• 전자공학회논문지
• /
• 제50권1호
• /
• pp.174-179
• /
• 2013

이 논문에서는 multiple split ring resonator(MSRRs)와 로딩된 스위치드 제어부를 이용하여 2개의 전송영점을 가지는 대역통과 여파기를 설계하였다. 높은 선택도와 칩 사이즈의 초소형화를 위해 비대칭의 급전 선로를 도입하여 통과 대역 주위에 위치한 전송 영점 쌍을 생성하였다. Cross coupling 또는 source-load coupling 방식을 이용한 기존의 여파기와 비교해보면 이 논문에서 제안된 여파기는 단지 2개의 공진기만으로 전송 영점을 생성하여 높은 선택도를 얻었다. 여파기의 선택도와 민감도(삽입 손실)를 최적화하기 위해 비대칭 급전 선로의 위치에 따른 전송 영점과 삽입손실의 관계를 분석하였다. 통과 대역 주파수의 가변과 30dBm 정도의 고 출력 신호를 처리하기 위해 MSRRs의 최 외각 링에 MIM 커패시터와 stacked-FET으로 구성된 SOI-CMOS 스위치드 제어부가 로딩되어 있다. 스위칭 트랜지스터의 전원을 켜고 끔으로써 통과 대역 주파수를 4GHz로부터 5GHz까지 이동시킬 수 있다. 제안된 칩 여파기는 0.18-${\mu}m$ SOI CMOS 기술을 이용함으로써 높은 Q를 가지는 수동 소자와 stacked-FET의 집적을 가능하게 만들었다. 설계된 여파기는 $4mm{\times}2mm$ ($0.177{\lambda}g{\times}0.088{\lambda}g$)의 초소형화 된 크기를 가진다. 여기서 ${\lambda}g$는 중심 주파수에서의 $50{\Omega}$ 마이크로스트립 선로의 관내 파장을 나타낸다. 측정된 삽입손실(S21)은 5.4GHz, 4.5GHz에서 각 각 5.1dB, 6.9dB를 나타내었다. 설계된 여파기는 중심 주파수로부터 500MHz의 오프셋에서 20dB이상의 대역외 저지 특성을 나타내었다.

• Journal of Power Electronics
• /
• 제18권5호
• /
• pp.1315-1324
• /
• 2018

A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.

• 한국전자파학회논문지
• /
• 제17권11호
• /
• pp.1132-1142
• /
• 2006

본 연구는 송전 선로 여러 가지 유형의 극저주파 자기장 저감 적용 모델을 조사하고 그 효과를 분석하였다. 본 연구에서는 154 kV 수평 배열 송전 선로를 기본으로 하여 적용 가능한 다양한 자기장 저감 모델에 대하여 적용시 얻게 되는 자기장 저감지수(Field Reduction Factor)를 검토하였다. 그 결과 compact 모델 채용시에는 상간거리 compact화 비율과 자기장 저감지수가 거의 비례하였으며, diamond 모델 및 transposed 선로 배치의 경우는 50 %에 근접한 자기장 저감이 가능하였다. 배전 선로에 적용이 가능한 삼각형 배열은 33 % 정도, 2회선 split는 50 % 정도 저감 효과가 나타나는 것으로 분석되었으며 수평 multi split 모델의 경우는 80 %까지 자기장 저감을 얻을 수 있었다.

• 전기의세계
• /
• 제18권5호
• /
• pp.20-25
• /
• 1969

The development of the frequency convertors using semiconductors devices makes it possible to control the speed of A.C. motors easily. It is now economically feasible to provide them with power at adjustable frequency using silicon-controlled rectifier (or thyristor) inverters. In such a case, in order to operate an induction motor efficiently over a wide speed range, it must be supplied from a variable frequency source of which frequency is adjustable over the speed range of the motor. It is desired to observe the changes in characteristics as primary current, torque-speed of induction motor etc. at any optional frequency. Although the characteristics can be obtained by means of the conventional methods, they require very complicated precedures of calculations. The Current Diagram Method in this paper suggests a new approach to simpler calculations of the characteristics, using the motor constants at reference frequency. The conclusions of this study are summarized as follows: 1) The equations of stator current at adjusted frequency were derived to construct graphical chart and the current circle required for the Current Diagram Method. 2) The radius, center of the current circle and the vector locus, the basis for calculating the characteristics, at any desired frequency could be easily determined with the aid of both the derived graphical chart and current circle at reference frequency. 3) The method was shown to be applicable to the various types of 3-phase induction motors and also dealt with its application to the split-phase, condenser motors.

• 전기의세계
• /
• 제17권3호
• /
• pp.29-38
• /
• 1968

The development of the frequency converter using semiconductor enables to easily control the speed of A.C. motors. It is now technically possible and economically feasible to provide them with power at variable frequency, using silicon-controlled-rectifier (or thyristor) inverters. In such a case, if an induction motor is to be operated efficiently over a wide speed range, it must be supplied from a variable-frequency source whose frequency is adjustable over a range similar to that required for the motor speed. It is desired to observe how several characteristics are changed such as primary current, torque-speed, etc. Although the characteristics could be obtained by means of the conventional method, it requires very complicated calculation. It is assumed that the charateristics above are easily investigated by means of current diagram method from variable circuit constants relating to the motor which is designed in rated frequency. In this paper, the results of the study on the current-diagram method and its application are described as follows; (1) In order to discuss the construction of current diagram, the equation of the stator current with adjustable frequency was derived for applying the Current Diagram Method. (2) The radius, the center of the current circle and current vector locus at any desired frequency could be easily determined with the aid of both above mentioned equation and the standard current diagram at reference frequency. (3) This method could be applicable to the various types of Induction Motors, and this paper has dealt with its application to the capacitor, split-phase and 2-phase types of motors.

• 전기의세계
• /
• 제18권4호
• /
• pp.22-30
• /
• 1969

The development of the frequency convertors using semiconductors devices makes it possible to control the speed of A.C. motors easily. It is now economically feasible to provide them with power at adjustble frequency using silicon-controlled rectifier (or thyristor) inverters. In such a case, in order to operate an induction motor efficiently over a wide speed range, it must be supplied from a variable frecuency source of which frequency is adjustable over the speep range of the motor. It is desired to observe the changes in characteristics as primary current, torque-speed of induction moter etc. at any optional frequncy. Although the charactheristies can be obtained by means of the conventional methods they require very complicated precedures of calcuations. The Current Diagram Method in this paper suggests a new approach to simpler calcuations of the characteristics, using the motor constants at reference frequency. The conclusions of this study are summarized as follows: (1) The equations of stator current at adjusted frequency were derived to construct graphical chart and the current circle required for the Current Diagrm Method. (2) The radius, center of the current circle and the vector locus, the basis for calculating the characteristics, at any desired frequency could be easily determined with the aid of both the derived graphical chart and current circle at reference frequency. (3) The method was shown to be applicable to the various types of 3-phase induction motors and also dealt with its application to the split-phase, condenser motors.

• Asian-Australasian Journal of Animal Sciences
• /
• 제13권5호
• /
• pp.630-635
• /
• 2000

Previous research has not evaluated the effects of various rates and frequencies of manure application and frequencies of cutting on yield and stand persistence of cool-season grasses and alfalfa-grass mixtures. The primary objective of this study was to compare the effects of cutting management systems on herbage yield and stand persistence of orchardgrass (Dactylis glomerata L.) and an alfalfa (Medicago sativa L.)-orchardgrass mixture from various rates and frequencies of dairy slurry application. A randomized complete block design with treatments in a sub-subplot arrangement with four replicates was used. The main plot consisted of 2 cutting management systems (4 and 5 annual cuttings). The subplots were 9 fertility treatments: 7 slurry rate and frequency of application treatments, one inorganic fertilizer treatment, and an unfertilized control. The split-split-plots were the two forage species: orchardgrass and alfalfa-orchardgrass mixture. The study was initiated after 1st cutting in 1995. Cumulative yields of the 2nd and subsequent cuttings of both orchardgrass and alfalfa-orchardgrass in 1995 were higher for the 5-cutting system than the 4-cutting system. The 1995 growing season was abnormally dry. In 1996, an abnormally wet year, the reverse was true, total herbage yields being higher for the 4-cutting system than the 5-cutting system. Species response to fertility rate/frequency treatments was different in both years. Higher application rates early in the season and carryover of nutrients from late season applications the previous year appear to be responsible for the yield increases of those fertility treatments having significant yield differences between the cutting management systems. The stand ratings of orchardgrass were not affected by cutting management. In the spring of 1997, however, the stand ratings of alfalfa-orchardgrass in the 4-cutting management system were significantly greater than the 5-cutting management system. The very high manure application rate significantly reduced the stand ratings of alfalfa-orchardgrass in the 5-cutting system.

• 전기전자학회논문지
• /
• 제22권2호
• /
• pp.480-483
• /
• 2018

Wireless power transfer (WPT) is the technology that forces the power to transmit electromagnetic field to an electrical load through an air gap without interconnecting wires. This technology is widely used for the applications from low power smartphone to high power electric railroad. In this paper, the model of wireless power transfer circuit for the low power system is designed for a resonant frequency of 13.45 MHz. Also, a feedback WPT circuit to improve the power transfer efficiency is proposed and shown better performance than the original open WPT circuit, and the methodology for power efficiency improvement is studied as the coupling coefficient increases above 0.01, at which the split frequency is made.

• 한국초전도ㆍ저온공학회논문지
• /
• 제6권2호
• /
• pp.35-39
• /
• 2004

The split-type free displacer Stirling refrigerators have been widely used for the cooling of infrared sensors and HTS filters. The thermodynamic and electric performance of the Stirling refrigerator is depending on the design and operating parameters. In the Stirling refrigerator with a free displacer, the refrigeration power is a function of the pressure wave in the expansion space, dynamics of a displacer, driving frequency, and etc.. In this study, the analysis of the small Stirling refrigerator was performed to investigate the effects of design parameters on the cooling capacity. The results show the effects of charging pressure, driving frequency, cold end temperature, natural frequency of a displacer and volume of expansion space on the performance of the Stirling refrigerator.

• Journal of electromagnetic engineering and science
• /
• 제10권4호
• /
• pp.219-223
• /
• 2010

Based on a provided closed-form wireless power transmission (WPT) efficiency formula, which may be used for any value of load, we have analyzed the WPT efficiencies between two metamaterial-inspired loop antennas in various aspects. Due to the modeling based on low frequency circuit theory, the provided formula at the center resonant frequency has been found to be accurate until when the distance between the two loop antennas increases to 15 cm (about $\lambda_0/6$ at 300 MHz). When the two loops get closer, the resonant frequency has been found to split into two in theory, simulations, and measurements. The EM-simulated and measured efficiencies at new resonant frequencies are 60.9 % and 46.3 %, respectively, at d=15 cm. With two extra rings around the loops, the maximum efficiency is enhanced to 93.7 % at d=15 cm. The effect of the additional two rings is about 30 %.