• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.512-514
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• 2007

The number of transformers and the size of transformers in inverter using 3-phase transformer could be reduced compare with a multi-level inverter using single phase transformer. but still the 3-phase transformer inverter needs many switches. In this study, we proposed the isolated multi-level inverter using 3-phase transformers and common arm. Also, the equal-area method is used to calculate conduction angle with switching frequency equal to output fundamental frequency and it can reduce harmonics component of output voltage and switching loss. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1134-1135
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• 2007

In this paper, we proposed the isolated multi-level inverter using 3-phase transformers. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformer could be reduced comparing with an exiting 3-phase multi-level inverter using single phase transformer. Also, using phase angle control method with switching frequency equal to output fundamental frequency, harmonics component of output voltage and switching losses can be reduced. Finally, we made a prototype inverter to clarify the proposed electric circuit and reasonableness of control signal.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.275-282
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• 2008

This paper presents numerical investigation of multi-phase flow in solid rocket motor nozzle and effect of multi-phases on the performance prediction of the Solid Rocket Motor. Aluminized propellants are frequently used in solid rocket motors to increase specific impulse. An Eulerian-Lagrangian description has been used to analyze the motion of the micrometer sized and discrete phase that consist of the larger particulates present in the Solid Rocket Motor. Uniform particles diameters and Rosin-Rammler diameter distribution method has been used for the simulation of different burning of aluminum droplets generating aluminum oxide smokes. Roe-FDS scheme has been used to simulate the effects of the multi-phase flow. The results obtained show the sensitivity of this distribution to the nozzle flow dynamics, primarily at the nozzle inlet and exit. The analysis also provides effect of two phases on performance prediction of Solid Rocket Motor.

• 한국정보통신학회논문지
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• 제14권12호
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• pp.2615-2621
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• 2010

본 논문에서는 메타물질 구조 다중대역 6단자 위상상관기를 설계하고 제작하였다. 이중 주파수 대역에서 신호를 수신 처리할 수 있는 집중소자형 메타물질 구조를 해석하고, 해석된 결과를 기반으로 다중대역 직접변환 수신 전처리기에 적합한 소형화 메타물질 구조 6단자 위상상관기를 제안하고 구현하였다. 다중대역 6단자 위상상관기를 구성하는 저항성 전력 분배기와 메타물질 $90^{\circ}$ 하이브리드 결합기의 산란 계수를 기반으로 동일한 특성을 갖는 6단자 위상상관기 구성 요소를 제작하고 측정하였다. 측정된 메타물질 구조 6단자 위상상관기는 모의실험 결과와 일치하였으며, 이중 주파수 대역에서 -20 dB 이하의 정합과 1 dB 이내의 전달 이득차, 그리고 ${\pm}4.1^{\circ}$ 이하의 전달 위상차 특성으로 양호한 다중대역 6단자 위상상관기 성능을 나타내었다.

• 건축역사연구
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• 제24권3호
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• pp.17-29
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• 2015

This study is about the change of multi-storied buildings in Hanyang, the capital city of Joseon Dynasty. The changes are divided into 3 phases in the viewpoint of architectural types and building types. The first phase is from the early Joseon Dynasty to the time of Japanese invasion to Korea and Sungryemun remains until now. The second phase is from 1592 to the the first half of the 18th century. Many multi-storied Buddhist halls were rebuilt at that time. In the final phase, many multi-storied gate buildings and multi-storied main buildings of palaces were rebuilt. And there are differences between the Buddhist buildings and the main buildings of palaces. By the way the change that architectural style of the Buddhist buildings and the main buildings of pal were switched and mixed occurred. For example, Anguksa Daeungjeon adopted the style of multi-storied gates and Injeongjeon adopted the style of multi-storied Buddhist halls. These phenomenon was result from periodical situation the monk carpenter and his disciple took part in governmental construction like Janganmun.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.95-102
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• 2014

This paper proposes a coordinated control for an independent multi-phase transverse flux linear synchronous motor (IM-TFLSM) based on magnetic levitation. The stator structures of the IM-TFLSM are composed of a two set, which has independent three-phase windings and a double-sided air-gap as opposed to the conventional Y-connected three-phase linear motors. A suitable control algorithm is necessary to operate the applied linear machine. This study proposes a coordinated control algorithm for adjusting the mover air-gap and thrust force of the IM-TFLSM in order to maintain air-gap and phase shifted current control of the independent 3-phase modules. In addition, the principle of operation and its special structures are described in detail and the validity and effectiveness of the control algorithm is verified through multiple experimental results.

• Journal of Communications and Networks
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• 제13권1호
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• pp.43-49
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• 2011

In this paper, a new medium access control (MAC) protocol entitled three-phase multiple access with continual contention resolution (TPMA-CCR) is proposed for wireless multi-hop ad hoc networks. This work is motivated by the previously known three-phase multiple access (TPMA) scheme of Hou and Tsai [2] which is the suitable MAC protocol for clustering multi-hop ad hoc networks owing to its beneficial attributes such as easy collision detectible, anonymous acknowledgment (ACK), and simple signaling format for the broadcast-natured networks. The new TPMA-CCR is designed to let all contending nodes participate in contentions for a medium access more aggressively than the original TPMA and with continual resolving procedures as well. Through the systematical performance analysis of the suggested protocol, it is also shown that the maximum throughput of the new protocol is not only superior to the original TPMA, but also improves on the conventional slotted carrier sense multiple access (CSMA) under certain circumstances. Thus, in terms of performance, TPMA-CCR can provide an attractive alternative to other contention-based MAC protocols for multi-hop ad hoc networks.

• 전기학회논문지
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• 제56권6호
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• pp.1071-1079
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• 2007

In this paper, a novel space vector control method for isolated multi-level inverter using 3-phase low frequency transformers is proposed. This method is based on the simplification of the space-vector diagram of a five-level inverter using calculated table into fully programming method. The execution time of the proposed method is about same as that of the method using calculated table. Also, the proposed method is easily applied to other case level inverter. We applied this method into the 3-phase IHCML inverter using common arm. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformers could be reduced compare with an exiting 3-phase multi-level inverter using single phase transformer. In addition, this method generates very low harmonic distortion operation with nearly fundamental switching frequency. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• 전기학회논문지
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• 제65권4호
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• pp.576-585
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• 2016

The current control methods of Y-connected 7 Phase BLDC motor are sine wave current control and square wave control. The sine wave current control method needs dq axis transformation of $7{\times}7$ matrix for current control and very complex. Also this method is not suitable for multi Phase BLDC motor of trapezoidal back emf wave. Therefore, in Y connected multi phase BLDC motor, the square wave current control methods are required. Generally, in the 3Phase BLDC system, Average current control method is used for current control. The average current is obtained that the summation of absolute value of each phase current magnitude is divided by the number of conduction phase. However, if average current control method is applied to multi-phase system, there is a problem that each phase currents are different. This problem affects unbalance of each phase torque and fluctuation of total torque. This paper proposed each phase current control method of Y connected 7Phase BLDC system. Proposed method is used for PI controller of each phase for each phase current control. This method can perfect square wave current control. Also, configuration of the method is easier than DQ axis transformation. Proposed method is verified through simulation and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.718-720
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• 1999

This paper describes a charge pump PLL architecture which achieves high frequency operation and fast acquisition. This architecture employs multi-phase frequency detector comprised of precharge type phase frequency detector and conventional phase frequency detector. Operation frequency is increased by using precharge type phase frequency detector when the phase difference is small and acquisition time is shortened by using conventional phase frequency detector and increased charge pump current when the phase difference is large. By virtue of this multi-phase frequency detector structure, the maximum operating frequency of 694MHz at 3.0V and faster acquisition were achieved by simulation.