• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.349-356
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• 2021

Permanent magnet synchronous motors are mainly used in the traction of electric vehicle and home application products including air-conditioners and refrigerators. For sensorless control without rotor position sensors, I-F control is applied for initial starting at low speeds, and mode is changed to sensorless control when the rotor speed is sufficiently accelerated for estimating rotor position. When the mode is changed to the sensorless control from the open-loop starting, the initial integral value of the speed controller should be considered by load condition; otherwise, the transition to sensorless control may fail. The sensorless transfer algorithm of PM synchronous motor based on load condition for smooth transition is proposed. The performance of the proposed sensorless transfer algorithm was verified by experiments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.3
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• pp.155-163
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• 2023

Real-time monitoring technology is critical for ensuring the safety and reliability of nuclear power plant structures. However, the current seismic monitoring system has limited system identification capabilities such as modal parameter estimation. To obtain global behavior data and dynamic characteristics, multiple sensors must be optimally placed. Although several studies on optimal sensor placement have been conducted, they have primarily focused on civil and mechanical structures. Nuclear power plant structures require robust signals, even at low signal-to-noise ratios, and the robustness of each mode must be assessed separately. This is because the mode contributions of nuclear power plant containment buildings are concentrated in low-order modes. Therefore, this study proposes an optimal sensor placement methodology that can evaluate robustness against noise and the effects of each mode. Indicators, such as auto modal assurance criterion (MAC), cross MAC, and mode shape distribution by node were analyzed, and the suitability of the methodology was verified through numerical analysis.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.376-382
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• 2004

The interaction between a vibrating structure and a surrounding acoustic medium determines the acoustic power propagating into the far-field. A straightforward method to reduce the radiated power is to reduce the vibration of the structure. However it is more efficient to control the modes of the structure separately since each vibration mode of the structure has different radiation efficiency. An efficient method to reduce the sound radiation in the low frequency region is proposed by reducing the radiation efficiency of the structure. Numerical simulations are carried out for a simply-supported beam in which the feed-forward control is applied to reduce the volume velocity of each structural mode. This method is found to be very efficient in reducing low frequency sound radiation.

• Journal of Drive and Control
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• v.19 no.3
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• pp.32-38
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• 2022

The in-wheel drive gearbox for military special vehicles converts the high-speed & low-torque output generated by the electric servomotor, into low-speed & high-torque mechanical power. As the vehicle is remotely maneuvered in mountainous terrain, wet fields, rough terrain, etc., the gearbox must generate a maximum input speed exceeding 5,000 rpm, a maximum torque of 245 Nm, and MTBF of 9,600 km. The purpose of this study was to analyze the failure mode of the gearbox, to ensure the durability of the in-wheel drive gearbox. Also, the field load test data of the vehicle was analyzed, the acceleration durability test standards were established, the acceleration durability test was conducted, and the durability test results were analyzed as well.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.469-472
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• 2004

In this paper a current mode sense amplifier suitable for 30nm SONOS flash memories read operation is presented. The proposed sense amplifier employs cross coupled latch type circuit and current mirror to amplify signal from selected memory cell. This sense amplifier provides fast response in low voltage and low current dissipation. Simulation results show the sensing delay time and current dissipation for power supply voltages Vdd to expose limitations of the sense amplifier in various operating conditions.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2016-2019
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• 1997

To solve the low efficiency problem of low-voltage power supplies, it has been studied to replace the schottky barrier diode with the MOSFET synchronous rectifier. In this paper, Phase Shift-Controlled Clamp Mode Zero Voltage Switching-Multi Resonant Converter with Synchronous Rectifier (PSC CM ZVS-MRC with SR) is presented to achieve high efficiency in low-voltage power supplies. The characteristics analysis of synchronous rectifier is established by using the MOSFET equivalent circuit and efficiency comparison is established between the Synchronous Rectifier and the schottky barrier diode. To verify the validity of the analysis, 33W(3.3V, 10A) PSC CM ZVS-MRC with self-driven synchronous rectifier at switching frequency of 1MHz is designed and tested. And it is confirmed that the experimental results are well consistent with the theoretical results. The maximum efficiency of the converter is 83.4% at full load, which is 3.3% higher than conventional schottky diode rectification.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.6
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• pp.51-57
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• 1997

Low-voltage, low-power gm-C filter utilizing newly dveloped operational transconductance amplifier (OTA) is described in this paper. The OTA has only two MOS transistors in saturation region between $V_{DD}$ and GND, and thus low voltage operation is possible. To improve the linearity, the OTA is made differential. Common mode feedback, essential in differential circuit, requires no additional implemented in $0.8\mu\textrm{m}$ CMOS process, and the center frequency can be controlled from 15MHz with 3.0V single power supply.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.416-421
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• 2011

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate $Pb(Zr,Ti)O_3$ (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm${\times}$3 mm${\times}$0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.

• Journal of Power Electronics
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• v.18 no.4
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• pp.997-1006
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• 2018

This paper proposes a transformerless photovoltaic (PV) power converter system based on the DC/AC boost inverter, which can solve the leakage current and second-order ripple power issues in single-phase grid-connected PV inverters. In the proposed topology, the leakage current can be decreased remarkably since most of the common-mode currents flow through the output capacitor, by-passing parasitic capacitors, and grounding resistors. In addition, the inherent ripple power component in the single-phase grid inverter can be suppressed without adding any extra components. Therefore, bulky electrolytic capacitors can be replaced by small film capacitors. The effectiveness of the proposed topology has been verified by simulation and experimental results for a 1-kW PV PCS.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.519-526
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• 2003

A singl-phase power factor corrected converter for switched reluctance motor hive is presented to achieve a sinusoidal and new unity power factor input currents. Because it combines a power factor corrected converter and a conventional asymmetric SRM driver into one power stage, the configuration has a simple structure resulted in low cost. A prototype to drive 6/6 poles SRM employing a parking magnet Is designed to evaluate the proposed topology. The characteristics and operational mode will be discussed in depth, and the validity of proposed driver will be verified through the experimental results.