a perpendicular magnetic field, for a practical toroid coil composed of many HTS pancake coils, some type of perpendicular magnetic field cannot be avoided, which is a major cause of degradation of the HTS wires. In order to suggest an optimum design solution for an HTS SMES system, we need an accurate, fast, and effective calculation for the magnetic field, mechanical stresses, and stored energy. As a calculation method for these criteria, a numerical calculation such as an finite element method (FEM) has usually been adopted. However, a 3-dimensional FEM can involve complicated calculation and can be relatively time consuming, which leads to very inefficient iterations for an optimal design process. In this paper, we suggested an intuitive and effective way to determine the maximum magnetic field intensity in the HTS coil by using an analytic and statistical calculation method. We were able to achieve a remarkable reduction of the calculation time by using this method. The calculation results using this method for sample model coils were compared with those obtained by conventional numerical method to verify the accuracy and availability of this proposed method. After the successful substitution of this calculation method for the proposed design program, a similar method of determining the maximum mechanical stress in the HTS coil will also be studied as a future work.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.673-675
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• 2002

In this paper. the lumped electrical circuit approach of mass/spring system is used to model the mechanical aspects according to the frequency. Therefore, the mass/spring system can be dealt with here and linked with the equivalent circuit of electric linear oscillatory actuator(LOA). Analysis models are double-coil type linear compressor for stirling refrigerator. The compressor consists of the moving coil LOA, piston, and spring. The electro-mechanical system with mass and spring can be represented using the lumped electrical circuit. We present the system impedance and dynamics of moving coil linear compressor.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.732-734
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• 2002

The rotor thermal analysis consists of determining the heat load to the rotor, sizing the cryogenic system, and ensuring that the HTS rotor will operate at the design goal of 30 K. The heat load to the rotor is due to heat conduction through the torque tubes, current leads, instrumentation. and radiation from the thermal shield and the end caps. Coil operating temperature is determined from the coil losses and the heat transport to the coolant. An FEM thermal conductivity model is developed to allow calculation of heat transport in HTS field coil according to the heat exchanger shape and coolant feeding method. The losses determine the size of the cryocooler.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2219-2226
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• 2017

This paper deals with artificial neural network approach for automatic detection of severity level of stator winding fault in induction motor. The problem is faced through modelling and simulation of induction motor with inter coil shorting in stator winding. The sum of the absolute values of difference in the peak values of phase currents from each half cycle has been chosen as the main input to the classifier. Sample values from workspace of Simulink model, which are verified with experiment setup practically, have been imported to neural network architecture. Consideration of a single input extracted from time domain simplifies and advances the fault detection technique. The output of the feed forward back propagation neural network classifies the short circuit fault level of the stator winding.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.772_773
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• 2009

A numerically efficient performance analysis method for Thomson coil actuator of an arc eliminator is developed by transferring the problem to an equivalent circuit model considering the distribution of eddy current in conducting plate. Through a numerical analysis, the developed method is proven to give a solution, with only 1.3% of computing time, as accurate as finite element method. The developed method is testified by comparing with FEM calculation and experiment results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.3
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• pp.89-98
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• 1998

Some analytic results for a solenoid eddy current coil to test nondestructive conducting materials are described in this paper. Normalized impedance of solenoid coil encircling cylindrical conducting tubes or tow-conductor rods is analyzed. Electrical and magnetic properties such as conductivity, permeability and exciting frequency as well as the geometric ones of fill factor or radius ratio of the conductor are also considered. Impedance characteristics of the models obtained by numerical analysis are examined. Validation of the model is carried out using several samples of non-ferromagnetic conducting tubes and 2-conductor rods.