• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.78-81
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• 2003

In this paper, we analyze the transient electromagnetic response from three-dimensional dielectric bodies using a time-domain PMCHW (Poggio, Miller, Chang, Harrington, Wu) formulation. The time-domain unknown coefficients of the equivalent currents are approximated by a set of orthonormal basis functions that are derived from the Laguerre polynomials. Numerical results computed by the proposed method are presented.

• Journal of Magnetics
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• v.20 no.3
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• pp.322-329
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• 2015

This paper presents a new overlapped coilgun configuration to launch medium weight projectiles. The proposed configuration consists of a two-stage coilgun with overlapped coil covers with spacing between them. The theoretical operation of a multi-stage coilgun is introduced, and a transient simulation was conducted for projectile motion through the launcher by using a commercial transient finite element software, ANSOFT MAXWELL. The excitation circuit design for each coilgun is reported, and the results indicate that the overlapped configuration increased the exit velocity relative to a non-overlapped configuration. Different configurations in terms of the optimum length and switching time were attempted for the proposed structure, and all of these cases exhibited an increase in the exit velocity. The exit velocity tends to increase by 27.2% relative to that of a non-overlapped coilgun of the same length.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1822-1824
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• 1996

Damage and upset of control and communication equipment due to transient overvoltages which occur due primarily to internal switching surge and external lightning surge are an important problems in electromagnetic compatibility(EMC). In this paper, we analyzed operation characteristic of metal oxide varistor widely used low voltage AC line using the electromagnetic transients program(EMTP) and compare it with experimental results and also, we modeled combination generator producing $1.2/50{\mu}s$ open circuit voltage and $8/20{\mu}s$ short circuit current as a source which is critical in calculating operation characteristic. Simulation results showed that most of Transient energy consumes at MOV located in service entrance side than load side, and it showed similar to experimental results. Therefore, entrance side MOV should be selected more energy capacity than that of load side MOV.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.959-965
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• 2002

It is intended to develop an algorithm for dynamic simulation of a fast-acting solenoid valve. The coupled equations of electric, magnetic, and mechanical systems should be solved simultaneously in a transient nonlinear manner. The transient nonlinear electromagnetic field is analyzed by the Finite Element Method (FEM), which is coupled with nonlinear electronic circuitry. The dynamic movement of the solenoid valve is analyzed at every time step from the force balance acting on the plunger, which includes the electromagnetic force calculated from the Finite Element analysis as well as the elastic force by a spring and the hydrodynamic pressure force along the flow passage. Dynamic responses of the solenoid valves predicted by this algorithm agree well with the experimental results including bouncing effects.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1843-1846
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• 1997

This paper describes the fault reducing effects of the 154 kV transmission tower by auxiliary grounding from the top of the tower to ground. The grounding surge impedance of the auxiliary grounding system is calculated by CDEGS(:Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis), and the critical lightning back flashover current and arcing horn dynamic characteristics are simulated by EMTP/TACS(:Electromagnetic Transient Program/Transient Analysis of Control Systems). The calculated results of total LFOR(Lightning Flashover Rate) shows that the LFOR can be reduced from 5.2(count/100km. year) to 3.4 by auxiliary grounding on the 154 kV transmission tower with one ground wire shielding system.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.369-374
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• 2011

An induction motor operated with high voltage source generally generates high current in starting mode and has a long transient time after being started. This large and sustaining starting current causes the end windings of the stator to have excessive electromagnetic force. This force is the source of vibration and has a negative and serious influence on the insulation of end windings. Therefore, designing the end winding part with an appropriate support system is needed. To design the support ring enclosing the end windings, we analyze the distribution of electromagnetic force on the end windings by applying the Biot-Savart's law and the 3D finite element method (FEM), and comparing two simulation methods. Finally, we verify the safety of the support structure of the end winding part using stress analysis, which is analyzed with the electromagnetic forces from the 3D FEM simulation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.11
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• pp.559-566
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• 2002

In this paper, we present an accurate and stable method for the solution of the transient electromagnetic response from the conducting wire structures using the time domain integral equation. By using an implicit scheme with the central finite difference approximation for the time domain electric field integral equation, we obtain the transient response from a wire scatterer illuminated by a plane wave and a conducting wire antenna with an impressed voltage source. Also, we consider a wire above a 3-dimensional conducting object. Numerical results are presented, which show the validity of the presented methodology, and compared with a conventional method using backward finite difference approximation.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.843-847
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• 1988

In electromagnetic transient analysis studies, complex transmission system should be modelled in detail. But in large system, modelling of complete system is a big burden in many sides such as computation time, modelling efforts. It is needed to model only a concerned part of the system in detail. The remaining parts of the system have to be reduced to equivalents. This study suggests a method of generating a simple network equivalents which has equivalent frequency charastics in wide frequency range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.83-93
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• 1997

This paper deals with measurements and evaluation of the time-changing electric and magnetic fields at a high-voltage laboratory. The electromagnetic disturbances originate mainly from ground faults and on/off operations of electric power equipments. The electronic circuits and control devices are very sensitive to electromagnetic interferences. It is necessory to evaluate the levels of interferences for a given electromagnetic environment. The electric field was observed by the electric field sensor having the bandwidth of the range from 40 Hz to 200 MHz, and the time-changing magnetic field was measured by the loop sensor of which the output is directly proportional to the incident signal. Also, the frequency components of the time-changing electric and magnetic fields induced by an oscillatory transient current and a chopped impulse voltage were analyzed by terms of the fast Fourier transformation, and those give the information about the levels of the electromagnetic interferences and the design of the electromagnetic shielding enclosures.

• Transactions of Materials Processing
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• v.16 no.2 s.92
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• pp.113-119
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• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat material by means of an electric current that is caused to flow through the material or its container by electromagnetic induction. It has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers a finite element analysis of the induction heating process which can rapidly raise mold temperature. To simulate the induction heating process, the electromagnetic field analysis and transient heat transfer analysis are required collectively. In this study, a coupled analysis connecting electromagnetic analysis with heat transfer simulation is carried out. The estimated temperature changes are compared with experimental measurements for various heating conditions.