• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2300-2307
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• 2008

This study receives the noise transmitted in a constant audio frequency range through a microphone array in which the noise(like grease in a pan) occurs on the power supply line due to the troublesome partial discharge(arc). Then by going through a series of signal processing of removing noise, this study measures the distance and direction up to the noise caused by the troublesome partial discharge(arc) and monitors the result by displaying in the analog and digital method. After these, it determines the state of each size and judges the distance and direction of problematic part. When the signal sound transmitted by the signal source of bad insulator is received on each microphone, the signal comes only in the frequency range of 20 kHz by passing through the circuit of amplification and 6th low pass filter. Then, this signal is entered in a digital value of digital signal processing(TMS320F2812) through the 16-bit A/D conversion. By doing so, the sound distance, direction and coordinate of bad insulator can be detected by realizing the correlation method of detecting the arriving time difference occurring on each microphone and the algorithm of detecting maximum time difference.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1183-1184
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• 2011

In case of the power conversion converter for driving the Lighting control system, the input voltage widens from $90V_{rms}$ to $264V_{rms}$. Among various methods, LLC half-bridge converter has wide input regulation range and limited switching frequency control range and ZVS is possible for even non-loaded case. Also, the converter can be applied for Universal Lighting control system. In this paper, the transformer design is studied. The efficiency measured is up to 90%.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.26-29
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• 2000

The conventional types of X-ray generators were bulky in physical size and heavy in weight and the control accuracies of the output voltages were not always satisfacotry. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing power semiconducot devices. To decreasing the volume and the weight of high voltage transformer and to stabilize ripple. In this paper the newly developed x-ray generator in a low cost using duty modulation PWM inverter. This system verify improved performance by stabilize ripple of X-ray tube voltage and compared the reproducibility linearity and dose in single phase three phase and PSU.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.64-65
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• 2011

The ac power conversion inverter provides the ac power to ECR device for wireless power transfer. In this paper, the operating efficiency of the class-${\Phi}_2$ resonant inverter has been studied through by experiment for optimal design. Its switching frequency is 1MH and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output voltage is 230Vp-p. The efficiency is measured up to 84%.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.980-982
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• 2001

SRM has different characteristics according to their control methods. Therefore, A new magnetizing method with a low-frequency increasing the energy conversion ratio that is related to the efficiency of motor is proposed. As results, it improved the efficiency about 2(%) and decreased the noise level up to 5[dB]. And a torque ripple is also sufficiently reduced compared with that of the conventional switching angle magnetizing approach.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.51-58
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• 2020

In this study, a novel method for sweeping automatic linearization of wavelength swept laser is proposed. Through the test performed on the implemented laser, the linear sweeping is held up well with a 97% decrease in nonlinearity, and 60 nm sweeping range, 1 kHz sweeping frequency, and 8.8 mW average optical power were obtained. The proposed method uses fiber Bragg grating array, optical-electronic conversion circuit, FPGA embedded module, and a LabVIEW program to generate new compensated wave patterns which were applied to the fiber Fabry-Perot tunable filter. Linear sweeping can reduce the cumbersome and time-consuming recalibration process required for nonlinear sweeping. Additionally, the proposed method provides more accurate measurement results for the structure safety monitoring system.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.358-365
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• 2005

In induction machine drive without a speed sensor, the estimation of the motor flux and speed often becomes deteriorated at low speeds with low back EMF. Our analysis shows that, in addition to the state resistance variation, the estimated value of field orientation angle is often corrupted by accumulative errors from the integration of voltage variables at motor terminals that have low signal/noise ratio at low frequencies. A repetitive loop path of integration in the feedback can amplify this type of error, thus speeding up the degradation process. The control system runs into information starvation due to the loss of correct field orientation. The machine's spiral vectors are controlled only in a reduced dimension in this situation. A novel control scheme is developed to improve the control performance of motor's current, torque and speed at low frequencies. The scheme gains a full-dimensional vector control and is less sensitive to the combined effect of the error sources at the low frequencies. Experimental tests demonstrate promising performances are achievable even below 0.5 Hz.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.412-419
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• 2020

In this study, a PID control method for sweeping automatic linearization of a wavelength swept laser is proposed. First, the closedloop transfer function embodying the PID control is derived. Through the simulation of the function, K_p = 0.022, K_i = 0.008, K_d = 0.002 were obtained as the best PID coefficients for fast linear sweeping. The performance test using the PID coefficients showed that linear sweeping was held up well with a 98.7% decrement in nonlinearity after the 10th feedback, and 45 nm sweeping range, 1 kHz sweeping frequency, and 8.8 mW average optical power were obtained. The equipment consists of a fiber Bragg grating array, an optical-electronic conversion circuit, and a LabVIEW FPGA program. Every 5s, automatic feedback and PID control generate a new compensated waveform and produce a better linear sweeping than before. Compared with nonlinear sweeping, linear sweeping can reduce the cumbersome and time-consuming recalibration processes and produce more accurate measurement results.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.27-28
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• 2015

In this paper a high efficiency wireless on-board charger for Electric Vehicle (EV) is proposed and the theoretical analysis based on the two-port network model to come up with suitable design for the battery charge application is presented. The proposed Wireless Power Transfer (WPT) method has adopted four-coil system with air core and its superior performance is proved by comparing it to the conventional two-coil system by the mathematical analysis. In addition, since the proposed WPT converter is able to operate at an almost constant frequency regardless of the load, CC/CV charge of the battery can be simply implemented. A 6.6kW prototype is implemented with 20cm air gap to prove the validity of the proposed method. The experimental results show that the dc to dc conversion efficiency of the proposed system achieves 97.08% at 3.7 kW.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2441-2446
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• 2018

This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using $0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current.