• Title/Summary/Keyword: Constant frequency

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Frequency modulation of a waveguide cavity cw IMPATT diode oscillator (도파관캐비티를 사용한 임팻다이오드 발진기의 주파수변조특성)

  • 윤현보
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.12 no.6
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    • pp.1-4
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    • 1975
  • This paper dells with the impedance variations of the IMPATT diode depending upon the small a.c. coomponent superimposed on the d.c. bias. The frequency deviation of the modulated wave is measured using a carrier null method on microwave spectrum analyser. Frequency modulation is achieved by the weack a.c. signal superimposed on the d.c. bias. The bandwidth rapidly increase with increasing modulation signal magnitude for constant modulation frquency and slightly decrease with decreasing modulation frequency for constant modulation signal magnitude.

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Sliding Mode Control of a New Wind-Based Isolated Three-Phase Induction Generator System with Constant Frequency and Adjustable Output Voltage

  • Moradian, Mohammadreza;Soltani, Jafar
    • Journal of Power Electronics
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    • v.16 no.2
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    • pp.675-684
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    • 2016
  • This paper presents a new stand-alone wind-based induction generator system with constant frequency and adjustable output voltage. The proposed generator consists of a six-phase cage-rotor induction machine with two separate three-phase balanced stator windings and a three-phase space vector pulse width modulation inverter that operates as a static synchronous compensator (STATCOM). The first stator winding is fed by the STATCOM and used to excite the machine while the second stator winding is connected to the generator external load. The main frequency of the STATCOM is determined to be constant and equal to the load-requested frequency. The generator output frequency is independent of the load power demand and its prime mover speed because the frequency of the induced emf in the second stator winding is the same as this constant frequency. A sliding mode control (SMC) is developed to regulate the generator output voltage. A second SMC is used to force the zero active power exchanged between the machine and the STATCOM. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed generator system.

Static Dielectric Constant and Relaxation Time for the Binary Mixture of Water, Ethanol, N. N-Dimethylformamide, Dimethylsulphoxide, and N, M-Dimethylacetamide with 20Hethoxyethanol

  • Ajay Chaudgari;N. M. More;S. C. Mehrotra
    • Bulletin of the Korean Chemical Society
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    • v.22 no.4
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    • pp.357-361
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    • 2001
  • Frequency spectra of the complex permittivity of 2-methoxyethanol (2-ME) with water, ethanol, dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF) and N,N-dimethylacatamide (DMA) have been determined over the frequency range of 10 MHz to 20 GHz at 25 $^{\circ}C$, using the Time domain reflectometry method, for 11 concentrations for each system. The static dielectric constant, dielectric constant at microwave frequency, relaxation time, excess dielectric parameters, and Kirkwood correlation factor have been determined. The relaxation in these systems within the frequency range can be described by a single relaxation time constant, using the Debye model. The parameters show a systematic change with the concentration.

Current Controlled PWM for Multilevel Voltage-Source Inverters with Variable and Constant Switching Frequency Regulation Techniques: A Review

  • Gawande, S.P.;Ramteke, M.R.
    • Journal of Power Electronics
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    • v.14 no.2
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    • pp.302-314
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    • 2014
  • Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

Implement of Constant-Frequency-Controled Zero-Voltage-Switching Converter-fed DC Motor Drive for Low Power Loss (직류 전동기의 저손실 구동을 위한 일정 주파수 제어형 영전압 스위칭 변환기의 구현)

  • Ko, Moon-Ju;Park, Jin-Hong;Han, Wan-Ok;Lee, Sung-Paik
    • Proceedings of the KIEE Conference
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    • 1998.07f
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    • pp.2148-2150
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    • 1998
  • This paper proposes a constant frequency controlled zero voltage switching method that can reduce switching losses caused by emf on inductance in DC motor. The zero voltage switching method is used more than a zero current switching method because of reducing switching losses by capacitance of depletion region of MOSFET. To simplify the controller circuit, we propose constant frequency controlled zero voltage switching method in the paper. The control method is more stable than a variable frequency control method because it can optimize bandwidth of a closed-loop and reactances. Therefore, we construct a constant frequency controlled zero voltage switching converter and improve zero switching losses in high switching frequency. In the process, we can control low-losses in full range on variable voltage and load. We simulate the proposed converter with P-SPICE and compare results obtained through the experiment.

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Design of LLCL Filter for Single Phase Inverters with Confined Band Variable Switching Frequency (CB-VSF) PWM

  • Attia, Hussain A.;Freddy, Tan Kheng Suan;Che, Hang Seng;El Khateb, Ahmad H.
    • Journal of Power Electronics
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    • v.19 no.1
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    • pp.44-57
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    • 2019
  • Recently, the use of LLCL filters for grid inverters has been suggested to give better harmonic attenuation than the commonly used L and LCL filters, particularly around the switching frequency. Nevertheless, this filter is mainly designed for constant switching frequency pulse width modulation (CSF PWM) methods. In variable switching frequency PWM (VSF PWM), the harmonic components are distributed across a wide frequency band which complicates the use of a high order filter, including LCL and LLCL filters. Recently, a confined band variable switching frequency (CB-VSF) PWM method has been proposed and demonstrated to be superior to the conventional constant switching frequency (CSF) PWM in terms of switching losses. However, the applicability of LLCL filters for this type of CB-VSF PWM has not been discussed. In this paper, the authors study the suitability of an LLCL filter for CB-VSF PWM and propose design guidelines for the filter parameters. Using simulation and experimental results, it is demonstrated that the effectiveness of an LLCL filter with CB-VSF PWM depends on the parameters of the filters as well as the designed variable frequency band of the PWM. Simulation results confirm the performance of the suggested LLCL design, which is further validated using a lab scale prototype.

Dielectric Properties of Complex Cconcentration in IMI-0 Thin Films (IMI-O 초박막의 착체농도에 대한 유전 특성)

  • 정상범;유승엽;박재철;권영수
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.05a
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    • pp.345-348
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    • 1999
  • The monolayer behaviors at the air-water interface and the dielectric properties of MI-0 LB films for complex concentration were investigated by the surface pressure-area ($\pi$-A) isotherms and dielectric constant. The molecular area was expanded with increase of metal ions concentration. It is considered that the expansion of molecular area is due to electrostatic repulsion between the polymer chains andhydrophobic increase of ionic strength. In the frequency-dependent complex dielectric constant at room temperature, the real part of dielectric constant($\varepsilon'$) is about 6.0~10.0 in the low-frequency range and is decreasing slowly upto $1O^4$Hz. It decreased abruptly near $1O^5Hz$. It seems to be dielectric dispersion in this frequency range. Also, the imaginary part of dielectric constant ($\varepsilon"$) shows a peak in $1O^5$~$1O^6Hz$. It seems to be dielectric absorption in this frequency range.ange.

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Improvement of Dynamic Response for IPMSM based on DTC-CFTC Using Sliding Mode Control (일정 스위칭 주파수를 가지는 DTC 기반 IPMSM의 슬라이딩 모드 제어를 이용한 속응성 향상)

  • Han, Byeol;Bak, Yeongsu;Lee, Kyo-Beum
    • Journal of IKEEE
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    • v.23 no.2
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    • pp.628-635
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    • 2019
  • This paper proposes sliding mode control (SMC) method for improvement of dynamic response for IPMSM based on DTC with constant switching frequency. DTC with constant switching frequency method consists of PI torque controller and triangular comparator for constant torque error status. It has the poor dynamic response compared to conventional DTC. This paper proposes improvement method of dynamic response of DTC with constant switching frequency by using SMC. Simulation results confirm the effectiveness of the proposed method.

Effects of Calcining Temperature on Planar Coupling Factor and Resonance Charcteristics of BaTiO3 (하소온도가 BaTiO3 세라믹의 Kp와 공진특성에 미치는 영향)

  • 정수태;조상희
    • Journal of the Korean Ceramic Society
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    • v.23 no.6
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    • pp.66-70
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    • 1986
  • The calcining temperature ranging from 900$^{\circ}C$ to 1300$^{\circ}C$ affected on the planar coupling factor and resonance characteristics of BaTiO3 ceramics doped with 0.2 wt% MnO2 have been investigated. Dielectric constant planar coupling factor and anti-resonance frequency of the sample increased with the calcining temperature up to 1,200$^{\circ}C$ and decreased above that temperature but the resonance frequency decreased slightly with the increasing calcining temperature. The planar coupling factor and anti-resonance frequency increased with the sintered density and dielectric constant while the resonance frequency was almost constant. The resonance and anti-resonance frequency increased with the sample temperature.

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A New Control Scheme for a Class-D Inverter with Induction Heating Jar Application by Constant Switching Frequency

  • Choi Won-Suk;Park Nam-Ju;Lee Dong-Yun;Hyun Dong-Seok
    • Journal of Power Electronics
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    • v.5 no.4
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    • pp.272-281
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    • 2005
  • In this paper, a simple power control scheme for a constant frequency Class-D inverter with a variable duty cycle is proposed. It is more suitable and acceptable for high- frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease of control output power. Also it can achieve a stable and efficient Zero-Voltage-Switching (ZVS) in a whole load range. The control principles of the proposed method are described in detail and its validity is verified through simulated and experimental results on 42.8kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.