• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.412-417
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• 1998

This paper suggests the drive characteristics of a Switched Reluctance Motor(SRM) by 2-phase excitation method. T This scheme excites 2 phases simultaneously, which is similar to 2-phase excitation method of a step motor. In this s scheme. the torque is produced by mutual inductances as well as self inductances. The abrupt change of a phase e excitation produces mechanical stresses and it results in vibration and noise. The acoustic noise is reduced remarkably t through the sequential phase excitation in the 2-phase excitation. Operational principle and characteristic comp없1son t to that of the conventional SRM show that this excitation scheme has some advantages including torque ripple and n noise reduction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1466-1477
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• 2016

This paper analyzes the electrical characteristic such as the impedance(Z), inductance(L), and cable resistance($R_p$) according to the change of cable length in order to move the electrical sorting device for distinguishing between AF non-insulated track circuits from the center of railway to outside railway. The simulation is performed to check the voltage difference between the voltage of sender and the voltage of receiver and determine the possibility of the voltage restoration availability in the frequency filter band through the capacitor compensation. It was applied to the results of the simulation to the sorting devices installed in the actual field. It is proved the availability by checking the measured voltage characteristic according to the capacitor compensating change of $10{\mu}F$ and $16{\mu}F$ before, and after the length of cable is increased with 6 meters. Through this, the prevention of breakdown and damage to facilities and the prevention the safety-related accidents of line workers from the train are expected according to moving the sorting devices of AR non-insulated track circuits to outside railway.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1819-1821
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• 1996

A compact size high voltage pulse generator with nanosecond rise time has been fabricated and investigated experimentally. It can be reduced the inductance of the generator by fixing the Marx generator components and pulse forming network components into a single cylindrical unit. As a result, it can be obtained nanosecond rise time about $8{\sim}10[ns]$ and pulse width of several hundred nanoseconds from the modified Marx pulse generator. And parametric studies showed that the rise time of the output pulse was depended little on the change of the load resister and the charging capacitor while the pulse width of the output pulse was depended greatly upon the change of the load resistor and the charging capacitor.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1870-1872
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• 2003

High voltage pulse generator with fast rise time has been studied theoretically and experimentally. The complexity and stray inductance of a pulse generator components can be very difficult to reduce. As a result, a compact size and stable Pulse can be obtained by using a rotary air-hole. Parametric studies showed that the rise time of the output pulse was depended little on the change of the revolutions per minute(RPM) while the pulse width of the output pulse was depended greatly upon the change of the revolutions per minute (RPM).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.185-191
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• 2010

This paper describes a new position sensorless control for the switched reluctance motor (SRM) by monitoring the rate of change of current with respect to the inductance variation. Two consecutive switch-on times in hysteresis current control are compared to calculate the rate of change of current and hence to estimate the rotor position and speed. The proposed sensorless control algorithm is simple to implement as it does not depend on extensive computation or additional hardware. Simulation and experimental results are presented to demonstrate the feasibility of the proposed sensorless control method.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.1
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• pp.1-7
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• 1999

In order to determine the mode I stress intensity factor ($K_I$) by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for a paramagnetic material containing a two-dimensional surface crack was examined. The cause of the change in potential drop and the effects of the magnetic flux and the demagnetization on the change in potential drop were clarified by using the measuring systems with and without removing the magnetic flux from the circumference of the specimen. The change in potential drop was linearly decreased with increasing the tensile load and was caused by the change in conductivity near the crack tip. The reason of decreasing the change in potential drop with increasing the tensile load was that the increase of the conductivity near the crack tip due to the tensile load caused the decreases of the resistance and internal inductance of the specimen The relationship between the change in potential drop and the change in $K_I$ was not affected by demagnetization and was independent of the crack length.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.983-989
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• 2015

Power transformer is one of the major and key apparatus in electric power system. Monitoring and diagnosis of transformer fault is necessary for improving the life period of transformer. The failures caused by short circuits are one of the causes of transformer outages. The short circuit currents induce excessive forces in the transformer windings which result in winding deformation affecting the mechanical and electrical characteristics of the winding. In the present work, a transformer producing only the radial flux under short circuit is considered. The corresponding axial displacement profile of the windings is computed using Finite Element Method based transient structural analysis and thus obtained displacements are compared with the experimental result. The change in inter disc capacitance and mutual inductance of the deformed windings due to different short circuit currents are computed using Finite Element Method based field analyses and the corresponding Sweep Frequency Responses are computed using the modified electrical equivalent circuit. From the change in the first resonant frequency, the winding movement can be quantified which will be useful for estimating the mechanical withstand capability of the winding for different short circuit currents in the design stage itself.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.54-61
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• 2000

In order to determine the mode I stress intensity factor ($K_I$) by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for a paramagnetic material containing a two-dimensional surface crack was examined. The cause of the change in potential drop and the effects of the magnetic flux and the demagnetization on the change in potential drop were clarified by using the measuring systems with and without removing the magnetic flux from the circumference of the specimen. The change in potential drop was linearly decreased with increasing the tensile load and was caused by the change in conductivity near the crack tip. The reason of decreasing the change in potential drop with increasing the tensile load was that the increase of the conductivity near the crack tip due to the tensile load caused the decreases of the resistance and internal inductance of the specimen. The relationship between the change in potential drop and the change in $K_I$ was not affected by demagnetization and was independent of the crack length.

• Journal of IKEEE
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• v.25 no.3
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• pp.534-539
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• 2021

Induction heating method that allows the maximum heating power to be delivered by varying switching frequency in the inductance change of the work coil of induction heater was proposed in this paper. Depending on the type of work piece in the work coil and proximity to the work coil, the resonance frequency of the resonant circuit will be changed. It may be difficult to deliver the maximum power due to the damage of the induced heater element or switching loss depending on the resonance frequency and switching frequency operating relationship. The switching frequency was variable to maintain the maximum power transmission by sensing the heating power due to the change of the resonance frequency. Through the result of the proposed method that can be controlled within the required output change range according to the change of the switching frequency corresponding to the change of the resonance frequency, the induction heater having a variable switching frequency characteristic that can transmit almost constant output power (within 0.43 dB) power efficiency was achieved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.8
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• pp.24-32
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• 2000

In this paper, we have designed and fabricated a new type power divider to be efficient to a size and electrical performance by folding each quarter-wavelength 70.7 Ω section into a tightly-coupled "meander-line" and inserting a slit. In this type, because of coupling, the electrical phase of quarter -wavelength line and the performance change. For this reason, with the inductive slit and the tuning of quarter-wavelength line length, we have compensated for those. The inductance value of the inserted slit is decided by its width and depth, therefore, we could improve the electrical performance through optimization of inductance. Input and output return losses of the designed power divider were -34.2 dB, -34.3 dB respectively, and isolation was -36.7 dB at 1.75 GHz. Besides, a new design approach reduced occupied substrate area by 3:1 approximately.