• Title/Summary/Keyword: Short pulses injection

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Initial Rotor Position Estimation of an IPMSM Based on Least Squares Approximation with a Polarity Identification (극성 판별이 가능한 최소 제곱법 기반의 IPMSM 회전자 초기 위치 추정)

  • Kim, Keon Young;Bak, Yeongsu;Lee, Kyo-Beum
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.1
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    • pp.72-75
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    • 2018
  • An initial rotor position estimation method is proposed in this study for an interior permanent-magnet synchronous motor without a resolver or an absolute encoder. This method uses least squares approximation to estimate the initial rotor position. The magnetic polarity is identified by injection of short pulses. The proposed estimation process is robust because it does not require complex signal processing that depends on the performance of a digital filter. In addition, it can be applied to various servo systems because it does not require additional hardware. Experimental results validate the effectiveness of the proposed method using a standard industrial servomotor with interior-permanent magnets.

Optical Millimeter-wave Signal Generation using Injection Locking Scheme (광주입 방법을 이용한 밀리미터파 신호 생성)

  • Kim, Jung-Tae
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.7 no.5
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    • pp.1076-1081
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    • 2003
  • A new technique for generating millimeter-wave signals from a semiconductor laser is presented. The method multiples the signal frequency by using optical injection of short optical pulses at a sub-harmonic of the cavity round-trip frequency to drive the laser oscillating at its resonant frequency. A 32GHz signal is generated using a multisection semiconductor laser operated under continuous wave conditions, by injection optical pulses at a repetition rate equal to the fourth subhamonic(8GHz). The generated millimeter-wave signal exhibits a large submamonic suppression ratio(>17 dB), large frequency detuning range (>300 MHz) low levels of phase-noise(-77.5 dBc/Hz), and large locking (>400 MHz)

Fabrication and Characteristics of DFB Laser with Absorption Grating (흡수격자를 갖는 DFB 레이저의 제작 및 특성)

  • 이형종
    • Proceedings of the Optical Society of Korea Conference
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    • 1990.02a
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    • pp.73-78
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    • 1990
  • 1.3${\mu}{\textrm}{m}$ DFB with absorption grating of 1.55${\mu}{\textrm}{m}$ InGaAsP layer was fabricated. This new type of DFB laser shows self-plusation for DC operation. At low level of injection the relation between the pulsation frequency and the injection current shows similar behavior with the relaxation oscillation of ordinary laser and at high level of injection the pulsation frequency decreases compared to the relaxation oscillation. Period doubling, period 3 and 4 were observed for AC modulation. In case of period doubling the waveform shows only one pulse within a period without any accompanying subsidiary pulses and the oscillation frequency was quite stable. The pulse widths as short as 58.5 ps was achieved with AC modulation. We propose the time division multiplexing application of this kind of DFB laser.

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Simulations for the cesium dynamics of the RF-driven prototype ion source for CRAFT N-NBI

  • Yalong Yang;Yong Wu;Lizhen Liang;Jianglong Wei;Rui Zhang;Yahong Xie;Wei Liu;Chundong Hu
    • Nuclear Engineering and Technology
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    • v.56 no.4
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    • pp.1145-1152
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    • 2024
  • To realize an initial objective of the negative ion-based neutral beam injection (N-NBI) at the Comprehensive Research Facility for Fusion Technology (CRAFT) test facility, which targets an H0 beam power of 2 MW at an energy of 200-400 keV and a pulse duration of 100 s, it is crucial to study the cesium dynamics of the negative ion source. Here a numerical simulation program CSFC3D is developed and applied to simulate the distribution and time dynamics of cesium during short pulses. The calculations show that most of the cesium on the plasma grid (PG) area originates from the release of cesium that is accumulated within the ion source in the plasma phase. Increasing the wall temperature reduces the loss of cesium on the wall of the ion source. Furthermore, the thickness of the cesium monolayer is directly influenced by the PG temperature. Both simulated and experimental results demonstrate that maintaining the PG temperature between 180 ℃ and 200 ℃ is essential for enhancing the performance of the ion source and optimizing the cesium behavior.

Frequency-dependent grounding impedance of the counterpoise based on the dispersed currents

  • Choi, Jong-Hyuk;Lee, Bok-Hee;Paek, Seung-Kwon
    • Journal of Electrical Engineering and Technology
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    • v.7 no.4
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    • pp.589-595
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    • 2012
  • When surges and electromagnetic pulses from lightning or power conversion devices are considered, it is desirable to evaluate grounding system performance as grounding impedance. In the case of large-sized grounding electrodes or long counterpoises, the grounding impedance is increased with increasing the frequency of injected current. The grounding impedance is increased by the inductance of grounding electrodes. This paper presents the measured results of frequency-dependent grounding impedance and impedance phase as a function of the length of counterpoises. In order to analyze the frequency-dependent grounding impedance of the counterpoises, the frequency-dependent current dissipation rates were measured and simulated by the distributed parameter circuit model reflecting the frequency-dependent relative resistivity and permittivity of soil. As a result, the ground current dissipation rate is proportional to the soil resistivity near the counterpoises in a low frequency. On the other hand, the ground current dissipation near the injection point is increased as the frequency of injected current increases. Since the high frequency ground current cannot reach the far end of long counterpoise, the grounding impedance of long counterpoise approaches that of the short one in the high frequency. The results obtained from this work could be applied in design of grounding systems.

Rotor Time Costant Compensation for Vector-Controlled IM with DC Current Injection Method (직류전류 주입법에 의한 벡터제어 유도전동기의 회전자 시정수 보상)

  • Lee, K.J.;Nam, H.T.;Choi, J.W.;Kim, H.G.;Lee, D.K.;Chun, T.W.;Nho, E.C.
    • Proceedings of the KIEE Conference
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    • 2001.04a
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    • pp.285-287
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    • 2001
  • To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

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Rotor Time Constant Compensation for Vector-Controlled Induction Motor with DC Current Injection Method (직류전류 주입법에 의한 벡터제어 유도전동기의 회전자 시정수 보상)

  • Lee, Gyeong-Ju;Lee, Deuk-Gi;Jeong, Jong-Jin;Choe, Jong-U;Kim, Heung-Geun;No, Ui-Cheol;Jeon, Tae-Won
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.2
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    • pp.69-76
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    • 2002
  • To obtain a high performance in a vector controlled induction motor, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantage with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations and experimentals.

MREIT Conductivity Imaging of Pneumonic Canine Lungs: Preliminary Post-mortem Study

  • Kim, Hyung-Joong;Kim, Young-Tae;Jeong, Woo-Chul;Minhas, Atul S.;Lee, Tae-Hwi;Lim, Chae-Young;Park, Hee-Myung;Kwon, O-Jung;Woo, Eung-Je
    • Journal of Biomedical Engineering Research
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    • v.31 no.2
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    • pp.94-98
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    • 2010
  • In magnetic resonance electrical impedance tomography (MREIT), a current-injection MR imaging method is adopted to produce a cross-sectional image of an electrical conductivity distribution in addition to MR images. The purpose of this study was to test the feasibility of MREIT for differentiating the canine lung parenchyma without and with pneumonia. Three normal healthy beagles and two mixed breed dogs with pneumonia were used. After attaching electrodes around the chest, we placed the dog inside our MR scanner. We injected as much as 30 mA current in a form of short pulses into the chest region. Reconstructed conductivity images of normal canine lungs exhibit a peculiar pattern of a relatively coarse salt and pepper noise. On the contrary, conductivity images of pneumonic canine lungs show significantly enhanced contrast of the lesions while the corresponding MR images show a little bit of contrast in the middle and caudal lung parenchyma due to the accumulation of pleural fluid. This preliminary study indicates that MREIT imaging of the chest may deliver unique new diagnostic information.