• 제목/요약/키워드: resonance circuit

검색결과 497건 처리시간 0.021초

Analysis of the Bird-cage Receiver Coil of a MRI System Employing a Equivalent Circuit Model Based on a Transmission Matrix (전송행렬 기반 등가 회로 모델을 이용한 자기공명영상 장치용 새장형 수신 코일 해석)

  • Kim, Hyun Deok
    • Journal of Korea Multimedia Society
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    • 제20권7호
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    • pp.1024-1029
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    • 2017
  • A novel analytic solution has been derived for the bird-cage receiver coil of a magnetic resonance imaging (MRI) system, which is widely used in 3-dimensional medical imaging, by transforming the coil into an equivalent circuit model by using a transmission matrix-based circuit analysis. The bird-cage coil composed of N legs is divided into a cell for which input impedance is to be analyzed and the remaining N-1 cells, and then a transmission matrix corresponding to the N-1 cells is converted into a circuit to transform the 3-dimensional bird-cage coil into the 2-dimensional equivalent circuit model, which is suitable to derive the analytic solution for the input impedance. The proposed method derives directly the analytic solution for the input impedance at an arbitrary point of the coil unlike the conventional analytic solution of a bird-cage coil, so that it can be used not only for resonance frequency calculations but also for various coil characteristics analyses. Since the analytic solution agreed well with the results of computational simulations, it can be useful for the impedance matching of a coil and the analysis and the design of a multi-tune bird-cage coil.

Analysis of electric circuit using capacitor for driving linear compressor (콘덴서를 이용한 선형압축기 구동 전기회로 해석)

  • Ko, Jun-Seok;Kim, Hyo-Bong;Park, Seong-Je;Hong, Yong-Ju;Yeom, Han-Kil;Koh, Deuk-Yong
    • Progress in Superconductivity and Cryogenics
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    • 제14권3호
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    • pp.43-47
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    • 2012
  • A linear compressor generates pulsating pressure and oscillating flow in a cryocooler such as Stirling cryocooler and pulse tube refrigerator. It is driven by AC power source and designed to operate at resonance of piston motion. The driving voltage level is determined by electric parameters of resistance, inductance and thrust constant of linear motor. From voltage equation on linear motor, the power factor of driving power is inherently less than 1. The phase difference between voltage and current of supplied power can be zero using capacitor and this can minimize a supply voltage level. Especially, the linear compressor of kW class requires high voltage and thus can cause a difficulty in selecting power supply unit due to limitation of voltage level. The capacitor in driving electric circuit is useful to settle this problem. In this study, the electric circuit of linear compressor is analytically investigated with assumption of mechanical resonance. The electric parameters of commercial linear motor are used in the analysis. The effects of capacitor on driving voltage level and power factor are investigated. From analytic results, it is shown that the voltage level can be mimized with using capacitor in driving electric circuit.

Analysis for Electrical Stress of Power Capacitor (전력용 커패시터의 전기적 스트레스 해석)

  • Kim, Jong-Gyeum;Park, Young-Jeen;Lee, Eun-Woong;Lee, Dong-Ju
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • 제57권4호
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    • pp.370-376
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    • 2008
  • Power capacitors is widely used for power factor correction and component of passive filter in the user power systems. Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current. There are series resonance and parallel resonance when capacitors are applied in the user electrical application. If this harmonic component matches resonance, voltage and current is magnified and has severely an influences on capacitor. This paper purposes a new method for the magnitude of voltage and current by the frequency scan analysis without equivalent circuit for the actual circuit at the resonance condition.

Operating characteristics of a superconducting DC circuit breaker connected to a reactor using PSCAD/EMTDC simulation

  • Kim, Geon-woong;Jeong, Ji-sol;Park, Sang-yong;Choi, Hyo-sang
    • Progress in Superconductivity and Cryogenics
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    • 제23권3호
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    • pp.51-54
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    • 2021
  • The DC system has less power loss compared to the AC system because there is no influence of frequency and dielectric loss. However, the zero-crossing point of the current is not detected in the event of a short circuit fault, and it is difficult to interruption due to the large fault current that occurs during the opening, so the reliability of the DC breaker is required. As a solution to this, an LC resonance DC circuit breaker combined a superconducting element has been proposed. This is a method of limiting the fault current, which rises rapidly in case of a short circuit fault, with the quench resistance of the superconducting element, and interruption the fault current passing through the zero-crossing point through LC resonance. The superconducting current limiting element combined to the DC circuit breaker plays an important role in reducing the electrical burden of the circuit breaker. However, at the beginning of a short circuit fault, superconducting devices also have a large electrical burden due to large fault currents, which can destroy the element. In this paper, the reactor is connected to the source side of the circuit using PSCAD/EMTDC. After that, the change of the fault current according to the reactor capacity and the electrical burden of the superconducting element were confirmed through simulation. As a result, it was confirmed that the interruption time was delayed as the capacity of the reactor connected to the source side increased, but peak of the fault current decreased, the zero-crossing point generation time was shortened, and the electrical burden of the superconducting element decreased.

A 90°-Bent Spur-Line Combined CRLH ZOR Bandpass Filter for the Channel of the UWB Communication System

  • Lee, Changhyeong;Kahng, Sungtek
    • Journal of Electrical Engineering and Technology
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    • 제13권2호
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    • pp.928-935
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    • 2018
  • In this paper, a compact fully printable bandpass filter is suggested for a low-frequency channel 3.2 GHz ~ 3.7 GHz in the Ultra-Wideband (UWB) communication system. It is featured with a small geometry of $0.5{\lambda}_g/15$ and a low insertion loss despite using FR4 as a cheap substrate of a high dielectric loss. This is made possible by generating zeroth-order-resonance (ZOR) from one cell comprising two series resonances obviously separated from one shunt resonance as a third-order bandpass filter. Especially, the series resonance elements are combined with spur-lines bent by 90 degrees, which makes the port-impedance matched well and eliminates spurious hikes in the stopband, while the overall size remains almost unchanged. The design is carried out by setting up the equivalent circuit and the circuit simulation is checked by the full-wave EM analysis. The structure is manufactured and measured to show that the circuit modeling and EM simulation results agree with the measured data.

Reduction of Electromagnetic Field from Wireless Power Transfer Using a Series-Parallel Resonance Circuit Topology

  • Kim, Jong-Hoon;Kim, Hong-Seok;Kim, In-Myoung;Kim, Young-Il;Ahn, Seung-Young;Kim, Ji-Seong;Kim, Joung-Ho
    • Journal of electromagnetic engineering and science
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    • 제11권3호
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    • pp.166-173
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    • 2011
  • In this paper, we implemented and analyzed a wireless power transfer (WPT) system with a CSPR topology. CSPR refers to constant current source, series resonance circuit topology of a transmitting coil, parallel resonance circuit topology of a receiving coil, and pure resistive loading. The transmitting coil is coupled by a magnetic field to the receiving coil without wire. Although the electromotive force (emf) is small (about 4.5V), the voltage on load resistor is 148V, because a parallel resonance scheme was adopted for the receiving coil. The implemented WPT system is designed to be able to transfer up to 1 kW power and can operate a LED TV. Before the implementation, the EMF reduction mechanism based on the use of ferrite and a metal shield box was confirmed by an EM simulation and we found that the EMF can be suppressed dramatically by using this shield. The operating frequency of the implemented WPT system is 30.7kHz and the air gap between two coils is 150mm. The power transferred to the load resistor is 147W and the real power transfer efficiency is 66.4 %.

A Study on the Efficiency of LED Lighting Applied by Direct AC Power Using Magnetic Resonance Wireless Power Transfer System (자계 공진 방식의 무선전력전송 장치를 이용한 교류 전력 직접 인가에 의한 LED 조명기기 효율에 관한 연구)

  • Park, Jeong-Heum
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • 제27권10호
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    • pp.15-20
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    • 2013
  • In this paper, wireless power transfer system using the magnetic resonance was designed and applied to LED lighting for implementation of wireless lighting. This lighting was made by the converted DC driving type and the direct AC driving type. In the former, transferred AC power was rectified into DC and regulated to the specified voltage value, which leads to produce the loss at the rectifying and regulating circuit. In the latter, wireless-transferred AC power was directly applied to LED, which get rid of the loss derived from the additional circuit. For the efficiency-comparison between the former and the latter, the power at each stage was measured when the same optical output radiated from LED lighting part. The result revealed that the direct AC driving type had 18% higher efficiency than the DC driving type and confirmed that LED lighting using magnetic resonance wireless power transfer system can be efficient by direct AC power supply. And the direct AC driving type had the simple circuit structure and the simple LED lighting formation, so this can leads to various application.

High-Power Electronic Ballast Design for Metal-Halide Lamp without Acoustic Resonance (음향 공명 현상을 제거한 MHL용 고출력 전자식 안정기 설계)

  • Park, Chong-Yun;Kim, Ki-Nam;Lee, Bong-Jin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • 제57권7호
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    • pp.1187-1194
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    • 2008
  • This paper presents a high-power electronic ballast for a metal-hallide lamp(MHL) that employs frequency modulation(FM) technique to eliminate acoustic resonance(AR). The proposed ballast consists of a full-bridge rectifier, a power factor correction(PFC) circuit, a full-bridge(FB) inverter, an ignitor using LC resonance and an FM control circuit. Whereas a manual PFC provides advantages in terms of high reliability and low cost for constructing the circuit, it is difficult to supply a stable voltage because of the output voltage ripple that occurs with a period of 120Hz. Although the ballast can be designed with a small size and a light weight if it is driven at a switching frequency between 1 and 100 kHz, AR will occur if the eigen-value frequency of the lamp coincides with the inverter's operation frequency. The operation frequency was modulated in real time according to the output voltage ripple to compensate for the variation in power supplied to the lamp and eliminate AR. Performance of the proposed technique was validated through numerical analysis, computer simulation using PSPICE and by applying it to an electronic ballast for a prototype 1kW MHL.

Electrical Properties of a Laminated Piezoelectric Transformer with the Divided Electrodes (전극 분할 적층형 압전변압기의 전기적 특성)

  • Lee, Yong-Kuk;Lee, Sang-Cheal;Hur, Doo-Oh;Han, Deuk-Young
    • Proceedings of the KIEE Conference
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    • 대한전기학회 1995년도 하계학술대회 논문집 C
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    • pp.1140-1142
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    • 1995
  • The transformer is fabricated with two piezoelectric vibrator with the divided electrodes and adhesive insulator. We applied the electric input to the driving vibrator in parallel and connect the output voltage to the generating vibrator in series to the resistor load near its fundamental resonance frequency. Then we investigate output voltage in series twice as large as in parallal. Moreover we investigate the load characteristics at resonance frequencies under various resistor and the frequency characteristics near the resonance frequency under no load. Its equvalent circuit is derived from the Mason's model of a thickness-driven piezelectric vibrator. By its equevalent circuit, symbolic expressions for input impedances, voltage ratios, resonance frequencies, and bandwidths have been derived. The values calculated from those symbolic exprssions are shown to agree well with the measurement values.

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A Telemetry Silicon Pressure Sensor of LC Resonance Type (LC공진을 이용한 원격측정용 압력센서의 제작 및 실험)

  • Kim, Hak-Jin;Kim, Soon-Young;Yang, Sang-Sik
    • Proceedings of the KIEE Conference
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    • 대한전기학회 2001년도 하계학술대회 논문집 C
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    • pp.1872-1874
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    • 2001
  • This paper presents an implantable telemetry LC resonance-type pressure sensor to measure the cerebral ventricle pressure. The sensor consists of an inductor and a capacitor. The LC resonant circuit consists of the sensor and an external antenna coil that are coupled magnetically. The resonance frequency of the circuit decreases as the applied pressure increases the capacitance of the sensor. The sensor is designed in consideration of the biocompatibility and long lifetime for continuous monitoring of the ventricle pressure. The sensor is simple to fabricate and small in comparison with others reported previously. The inductor is fabricated by electroplating and the variable capacitor is constructed with a flexible p+ diaphragm. Also, the deflection of the diaphragm, the variation of the capacitance and the resonance frequency are analyzed and calculated.

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