• 전기학회논문지
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• 제57권3호
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• pp.375-383
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• 2008

This paper deals with reduction and analysis of cogging torque for permanent magnet synchronous generators with multi-pole rotor for wind power applications. Open-circuit field solutions are derived using a magnetic vector potential and a two-dimensional (2-d) polar coordinate systems. On the basis of derived open-circuit field solutions and 2-d permeance functions, we also derive open-circuit field solutions considering stator slotting effects. By using open-circuit field solutions considering stator slotting effects and energy variation methods, this paper analytically predicts the cogging torque considering skew effects. All analytical results are shown in good agreement with those obtained from finite element (FE) analyses. In order to reduce the cogging torque, by predicting the variation of the cogging torque according to pole arc/pitch ratio using analytical and FE methods, pole arc/pitch ratio which makes the cogging torque minimum are determined. However, we confirm that measured value for cogging torque of the PMG with determined pole arc/pitch ratio is twice higher than predicted value. Therefore, the reason for an error between measured and predicted cogging torque is discussed in terms of a shape of PMs and is proved experimentally.

• The Journal of the Acoustical Society of Korea
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• 제14권2E호
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• pp.43-49
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• 1995

인공지능(AI)의 한기법인 Space Search 기법을 이용하여 회로의 단선 결함의 유무 및 결함위치를 찾아내는 방법을 제시하였다. 보통 회로의 결함은 단선 및 단락의 구조적 결함으로 나뉘어진다. 두가지 결함 모두 회로의 기능에 중대한 이상을 초래한다. 그중 단선에 의한 회로의 결함에 대하여 다루었다. 우선 회로를 net와 net의 연결 path에 따라 tree 구조로 변환하였다. 서로 독립된 net들은 서로 다른 tree의 node를 이루며 각각의 tree는 적기적으로 연결됨이 없다. 각 tree의 최상단부의 root node에 test vector를 입력하고 최하단부의 leaf node에서 vector를 관찰하여 입력된 test vector와 비교한다. 그 비교 결과 동일 유무에 따라 결함의 유무를 판정한다. 결함이 있다고 판정된 leaf node는 depth search 방법에 의하여 root node쪽으로 test vector를 관찰하여, 전기적 신호에 의하여 회로의 서놔 단선된 위치를 찾아내도록 하는 방법을 제시하였다.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.1002-1006
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• 2010

In this study, magnesium (Mg), zinc (Zn) and aluminium (Al) as anode electrode and the solution of NaCl dissolved with 2~20 wt% as electrolytes were used for the metal-air cell. The open circuit voltage, short circuit current and I-V characteristics upon different kinds of anode electrode and electrolyte concentration were investigated. The open circuit voltage, initially about 1.45 V, rises to 1.6 V during the first 10 minutes indicating the necessity of an induction time to activate the catalyst on the air cathode. The short circuit current increases with an increased concentration of NaCl, causes an increase in the conductivity of the electrolyte solution, but the open circuit voltage did not under undergo influence of electrolyte. From NaCl 20 wt% electrolyte, the maximum output power of the magnesium electrode materials was measured with 177mW. It is found that the power characteristics of metal-air cell could be improved by using magnesium electrode materials in the NaCl electrolyte.

• 한국초전도ㆍ저온공학회논문지
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• 제3권2호
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• pp.32-38
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• 2001

A 30[kVA] superconducting generator (SCG) is built and tested at Korea Electrotechnology Research Institute (KERI) in Korea. This superconducting generator has an air-gap winding instead of the typical steel teeth structure. The rotor has 4 field coils of race-track type with NbTi superconducting wired. The rotor is composed of two dampers and a liquid helium composed of two dampers and a liquid helium container in which the field poles reside. The space between the outermost damper and the container is vacuum insulated. A ferrofluid seal is used between the stationary part connected to the couping and the rotor. A helium transfer coupling(HTC) has 3 passages of the recovered heilum gas and a gas flow control system. The open circuit test and sustained short circuit test are preformed to obtain the open circuit characteristics (OCC) and short circuit characteristics (SCC) Also. the test results usder the light load (up to 3.6[kW]) are given. The structure, manufacturing and basis test of the 30[kVA]SCG are discussed.

• Journal of electromagnetic engineering and science
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• 제16권3호
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• pp.169-181
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• 2016

This work presents a new method for enhancing the performance of a dual band Planer Inverted-F Antenna (PIFA) and its lumped equivalent circuit formulation. The performance of a PIFA in terms of return loss, bandwidth, gain, and efficiency is improved with the addition of the proposed open stub in the radiating element of the PIFA without disturbing the operating resonance frequencies of the antenna. In specific cases, various simulated and fabricated PIFA models illustrate that the return loss, bandwidth, gain, and efficiency values of antennas with longer optimum open stub lengths can be enhanced up to 4.6 dB, 17%, 1.8 dBi, and 12.4% respectively, when compared with models that do not have open stubs. The proposed open stub is small and does not interfere with the surrounding active modules; therefore, this method is extremely attractive from a practical implementation point of view. The second presented work is a simple procedure for the development of a lumped equivalent circuit model of a dual band PIFA using the rational approximation of its frequency domain response. In this method, the PIFA's measured frequency response is approximated to a rational function using a vector fitting technique and then electrical circuit parameters are extracted from it. The measured results show good agreement with the electrical circuit results. A correlation study between circuit elements and physical open stub lengths in various antenna models is also discussed in detail; this information could be useful for the enhancement of the performance of a PIFA as well as for its systematic design. The computed radiated power obtained using the electrical model is in agreement with the radiated power results obtained through the full wave electromagnetic simulations of the antenna models. The presented approach offers the advantage of saving computation time for full wave EM simulations. In addition, the electrical circuit depicting almost perfect characteristics for return loss and radiated power can be shared with antenna users without sharing the actual antenna structure in cases involving confidentiality limitations.

• 대한전기학회논문지
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• 제36권5호
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• pp.339-345
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• 1987

In the region of high temperature, a very appreciable short-circuit current Is was observed from M1(A1)-P(PET)-M2(Cu) system sandwitched with hetero metals without applying external field. The short-circuit current Is is greatly dependent on electrode material and it has been certified by measuring open-circuit voltage. From these experimental results, we can see that Is is due to electro-chemical action in M-P interface. In this electro-chemical reaction,the generation reaction and the solution reacftion of the oxidies from electrode are probably co-exist and the measured values of the open-circuit voltage was almost correspond to those calculated from Nernst equation.

• 정보과학회지
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• 제30권5호
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• pp.42-47
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• 2012

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.149-156
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• 2019

5쌍의 Bi₂Te₃계 p-n 가압소결체 열전레그들로 구성되어 있으며 상하부 기판이 없고 내부는 polydimethylsiloxane (PDMS)로 충진되어 있는 신축열전모듈을 형성하고, 이의 신축특성과 발전특성을 분석하였다. 신축열전모듈에 변형률 0~0.1 범위의 신축변형 싸이클을 10회 인가하여도 모듈의 integrity가 잘 유지되었으며, 인장변형률이 0.2로 증가시 Cu 전극과 열전레그 사이의 접합부 파단에 의해 모듈이 open 되었다. 신축열전모듈은 열전레그 양단간의 온도차가 2.2 K일 때 4.6 mV의 open circuit 전압을 나타내었으며, 변형률 0~0.1 범위의 인장변형에 의한 open circuit 전압의 변화는 5% 미만이었다. 신축열전모듈은 0.1의 변형률로 인장된 상태에서 레그 양단간 온도차 2.2 K에 의해 18.5 ㎼의 최대발전출력을 나타내었다.

• 설비공학논문집
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• 제22권5호
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• pp.259-267
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• 2010

An experiment has been performed in order to investigate the characteristics of multiple thermoelectric modules (TEMs) with electrical circuits. The open circuit voltage of TEM connected parallel circuit is equal to the sum of individual TEMs. In contrast, the open circuit voltage is equal to the average of that individual TEM for a series circuit. The power output and conversion efficiency of TEM for both parallel and series circuits increase as the operating temperature conditions for individual TEMs becomes identical. Comparing parallel with series circuits, the power generation performance is more excellent for series circuit than parallel circuit. This result is attributed to the power loss from the TEM with better power generation performance.

• 전력전자학회논문지
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• 제18권3호
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• pp.217-224
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• 2013

This paper presents a diagnostic method for a sparse matrix converter that detects faults in any single switch or a pair of switches. The sparse matrix converter is functionally equivalent to the standard matrix converter but has a reduced number of switches. The proposed diagnostic method is based in the measurement of input and output currents. The currents have respective characteristic according to the location of faulty switches. This method not only detects the switches of open-circuit fault but identifies the location of the faulty switching devices without complicated calculations. The simulation and experimental results verify that, based on the proposed method, the fault of sparse matrix converter can be easily and fast detected.