• Title/Summary/Keyword: Harmonics spectra

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Pseudo-Randomized Frequency Carrier Modulation Scheme with Improved Harmonics Spectra Spreading Effects (고조파 스펙트럼 확산효과를 개선한 준 랜덤 주파수 캐리어 변조기법)

  • Kim, Jong-Nam;Jung, Young-Gook;Lim, Young-Cheol
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.22 no.12
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    • pp.64-70
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    • 2008
  • In case that conventional PRC(Pseudo-Randomized Frequency Carrier) modulation scheme is applied to a three-phase HBML(H-Bridge Multi-Level Inverter), the dominant harmonics spectra appear at twice switching frequency. In this paper, the dominant harmonics spectra spreading effect of the conventional PRC scheme was improved by using three stage MUXs(Multiplexers) and two triangular carriers with fixed frequency which has mutual relation of the twice frequency. To confirm the validity of the improved PRC scheme, the experiment were performed on a 1.5[kw] three-phase HBML based induction motor drives. And, the harmonics spectra of the conventional and improved PRC schemes are compared and discussed.

Analysis on Waveform of Leakage Current of Contaminated EPDM Insulators by Salt Fog (Salt fog에 의한 오손된 EPDM애자의 누설전류 파형 분석)

  • Park, Jae-Jun;Song, Young-Chul;Kim, Jeong-Boo;Lee, You-Min;Lee, Hyun-Dong;Jung, Young-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.36-41
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    • 2003
  • This paper presents the results of power spectra using the fundamental and low frequency harmonic components of leakage current waveform to study aging on contaminated EPDM insulator(was serviced during 1997-2001, region Pohang, korea) under salt fog conditions. Experiments have been conducted in the chamber salt fog and at the 16KVrms. The salt contents adjusted as 0g,25g,50g and 75g per liter of deionized water. The onset of dry-band arcing on polymer insulators could be determined by signal processing the low frequency harmonics components. A correlation has been found between the fundamental and low harmonic components of power spectra on leakage current. Where aging could be associated with an increase in the level of both the fundamental and low frequency harmonics components of leakage current. Surface aging for contaminated EPDM insulators occurred when the fundamental component of leakage current was greater then some level On the other hand, when the polymer insulator approached failure, the fundamental component of leakage current reached relatively high values and low frequency harmonics components of the leakage current trended to decrease. The results suggest that both the fundamental and low frequency harmonics of leakage current can be used as a tool to determine both the beginning of aging and before flashover, end of life EPBM insulator in salt fog.

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Tidal and Sub-tidal Current Characteristics in the Kangjin Bay, South Sea, Korea

  • Ro, Young-Jae
    • Ocean Science Journal
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    • v.42 no.1
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    • pp.19-30
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    • 2007
  • This study analyzed the current meter records along with wind records for over 500 days obtained in the Kangjin Bay, South Sea, Korea spanning from March, 2003 to Nov. 2005. Various analyses include descriptive statistics, harmonic analysis of tidal constituents, spectra and coherence, the principal axis, progressive vector diagrams. These analyses can illustrate the response of residual current to the local wind resulting in the net drift with rotational motion. Current speed ranges from -28 to 33 (cm/sec), with standard deviations from 6.5 to 12.9 (cm/sec). The harmonic analyses of the tidal current show the average form number, 0.12 with semi-diurnal type and the rectilinear orientation of the major axis toward northeast. The magnitudes of the semi-major range from 12.7 to 17.7 (cm/sec) for M2 harmonics, while for S2 harmonics, they range from 6.3 to 10.4 (cm/sec), respectively. In the spectral and coherency analysis of residual current and wind, a periodicity of 13.6 (day) is found to be most important in both records and plays an important role in the net drift of residual current. The progressive vector diagrams of residual current and wind show two types of behaviors such as unidirectional drift and rotational motion. It was also found that 3 % rule holds approximately to drive 1 (cm/sec) drift current by 30 (cm/sec) wind speed based on the correlation of the semi-major axis of wind and residual current.

A Study on the Characteristics of Sound Source of Hydrodynamic proceeding Bearings (유체 윤활 저널베어링의 음원 특성에 관한 연구)

  • Rho, Byoung-Hoo;Kim, Kyung-Woong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.05a
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    • pp.156-161
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    • 2002
  • Results of theoretical investigations on acoustical properties of hydrodynamic proceeding bearings are presented. Nonlinear analysis of rotor bearing system including rotor imbalance is performed in order to obtain acoustical properties of hydrodynamic proceeding bearings. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties of hydrodynamic proceeding bearings are identified through frequency analysis of pressure fluctuation calculated from the nonlinear transient analysis. The results show that the acoustical frequency spectra of hydrodynamic proceeding bearings are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that the super-harmonics are predominant at neighborhood of the fluid film reformation and rupture regions.

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A Pseudo-Random Carrier PWM Technique by Fixed Frequency Carrier Composition (고정 주파수의 캐리어 합성에 의한 준 랜덤 주파수 캐리어 PWM기법)

  • Kim, Jong-Nam;Jung, Young-Gook;Lim, Young-Cheol;Park, Sung-.Jun;Kim, Kwang-Heon
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.11
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    • pp.547-552
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    • 2005
  • This paper describes a pseudo-random carrier PW technique for the power converters. The proposed method generates a new pseudo-random carrier by randomly composing a carrier with fixed frequency and a carrier with opposition phase. To confirm the validity of the proposed method, a single-phase multi-level inverter was implemented and tested. The experimental results show that the output voltage and current harmonics spectra of an inverter have broadening effect of harmonics, as only simple composition of fixed frequency carries.

A Study on the Characteristics of Sound Source of Hydrodynamic Journal Bearings (유체 윤활 저널 베어링의 음원 특성에 관한 연구)

  • Rho, Byoung-Hoo;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • v.18 no.5
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    • pp.333-338
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    • 2002
  • Results of theoretical investigations on acoustical properties of hydrodynamic journal bearings are presented. Nonlinear analysis including rotor imbalance is performed for a rotor-bearing system in order to obtain acoustical properties of hydrodynamic journal bearings. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties of hydrodynamic journal bearings are identified through frequency analysis of oil pressure fluctuation calculated from the nonlinear transient analysis. The results show that the acoustical frequency spectra of the fluid film are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that super-harmonics are predominant at the neighborhood of the fluid film reformation and rupture regions.

The Analysis of Acoustic Emission Spectra in a 36 kHz Sonoreactor (36kHz 초음파 반응기에서의 원주파수 및 파생주파수의 음압 분포 분석)

  • Son, Younggyu
    • Journal of Soil and Groundwater Environment
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    • v.21 no.6
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    • pp.128-134
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    • 2016
  • Acoustic emission spectra was analyzed to investigate the distribution of sound pressure in a 36 kHz sonoreactor. The sound pressure of fundamental frequency (f: 36 kHz), harmonics (2f: 72 kHz, 3f: 108 kHz, 4f: 144 kHz, 5f: 180 kHz, 6f: 216 kHz), and subharmonics (1.5f: 54 kHz, 2.5f: 90 kHz, 3.5f: 126 kHz, 4.5f: 162 kHz, 5.5f: 198 kHz, 6.5f; 234 kHz) was measured at every 5 cm from the ultrasonic transducer using a hydrophone and a spectrum analyzer. It was revealed that the input power of ultrasound, the application of mechanical mixing, and the concentration of SDS affected the sound pressure distributions of the fundamental frequency and total detected frequencies frequencies significantly. Moreover a linear relationship was found between the average total sound pressure and the degree of sonochemical oxidation while there was no significant linear relationship between the average sound pressure of fundamental frequency and the degree of sonochemical oxidation.

Time-frequency Analysis of Train Vibration Using Order Analysis and Correlation (오더분석 및 상관관계를 활용한 철도차량 진동 데이터의 시간-주파수 분석)

  • Choi, Sung-Hoon;Igusa, Takeru;Park, Choon-Soo
    • Journal of the Korean Society for Railway
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    • v.12 no.6
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    • pp.989-995
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    • 2009
  • Short-time Fourier transforms (STFT) are useful for analyzing signals with harmonics that vary with time. If the variation of the harmonics with time is smooth, such as in kinematic vibrations in vehicles, then it is possible to improve the STFT using order spectra and correlation analysis. In this paper, it is shown how correlation analysis can be performed when the speed signal is noisy or unknown and then it is shown how order spectra become simple to compute after this analysis. The results are illustrated by an analysis of axle and car body vibrations in the prototype high-speed train, HSR-350x.

FREQUENCY SELECTIVE RECURSIVE LP OF HARMONIC SPECTRA

  • SeungHyonNam
    • Journal of the Korean Geophysical Society
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    • v.4 no.4
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    • pp.231-238
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    • 2001
  • In this paper, an efficient LP method ofr discrete harmonic spectra is proposed and discussed. A new efficient LP method is a combination of recursive and frequency selective LP. While the recursive LP provides better spectral matching in spectral hills, frequency selective LP eliminates numerical instability and improves spectral matching when the harmonics are confined in the low frequncy region. The proposed LP method is applied to the HILN coder. Simulation results using a verification model(VM) software for real audio signals show a definite trend of significant improvement.

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Frequency Selective Recursive LP of Discrete Harmonic Spectra for Audio Cording

  • Nam, Seung-Hyon
    • The Journal of Engineering Research
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    • v.5 no.1
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    • pp.37-44
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    • 2004
  • n this paper, an efficient LP method for discrete harmonic spectra is proposed and discussed. A new efficient LP method is a combination of recursive and frequency selective LP. While the recursive LP provides better spectral matching in spectral hill, frequency selective LP eliminates numerical instability and improves spectral matching when the harmonics are confined in the low frequency region. The proposed LP method is applied to the HILN coder. Simulation results using a verification model(VM) software for real audio signals show a definite trend of significant improvement.

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