• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.147-152
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• 1999

Semiconductor piezoresistive type vibration sensor was fabricated by using semiconductor process and micromachining technology. To measure the micro electromagnetic force between coil and magnet, fabricated vibration sensor was used. Toapply micro electromagnetic force produced from the micro exciter, small-sized NdFeB permanent magnet was attached on the mass of the fabricated vibration sensor. The measured electromagnetic force are about 5~180dyne when the applied sinusoidal current of 1KHz in the range of 1.5~8mA. The measurement of micro electromagnetic forcewas performed by changing the distance between coil and magnet. Output characteristics of micro electromagnetic force according to the applied coil current were linear. Furthermore, output results were used to get the transfer constant that is important to decide the efficiency and the performance of the coil and magnet.

• Journal of Magnetics
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• v.18 no.4
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• pp.481-486
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• 2013

An electromagnetic launcher (EML) system accelerates and launches a projectile by converting electric energy into kinetic energy. There are two types of EML systems under development: the rail gun and the coil gun. A railgun comprises a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail, but the high mechanical friction between the projectile and the rail can damage the projectile. A coil gun launches the projectile by the attractive magnetic force of the electromagnetic coil. A higher projectile muzzle velocity needs multiple stages of electromagnetic coils, which makes the coil gun EML system longer. As a result, the installation cost of a coil gun EML system is very high due to the large installation site needed for the EML. We present a coil gun EML system that has a new structure and arrangement for multiple electromagnetic coils to reduce the length of the system. A mathematical model of the proposed coil gun EML system is developed in order to calculate the magnetic field and forces, and to simulate the muzzle velocity of a projectile by driving and switching the electric current into multiple stages of electromagnetic coils. Using the proposed design, the length of the coil gun EML system is shortened by 31% compared with a conventional coil gun system while satisfying a target projectile muzzle velocity of over 100 m/s.

• Transactions of Materials Processing
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• v.23 no.7
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• pp.431-438
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• 2014

For electromagnetic forming(EMF) the most important feature is a forming coil which creates the electromagnetic force(Lorentz force), using current density and a magnetic field. Most previous papers have concentrated on the final configuration of the blank or the efficiency of EMF process. Studies focused on the design parameters affected by the forming coil performance have not been conducted. In order to design a suitable forming coil for an object, the current study uses LS-DYNA EM-Module to not only optimize the coil but also to examine the effect of coil performance. By this method a suitable forming coil was made and tested to determine whether or not good formability was achieved in a free bulge test Numerical analysis was also used. The workpiece was Al 1100-O with a thickness of 1.27mm and the coil was made from copper CW004A, which has good electrical conductivity and is suitable for electrical components.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.292-297
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• 2011

MPF(Magnetic pulse forming) process refers to the high velocity and high strain rate deformation of a low-ductility materials driven by electromagnetic forces that are generated by the rapid discharge current through forming coil. The goal of this study was to find the characteristics of dynamic behavior of workpiece and to find the main design process on MPF using bar forming coil. For these purposes, thin Al5053 sheet were used for the experiment. The measured strain data were analyzed by developed electromagnetic FE-model. The main design parameter is location of coil, electromagnetic force. In case of the bar forming coil, there exists the dead regions where the low electromagnetic force applied on the workpiece.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.822_823
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• 2009

Superconducting fault current limiters (SFCLs) provide one of the most effective solutions to cope with enormous increase of fault current level. The 13.2 kV/ 630 A class resistive SFCL using coated conductor (CC) was developed and its short-circuit test was successful. Successful commercialization of the SFCL requires that no loss is produced by impedance of limiting coil during normal operation. Since the limiting coil consists of inner layer and outer layer, gap length between the layers is an important parameter to analyze the electromagnetic characteristics of coil. This paper deals with the electromagnetic characteristics of coil according to gap length through the simulation and analysis in comparison with experiment results.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.5
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• pp.315-320
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• 2000

This paper presents the fabrication and test of a micropump with an electromagnetic actuator and a pair of aluminum flap valves. The actuator consists of a solenoid coil, a permanent magnet and an actuator diaphragm. The actuator diaphragm is fabricated by the spin coating of silicone rubber. The valve are passive ones and are fabricated by micromachining. The deflection of the fabricated actuator diaphragm is measured with a laser vibrometer. The deflection of the actuator diaphragm is proportional to the input current. The measured deflection of the fabricated diaphragm is $400 \mum$,/TEX> when the input is 118 mApp, and the cut-off frequency is 50 Hz. The maximum flow rate of the fabricated micropump with the electromagnetic actuator is about 5$0 \muell/min$ at 5 Hz when the input current and the duty ratio of the square was are 118 mApp and 50%, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3455-3459
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• 2014

This paper reports the design and experiments for a high drive force of projectile in a coil gun system. Currently, the coil gun has been studied to apply an electromagnetic launcher. A coil gun launches a projectile by the attractive magnetic force of the electromagnetic coil. The drive force of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coil gun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. For this purpose, this study calculated the magnetic flux density and forces of the coil gun system and determined the current limit of the coil using the Onderdonk's equation. Based on the design result, a prototype was manufactured and an experiment was conducted to measure the muzzle velocity of the projectile. The fired projectile was analyzed using a CCD camera, and the muzzle velocity was 21m/s. In addition, a comparison of the experimental value and analysis value using commercial electromagnetic analysis software MAXWELL revealed an error of approximately 9.5%.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.991-993
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• 1999

The method of measurement for contactless eddy-current conductivity using magnetic dipole field theory was suggested by M.C Chen[1], which calculate the eddy-current caused by exciting coil with Faraday's induction law. In this work, we have developed the apparatus for contactless measurement of conductivity or resistivity with the dipole field theory. The resistivity can be measured from several to a dozen $m{\Omega}{\cdot}cm$ range within maximum 30% error. At the high resistivity range above $100{\Omega}{\cdot}cm$, the standard deviation of measurement was very large as the induced voltage of sensing coil is small so it was difficult to measure the value precisely.

• Transactions of Materials Processing
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• v.28 no.3
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• pp.135-144
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• 2019

Electromagnetic impulse welding (EMIW) is a type of solid state welding using the Lorentz force generated by interaction between the magnetic field of the coil and the current induced in the workpiece. Although many experimental studies have been investigated on the expansion and compression welding of tube using the EMIW process, studies on the EMIW process of lap joint between flat sheets are uncommon. Since the magnetic field enveloped inside the tube can be controlled with ease, the electromagnetic technique has been widely used for tube welding. Conversely, it is difficult to control the magnetic field in the flat sheet welding so as to obtain the required welding velocity. The current study analyzed the effects of coil shape on the impulse velocity for suitable flat one-turn coil for the EMIW of the flat sheets. The finite element (FE) multi-physics simulation involving magnetic and structural field of EMIW were conducted with the commercial software LS-DYNA to evaluate the several shape variables, viz., influence of various widths, thicknesses, gaps and standoff distances of the flat one-turn coil on the impulse velocity. To obtain maximum impulse velocity, the flat one-turn coil was designed based on the FE simulation results. The experiments were performed using an aluminum alloy 1050 sheets of 1.0mm thickness using the designed flat one-turn coil. Through the microscopic interfacial analysis of the welded specimens, the interfacial connectivity was observed to have no defects. In addition, the single lap joint tests were performed to evaluate the welding strength, and a fracture occurred in the base material. As a result, a flat one-turn coil was successfully designed to guarantee welding with bond strength equal to or greater than the base material strength.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.733-740
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• 2013

The high-velocity electromagnetic forming (EMF) process is based on the Lorentz force and the energy of the magnetic field. The advantages of EMF include improved formability, wrinkle reduction, and non-contact forming. In this study, numerical simulations were conducted to determine the practical parameters for the EMF process. A 2-D axis-symmetric electromagnetic model was used, based on a spiral-type forming coil. In the numerical simulation, an RLC circuit was coupled to the spiral coil to measure various design parameters, such as the system input current and the electromagnetic force. The simulation results show that even though the input peak current levels were at the same level in each case, the forming condition varied due to differences in the frequency of the input current. Thus, the electromagnetic forming force was affected by the input current frequency, which in turn, determined the magnitude of the current density and the magnetic flux density.