• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.466-469
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• 2001

In this paper, closed loop V/f control of induction motor has been implemented by the estimated speed. Closed loop V/f control improve the performance of induction motor drive system at low speed compared to open loop V/f control. However, closed loop V/f control need speed sensor. By using the estimated speed, closed loop V/f control is possible without speed sensor. Rotor speed is calculated from the difference between synchronous frequency and slip angular frequency. 3-phase voltage reference is obtained from synchronous frequency. And the PWM technique using space vector PWM is applied in this scheme. In the space vector PWM, effective time of 3-phase voltage reference is used to simplify the calculation of effective voltage time. This scheme is simple to implement and one chip microprocessor was used in experimental system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1621-1625
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• 2010

Recently, due to increase in the usage of toxic gas and inflammability gas, the ability to monitor and precisely measurement of these gases is crucial in preventing the occurrence of various accidents. CuO doped and undoped $WO_3$ thick films gas sensors were prepared using screen-printing method on alumina substrates. A structural properties of $WO_3$:CuO thick films had monoclinic phase and triclinic phase of $WO_3$ together. Sensitivity of $WO_3$:CuO sensor at 2000 ppm of $CO_2$ gas and 50 ppm of $H_2S$ gas was investigated. 4 wt% Cu doped $WO_3$ thick films had the highest sensitivity of $CO_2$ gas and $H_2S$ gas.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.649-654
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• 2003

The simplest method for measuring output currents of the three phase inverters is to measure them with three current sensors such as hall sensors. This method requires at least two current sensors, and these types of sensors are somewhat expensive. More economical method is measuring DC link current with a simple shunt resistor, then, reconstructing output current using the DC link current value and the switching status. However, in low speed region, the measurement becomes difficult and even impossible due to the requirement of minimum switching duration for A/D conversion. These problems can be overcome by limitation of switching duration. Limitation of switching, however, causes voltage and current distortion. Owing to compensation, distortion can be effectively suppressed. However these increase acoustic noise due to increment of current ripple. In this paper, a current measurement method is proposed, which can reduce minimum switching duration resulting in reduction of acoustic noise. The validity of proposed method is confirmed through experiment.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.211-212
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• 2012

This paper proposes a single current sensor control technique for controlling motors that use only a single DC-Link current sensing resistor to obtain the information of three line currents. However, the measurement is distorted due to the too narrow current pulse width in the shunt resistor. To solve this problem, the existing phase current reconstruction methods are voltage split methods. They have a disadvantage which makes noise. A new dedicated observer is applied to decrease noise problem. Experimental results showed the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.4
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• pp.188-200
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• 2001

This paper presents a technique for reconstructing converter line currents using the information from a single current sensor in the DC-link for voltage-source PWM converters. When three-Phase input currents cannot be reconstructed, three methods to acquire the input current are compared. Two of them are methods of modifying the switching state (I, II), another is a method of using the predictive state observer. Also, compensation of sampling delay, and a simultaneous sample value of input currents in the center of a switching period are included. Suitable criteria for the comparison are identified, and the differences in the performance of these methods are investigated through experimental results for a typical V-S PWM converter rated at 10kVA.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.436-438
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• 2005

본 논문에서는 전력선 위상 측정을 위해 A/D 변환기 및 위상계측 연산장치를 집적한 하이브리드 센서칩의 구현 기법을 제시하였다. 개발한 위상계측 연산장치는 recursive sliding-DFT에 기반하였으며 곱셈기의 시분할 공유 구조를 사용하여 칩의 구현 면적을 최소화 하였다. 60Hz의 전력선 신호를 중심주파수로 하는 AD 변환장치는 sigma-delta ADC를 기반으로 하여 8-bit 정밀도를 제공하며 아날로그부의 구현을 최소화하도륵 설계하였다. 설계한 하이브리드 센서칩은 컴퓨터 시뮬레이션 및 FPGA 구현을 통해 동작을 검증하였으며, 검증 완료후 $0.35{\mu}m$ CMOS 공정기술로 구현하였다. 전력선 위상을 측정하기 위해 구현된 4채널 하이브리드 센서 칩의 설계면적은 $5{\times}5m^2$ 의 약 20%정도를 차지하였다.

• Journal of IKEEE
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• v.23 no.4
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• pp.1182-1186
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• 2019

This paper discussed the research results on the development and output characteristics of single-phase direct drive 20W BLDC motor with ADC converter. It is designed to drive the rotor through PWM inverter switching and position the back electromotive force of the motor electrically 30° ahead of the hall sensor phase angle signal to ensure optimum switching time. As a major result of the characteristics evaluation, the maximum inverter efficiency was 92[%], the system efficiency was 53.34[%,] and the motor efficiency was 57.85[%].

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.444-448
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• 2006

In this paper, a frequency synthesizer for X-band FMCW radars is proposed. Some X-band FMCW radars have been used as a level sensor for tanker ship and the resolution of the level sensor may be mainly depend on linearity of frequency sweep. For a linear frequency sweep. the proposed synthesizer employs a phase-locked loop using prescalars and a high speed digital PLL chip. The measured results show that the linear frequency sweep range is from 10 GHz to 11 GHz and the output power of the synthesizer is minium 7 dBm. and the phase noise is about -80 dBc/Hz at 100 KHz offset from 11 GHz.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.105-113
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• 1997

We constructed a very accurate fiber bragg grating sensor system using an unbalanced mach-zehnder interferometer which converts the measurand-induced bragg wavelength shift to phase change of th einterference signal. With a shielded reference grating, output phase drift which orginates from the thermal drift on the interferometer was compensated. Mesured accuracy of the constructed system was 0.03 .deg. C and 0.26.mu. strain for temperature and strain measuremtn, respectively. It is over 300 times better resolution compared to the conventional optical spectrum analyzer which has 0.1nm wavelength resolution capability.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.19-29
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• 2008

Underwater acoustic(UWA) communication is one of the most difficult field in terms of severe channel environments such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of the image transmission using vertical sensor array instead of single sensor in the viewpoint of bit error rate(BER), constellation diagram, and received image quality.