• Title/Summary/Keyword: loss frequency

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Dielectric loss of silicone oils for insulation due to the increase of viscosity (점도증가에 따른 절연용 실리콘유의 유전손실)

  • 이용우;조경순;김왕곤;홍진웅
    • Electrical & Electronic Materials
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    • v.8 no.5
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    • pp.587-593
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    • 1995
  • Silicone oils used insulating substances exhibit the both of organic and inorganic properties, and it has many superior characteristics such as the high thermal resistance and low thermal oxidation level when compared to other insulation oils. In order to investigate the dielectric loss due to the increase of viscosity, silicone oils of viscosity 1, 2, 5[cSt] had been chosen as the specimen and experiment has been performed in the temperature range of -70[.deg. C] - 65[.deg. C] and frequency range of 30 - 1*10$\^$5/[Hz]. As a result, the linear decrease of loss at low frequency region in high temperature was due to the influence of applying frequency, whereas the increase of loss at high frequency region was contributed by electrode's resistance. And increasing viscosity, the activation energy increased from 3.77[kcal/mole] to 7.21[kcal/mole]. The dipole moment of specimen was become clear 1.48 - 2.26[debyel in high temperature region(5 - 65[.deg. C]) and 1.05 - 1.80[debye] in low temperature region (-70 - -25[.deg. C])respectively.

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A Study of Korean Non-linear Fitting Formula based on NAL-NL1 for Digital Hearing Aids (디지털 보청기에서의 NAL-NL1 기반 한국형 비선형 fitting formula 연구)

  • Kim, H.M.;Lee, S.M.
    • Journal of Biomedical Engineering Research
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    • v.30 no.2
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    • pp.169-178
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    • 2009
  • In this study, we suggest Korean nonlinear fitting formula (KNFF) to maximize speech intelligibility for digital hearing aids based on NAL-NL1 (NAL-nonlinear, version 1). KNFF was derived from the same procedure which is used for deriving NAL-NL1. KNFF consider the long-term average speech spectrum of Korean instead of English because the frequency characteristic of Korean is different from that of English. New insertion gains of KNFF were derived using the SII (speech intelligibility index) program provided by ANSI. In addition, the insertion gains were modified to maximize the intelligibility of high frequency words. To verify effect of the new fitting gain, we performed speech discrimination test (SDT) and preference test using the hearing loss simulator from NOISH. In the SDT, a word set as test material consists of 50 1-syllable word generally used in hearing clinic. As a result of the test, in case of moderate hearing loss with severe loss on high frequency, the SDT scores of KNFF was more improved about 3.2% than NAL-NLl and about 6% in case of the sever hearing loss. Finally we have obtained the result that it was the effective way to increase gain of mid-high frequency bands and to decrease gain of low frequency bands in order to maximize speech intelligibility of Korean.

Optimal Design of Notch Filter in Photovoltaic Inverter (태양광 인버터의 노치 필터 최적 설계)

  • Kim, Yong-Rae;Heo, Cheol-Young;Lee, Young-Kwoun;Choy, Ick;Choi, Ju-Yeop
    • Journal of the Korean Solar Energy Society
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    • v.39 no.2
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    • pp.81-92
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    • 2019
  • When Photovoltaic inverter is connected to grid and used as PVPCS (Photovoltaic Power Conditioning System), 120 Hz AC ripple occurs at the dc-link capacitor voltage. This AC ripple reduces the efficiency of PVPCS and shortens the lifetime of the capacitor. In this paper, we design a notch filter to remove AC ripple. As a result, the AC voltage ripple was removed from the dc link and the THD of the PVPCS output current with the notch filter was lowered. This notch filter is determined by the damping coefficient, the bandwidth coefficient, and the switching frequency. Among these, the switching frequency determines the switching loss and the size of the LC filter, and the PVPCS with the high switching frequency has a greater efficiency loss due to the switching loss than the efficiency improvement by the notch filter. Therefore, it is important to set the optimum switching frequency in the PVPCS with the notch filter applied. In this paper, THD and switching loss of PVPCS output current with notch filter are calculated through simulation, and cost function to calculate optimum switching frequency through data is proposed.

고속용 영구 자석모터의 손실 특성

  • Jang, S.M.;Yang, H.S.;Jeong, S.S.;Rhu, D.W.;Choi, S.K.;Ham, Sang-Yong
    • Proceedings of the KIEE Conference
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    • 1999.11b
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    • pp.64-66
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    • 1999
  • High-speed motors using permanent magnet have various merits; high efficiency, high power density, and small size. While they have merits, we have to solve some problems. First of all, we have to reduce loss, cause of heat, to realize high speed operation. The loss be composed of copper loss, iron loss, and parasitic rotor loss. Iron loss and parasitic rotor loss is proportional to frequency, square of frequency, respectively.

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Transmission Loss Characteristics of the Panel Type Silencer (패널형 소음기의 투과손실 특성 연구)

  • 서상현;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.178-183
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    • 2003
  • This paper deals with transmission loss characteristics of the panel type silencer to control low frequency noise. The panel type silencer is composed of many Helmholtz resonators by side branch. Each resonator has high transmission loss on the narrow band of its resonance frequency. Direct arrangement of the resonators increases mainly the magnitude of transmission loss. If we arrange the resonators in a row, the peak and band of transmission loss are increased. This makes the resonator array to have high transmission loss in the broader band. Using this idea, we design a silencer that has broader band characteristics and smaller volume.

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Power Loss Calculation of High Frequency Transformers

  • Choi Geun-Soo;Yoon Shin-Yong;Baek Soo-Hyun;Kim Yong
    • Journal of Electrical Engineering and Technology
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    • v.1 no.3
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    • pp.338-342
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    • 2006
  • This paper analyzed the power loss of transformers considering the magnetic component. For this, each winding strategy and the effect of air gap between the ferrite core have been an important variable for optimal parameter calculation. Inductors are very well known design rules to devise, but the performance of the flyback converter as a function of transformer winding strategy has not been fully developed. The transformer analysis tool used was PExpert. The influence of the insulator thickness, effect of the air gap, how the window height and variation of the capacitive value effects the coil and insulator materials are some of parameters that have been analyzed in this work. The parameter analysis is calculated to a high frequency of 48[kHz]. Therefore, the final goal of this paper was to calculate and adjust the parameters according to the method of winding array and air gap minimizing the power loss.

Development of New Low Frequency ECT Sensor to Detect Inner Defects(I) - Characteristic of Loss of Induced Electromotive Force - (내부결함 검출 가능한 저주파 ECT 센서개발(I) - 전자기 유도기전력 손실량의 특성-)

  • Park, Jeong-Ung;Jang, Mun-Seok;Gim, Guk-Ju;Kim, Beom-Ki
    • Journal of Welding and Joining
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    • v.33 no.4
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    • pp.57-62
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    • 2015
  • Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing(ECT) is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. The New ECT sensor which can detect inner defects was developed regardless the condition of surface. This sensor is verified to do experiment which measure the loss of induced electromotive force. The loss of induced electromotive force was measured in 5.4% and this low frequency ECT device can detect internal defects at depth 20 mm.

A Study on the Dielectric Properties of Epoxy Composites with Frequency Variation (주파수 변화에 따른 에폭시 복합체의 유전특성에 관한 연구)

  • 김상걸;이동규;안준호;이상극;오현석;박건호;박우현;이기식;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.813-816
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    • 2001
  • In this paper, the dielectric properties of epoxy composites used for transformers are studied. The dielectric permittivity and loss of specimen are measured at the frequency range of 30[Hz]∼1[MHz] about temperature 20[$^{\circ}C$],100[$^{\circ}C$] and 140[$^{\circ}C$] respectively from a series of experiments. When the filler is added, between epoxy and silica is formed interface. Therefore, observed higher values of dielectric permittivity and loss in filled epoxy are attributed to MWS polarization effect. Also, glass transition temperature was shifted to higher temperature and value of dielectric permittivity and loss were decreased due to 2nd curing. Deformation of interfacial state is improved and value of dielectric permittivity and loss were decreased at low frequency region by the surface treatment of fillers with silane coupling agents.

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Acoustic Characteristics of a .Silencer by Using Array Resonators (공명기 배열을 이용한 소음기의 음향학적 특성)

  • 김양한;서상현
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.10
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    • pp.975-982
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    • 2004
  • Helmholtz resonator is used to reduce noise of the narrow frequency band. It has high transmission loss at its resonance frequency. The silencer that combines many resonators could control broadband noise at low frequency. To convey this rather simple idea, serial and parallel arrangement of resonators have been tested to obtain high transmission loss characteristics in the band of which are selects. Theoretical and experimental results explain these characteristics in the absence of mean flow. The change of acoustic characteristics by the resonance frequencies and resonators arrangement are explained by using the equivalent Impedance analysis that is defined in this paper. It shows that the transmission loss has a maximum value when the separation distance between each resonator is λ/4 of its wavelength.

Frequency dependence of AC loss in YBCO Bulk superconductor (YBCO Bulk 초전도체 교류손실의 주파수 의존성)

  • Ye, Jung-Hee;Nah, Wan-Soo;Kim, Chan-Jong;Hong, Gye-Won
    • Proceedings of the KIEE Conference
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    • 1999.07a
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    • pp.259-261
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    • 1999
  • In this paper, we investigated the frequency dependences of AC loss and the magnetic properties of a superconductor using magnetization method. We used the YBCO bulk superconductor sample which has a square-shaped cross sectional area of $6mm{\times}6mm$. and 43mm-long in axial direction. The applied AC magnetic field was parallel to the direction of sample axis. It is observed that YBCO bulk has the diamagnetic properties. AC loss calculation of YBCO bulk superconductor was performed by evaluating the total area of magnetization traces. We performed two cases of experiments, one for $B_m<B_p$ and the other for $B_m<B_p$. The experiments showed that the AC loss dependences on frequency were different in each mode, as was indicated in other publications.

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