• Journal of Advanced Navigation Technology
• /
• v.26 no.3
• /
• pp.160-165
• /
• 2022

In this paper, we have proposed a magnetic resonant 6.78MHz WPT(wireless power transfer) technique which can be applied to a fixed transmitter and a receiver of varying relative distance and coil alignment, Power transmission characteristics are studied with the relative distance and misalignment ration of coil area between the transmitting and receiving coils. The coils are designed with the size of 60×80mm² by direct feeding method, and the characteristics are derived with the maximum relative distance of 50mm and horizontal area misalignment state of 0-40mm misalignment of coil center axis in the XY plane. The power transmission characteristics are compared between the 3D EM simulation and the measured data, and the power transmission shows larger than -3dB performance with the vertical distance of up to 30mm and 50% area misalignmment ratio. This work showsthe transmission characteristics according to relative distance and misalignment state between the cols and that direct feeding has advantage for the short relative distance and small misalignment ratio.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.6
• /
• pp.650-657
• /
• 2001

This paper explains the process of designing a shielded encircling remote field eddy current (RFEC) probe to inspect nuclear fuel cladding tubes and investigates resulting signal characteristics. To force electromagnetic energy from exciter coil to penetrate into the tube, exciter coil is shielded outside by laminations of iron insulated electrically from each other. Effects of shielding and the proper operating frequency are studied by the finite element analysis and the location for sensor coil is decided. However, numerically simulated signals using the designed probe do not clearly show the defect indication when the sensor passes a defect and the other indication appeared as the exciter passes the defect is affected by the shape of shielding structure, which demonstrates that the sensor is directly affected by exciter fields. For this reason, the sensor is also shielded outside and this shielding dramatically improves signal characteristics. Numerical modeling with the finally designed probe shows very similar signal characteristics to those of inner diameter RFEC probe. That is, phase signals show almost equal sensitivity to inner diameter and outer diameter defects and the linear relationship between phase signal strength and defect depth is observed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.11
• /
• pp.861-869
• /
• 2020

A dynamo set for a high-power induction motor drive is expensive and needs a long time to manufacture. Therefore, the development of a simulator that functions as the induction motor and load equipment is required. A load simulator of an inverter for a high-power three-phase induction motor consists of a reactor and three-phase PWM inverter. Therefore, it cannot simulate the dynamic characteristics of an induction motor and functions only as a load. In this paper, a real-time simulator is proposed to simulate a model of an induction motor and the load characteristics based on an LCL filter and three-phase PWM rectifier for a three-phase induction motor. The currents of a PWM inverter that simulate the stator currents of the motor are controlled by the inductor currents and capacitor voltages of the LCL filter. The capacitor voltages of the LCL filter simulate the induced voltages in the stator windings by the rotating rotor fluxes of the motor, and the capacitor voltages are controlled by the inductor currents and a PWM rectifier. The rotor currents, the stator and rotor flux linkages, the electromagnetic torque, the slip frequency, and the rotor speed are derived from the inverter currents and the motor parameters. The electrical and mechanical model characteristics and the operation of vector control were verified by MATLAB/Simulink simulation.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.11B no.3
• /
• pp.112-118
• /
• 2001

In the near future, the voltage of power system for passenger vehicle will be changed to 42V from existing 14V./ Because of increasing power and voltage ratings used in the vehicle the motor drive system has high switching dv/dt and it generates electromagnetic interference (EMI) To solve these problems multi-level inverter system may be used The feature of multi-level inverter is the output voltage to be synthesized from several levels of voltage Because of this feature high switching dv/dt and EMI can be reduced in the multi-level inverter system But as the number of level is increased manufacturing cost is getting expensive and system size is getting large. Because of these disadvantages the application of multi-level inverter has been restricted only to high power drives. The method to reduce manufacturing cost and system size is to integrate circuit of multi-level inverter into a few chips But isolated power supply and signal isolation circuit using transformer or opto-coupler for drive circuit are obstacles to implement the integrated circuit (IC) In this paper a drive circuit of 4-level inverter suitable for integration to hybrid or one chip is proposed In the proposed drive circuit DC link voltage is used directly as the power source of each gate drive circuit NPN transistors and PNP transistors are used to isolate to transfer the control signals. So the proposed drive circuit needs no transformers and opto-couplers for electrical isolation of drive circuit and is constructed only using components to be implemented on a silicon wafer With th e proposed drive circuit 4- level inverter system will be possible to be implemented through integrated circuit technology Using the proposed drive circuit 4- level inverter system is constructed and the validity and characteristics of the proposed drive circuit are proved through the experiments.

• 전자공학회논문지 IE
• /
• v.43 no.4
• /
• pp.122-127
• /
• 2006

A series of conductive filler were prepared with electroless plating method. Base conductive materials of the filler were nickel and copper. The cores were prepared with Nylon 6 and rayon in different aspect ratio. Also, various complexes were made with ABS resin and conductive filler with different filler feed ratio. The conductivity of the filler was measured with conductivity analyzer and the size distributions of fillers was measured with laser particle size analyzer. Electromagnetic wave shielding efficiency of each complex film was measured with flange circular coaxial transmission line sample holder within the 1MHz$\sim$1GHz bandwidth range. From this study, the conductivity of filers surpass that of other carbon films. It is available that the filler made of fibrous materials can be applied in plastic molding industry of electric appliances as a EMI filler.

• Journal of Power Electronics
• /
• v.15 no.3
• /
• pp.621-633
• /
• 2015

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.2
• /
• pp.153-160
• /
• 2013

An orthotropic magneto-rheological rubber composite (MRRC) based on a general-purpose rubber can be manufactured by using an electromagnetic device during the curing processes of rubber mixtures. The magnetic transmissivity of MRRCs increases with the iron particle (IP) content, and that of aligned MRRCs with a 2-T magnetic field is 1.8 to 2 times higher as compared to that of randomly dispersed MRRCs. The effect of a 2-T magnetic field on carbon nanotube (CNT) reinforced MRRC has been identified clearly, and the magnetic transmissivity is found to be 3.7%. The compressive stress of MRRC (IP 90 + CNT 5, 2 T alignment) under a magnetic field of 0.49 T is 2.1 times higher as compared to that of the matrix. The MR effect of MRRC increases with the IP content, and that of aligned MRRC with the IP 90 and 2 T magnetic field is 20.4%. It is confirmed that the magnetic field when making the specimen and when performing the compression test greatly impacts the compression characteristics.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.185.2-185.2
• /
• 2016

The plasma density is an essential plasma parameter describing plasma physics. Furthermore, it affects the throughput and uniformity of plasma processing (etching, deposition, ashing, etc). Therefore, a novel technique for plasma density measurement has been attracting considerable attention. Microwave probe is a promising diagnostic technique. Various type of cutoff, hairpin, impedance, transmission, and absorption probes have been developed and investigated. Recently, based on the basic type of probes, modified flat probe (curling and multipole probes), have been developing for in situ processing plasma monitoring. There is a need for comparative study between the probes. It can give some hints on choosing the reliable probe and application of the probes. In this presentation, we make attempt of numerical study of different kinds of microwave probes. Characteristics of frequency spectrum from probes were analyzed by using three-dimensional electromagnetic simulation. The plasma density, obtained from the spectrum, was compared with simulation input plasma density. The different microwave probe behavior with changes of plasma density, sheath and pressure were found. To confirm the result experimentally, we performed the comparative experiment between cutoff and hairpin probes. The sheath and collision effects are corrected for each probe. The results were reasonably interpreted based on the above simulation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.9
• /
• pp.1633-1640
• /
• 2016

In this paper, we propose a open-ended rectangular microstirp patch antenna with fork-shaped feeding structure. This antenna extends the effective bandwidth by transforming single or multi resonant frequency and is designed planar monopole structure with microstrip line to satisfy the WLAN bands (2.4 - 2.484, 5.15 - 5.35, 5.25-5.825 GHz). The substrate is printed in 0.8 mm thickness on an FR-4 board. A commercial 3D simulation tool was used to analyze surface current and electromagnetic field distribution in order to analyze the operation mode and reconfiguration principle of antenna. According to the lengths of individual patches, simulated reflection loss was compared to obtain optimized values. When it was designed with the optimized values, it satisfied WLAN bands (2.380 - 2.710, 4.900 - 5.950 GHz), if the switch is off, and 2.4 WLAN band (2.380 - 2.710 GHz). From the fabricated and measured results, measured results of return loss, gain and radiation patterns characteristics displayed for operating bands.

• Journal of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.303-306
• /
• 2005

Transient luminous events (TLEs; sprites, elves, jets and etc.) are lightning-related optical flashes occurring above thunderstorms. Since the first discovery of sprites in 1989, scientists have learned a great deal about the morphological, spectroscopic and electromagnetic characteristics of TLEs through ground and spacecraft campaigns. However, most of the TLE studies were based on events recorded over US High Plains. To elucidate the possible biasing effects, space-borne observations are needed and have their merits. Imager of sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT-2 satellite is the first instrument to carry out a true global measurement of TLEs from a low- earth orbit. In this short paper, we apply a common astronomical data analysis technique, two-color diagram, on the ISUAL spectrophotometer (SP) data. By choosing appropriated bandpasses and converting the measured flux of TLEs into the unit of magnitude, two-color diagrams of TLEs can be constructed. We demonstrate that two-color diagrams, which were constructed from the narrow-band spectrophotometer data, can be used to classify different types of TLEs and trace their temporal evolution. The amount of reddening due to Earth's atmosphere can also be estimated from two-color diagrams assembled from the broad-band spectrophotometer data.