• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.8
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• pp.8-21
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• 1997

In this paper, we consider resistive shorts on gate-source, gate-drain, and drain-source as well as opens in MOS FETs included in typical memory cell of VLSI SRAM and analyze behavior of memory by using PSPICE simulation. Using conventional fault models and this behavioral analysis, we propose linear testing algorithm of complexity O(N) which can be applied to both functional testing and IDDQ (quiescent power supply current) testing simultaneously to improve functionality and reliability of memory. Finally, we implement BIST (built-in self tsst) circuit and BICS(built-in current sensor), which are embedded on memory chip, to carry out functional testing efficiently and to detect various defects at high-speed respectively.

• Progress in Superconductivity and Cryogenics
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• v.8 no.2
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• pp.20-24
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• 2006

Recently, utility network is becoming more and more complicated and huge due to IT and OA devices. In addition to, demands of power conversion devices which have non-linear switching devices are getting more and more increased. Consequently, because of the non-linear power semiconductor devices, current harmonics are unavoidable. Sometimes those current harmonics flow back to utility network and become one of the main reasons which can make the voltage distortion. Also, it makes noise and heat loss. On the other hands, voltage sag from sudden increasing loads is also one of the terrible problems inside of utility network. In order to compensate the current harmonics and voltage sag problem, AF(active filter) systems could be a good solution method. SMES is a very good promising source due to it's high response time of charge and discharge. Therefore, the combined AF and SMES system can be a wonderful device to compensate both harmonics current and voltage sag. However, SMES needs a superconducting magnetic coil. Because of using this superconducting magnetic coil, quench problem caused by unexpected reasons have always been unavoidable. Therefore, to solve out mentioned above, this paper presents a decisive method using shunt and series active filter system combined with SMES. Especially, authors analyzed the change of original energy capacity of SMES regarding to the size of resistance caused by quench of superconducting magnetic coil.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.544-558
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• 2013

This paper proposes a simplified and efficient control scheme for Unified Power Quality Conditioner (UPQC) based on three-level (NPC) inverter capable to mitigate source current harmonics and compensate all voltage disturbances perturbations such us, voltage sags, swells, unbalances and harmonics. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. The shunt and series AF are designed using a three-phase three-level (NPC) inverter. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt and the power reactive theory (PQ) for a series APFs. The reference signals for the shunt and series APF are derived from the control algorithm and sensed signals are injected in tow controllers to generate switching signals for series and shunt APFs. The performance of proposed UPQC system is evaluated in terms of power factor correction and mitigation of voltage, current harmonics and all voltage disturbances compensation in three-phase, three-wire power system using MATLAB-Simulink software and SimPowerSystem Toolbox. The simulation results demonstrate that the proposed UPQC system can improve the power quality at the common connection point of the non-linear load.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.43-47
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• 2012

A linear compressor generates pulsating pressure and oscillating flow in a cryocooler such as Stirling cryocooler and pulse tube refrigerator. It is driven by AC power source and designed to operate at resonance of piston motion. The driving voltage level is determined by electric parameters of resistance, inductance and thrust constant of linear motor. From voltage equation on linear motor, the power factor of driving power is inherently less than 1. The phase difference between voltage and current of supplied power can be zero using capacitor and this can minimize a supply voltage level. Especially, the linear compressor of kW class requires high voltage and thus can cause a difficulty in selecting power supply unit due to limitation of voltage level. The capacitor in driving electric circuit is useful to settle this problem. In this study, the electric circuit of linear compressor is analytically investigated with assumption of mechanical resonance. The electric parameters of commercial linear motor are used in the analysis. The effects of capacitor on driving voltage level and power factor are investigated. From analytic results, it is shown that the voltage level can be mimized with using capacitor in driving electric circuit.

• Tribology and Lubricants
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• v.11 no.1
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• pp.20-26
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• 1995

Most magnetic bearings are based on the attractive force between the magnets and ferrous materials. One of the disadvantages of such attractive type magnetic bearings is the instability so that an active control device is necessary to operate bearing successfully. In this study a repulsive type magnetic bearing is analyzed which uses eddy current as a force source. The load capacities are analyzed for the various gap sizes, the rotor velocities and the frequencies of current supplied to electromagnet. Analytic Results show that as the gap size decreases, the levitation and drag forces increase, while the number of poles increasqs, the drag force decreases in the higher linear velocity region. Experimental results show that as the gap size decreases the levitation and the drag force increase, and as the velocity of rotor increases, the drag is larger than the levitation force up to certain velocity. But after that, the levitation is larger than the drag force. As the frequency of the current increases the levitation and drag decreases while the thickness of rotor gets thicker the forces decrease because of increase in eddy current loss.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.202-207
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• 1997

Design and fabrication issues for an L-band GaAs Monolithic Microwave Integrated Circuit(MMIC) Voltage Controlled Oscillator(VCO) as a component of Personal Communications Systems(PCS) Radio Frequency(RF) transceiver are discussed. An ion-implanted GaAs MESFET tailored toward low current and low noise with 0.5mm gate length and 300mm gate width has been used as an active device, while an FET with the drain shorted to the source has been used as the voltage variable capacitor. The principal design was based on a self-biased FET with capacitive feedback. A tuning range of 140MHz and 58MHz has been obtained by 3V change for a 600mm and a 300mm devices, respectively. The oscillator output power was 6.5dBm wth 14mA DC current supply at 3.6V. The phase noise without any buffer or PLL was 93dB/1Hz at 100KHz offset. Harmonic balance analysis was used for the non-linear simulation after a linear simulation. All layout induced parasitics were incorporated into the simulation with EEFET2 non-linear FET model. The fabricated circuits were measured using a coplanar-type probe for bare chips and test jigs with ceramic packages.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.394-397
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• 2014

This paper deals with the comparison and dynamic behavior of a moving-coil linear oscillatory actuator (MCLOA) with/without a mechanical spring. On the basis of a dynamic simulation model, the dynamic characteristics such as a current and a stroke of the MCLOA without the spring are predicted for various values of frequency. And then, dynamic test results are given to confirm the dynamic simulations. Finally, this paper describes the influence of the spring on the dynamic behavior of the MCLOA from the dynamic experiments of the MCLOA with/without the spring.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.894-901
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• 1991

Contact-type linear image sensors have been fabricated by means of RF glow discharge decomposition method of silane and hydrogen mixtures. The dependences of the electrical and optical properties of these sensor on thickness, RF power, substrate temperature and ambient gas pressure have been investigated. the ITO/i-a-Si:H/Al structure film shows photosensitivity of 0.85 and photocurrent to dark current ratio ($I_{ph}/I_{d}$) of 150 at 5V bias voltage under 200${\mu}W/cm^[2}$ red light intensity. Under 200${\mu}W/cm^[2}$ green light intensity, the ratio is 100. In order to investigate photocarrier transport mechanism and to obtain ${\mu}{\gamma}$ product we have measured the I-V characteristics of these sensors favricated with several different deposition parameters under various light sources. The linear inage sensor for document reading has been operated under reverse bias condition with green light source, resulting in ${\mu}{\gamma}$ product of about 1.5$[\times}10^{-9}cm^{2}$/V.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.254-255
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• 2013

In this paper, four switches three-phase Z-source dynamic harmonic filter is proposed. It has many advantages, such as reduction of the cost, switching loss and smaller drive circuit. In order to reduction harmonics, new PWM modulation technique with a variable index has been suggested that in comparison with a fixed index type has more capability. The paper presents an application of direct current control(DCC) method in Z-source dynamic harmonic filter to reduce the harmonics generated by the non-linear load. The experimental results will verify the validity of the proposed method.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.290-301
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• 2006

A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank. Efficiency of push pull hood system is affected by various parameters, such as, cross draft, vessel shapes, tank surface area, liquid temperature. A previous work assisted by flow visualization technique qualitatively showed that a strong cross draft blown from the pull hood to push slot could destroy a stable wall-jet on the surface of tank, resulting in the abrupt escape of smoke from the surface. In this study, the tracer gas method was applied to determine the effect of cross-draft on the capture efficiency qualitatively. A new concept of capture efficiency was introduced, that is, linear efficiency. This can be determined by measuring the mass of tracer gas in the duct of pull hood while the linear tracer source is in between push slot and pull hood. By traversing the linear tracer source from the push slot to the pull hood, it can be found where the contaminant is escaped from the tank. Total capture efficiency can be determined by averaging the linear efficiencies. Under the condition of cross-draft velocities of 0, 0.4, 0.75, 1.05 and 1.47m/s, total capture efficiencies were measured as 97.6, 95.4, 94.6, 92.7 and 70.5% respectively. The abrupt reduction of efficiency with cross-draft velocity of 1.47m/s was due to the destruction of tank surface wall-jet by the counter-current cross-draft. The same phenomenon was observed in the previous flow visualization study. As an alternative to overcome this abrupt efficiency drop, the 20% increase of hood flow rates was tested, resulting in 20% efficiency increase.