• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권5호
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• pp.238-245
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• 2001

During an AC motor's start-up accelerating period, a large amount of current is required to reach to the rating speed. This is called in-rush current. This peak in-rush current can be more than about several times the operating or steady-state current in the full load rating of the motor. In-rush current is present in both and electronic ballasts. The main area of concern is the tripping of circuit breaker and fuses which can affect electrical system components From this, we can see that the electrical power controllers will be rather concerned, since they have to supply the actual current necessary to start the motor. This paper presents a new method to reducing in-rush current and energy saving of the single-phase induction motor used in air-conditioner. It can be obtained that proposed system is low cost and small size as compared with other controller. Experiments are focused on a capacitor starting single-phase induction motor. The optimal power saving and in-rush current limiting by phase angle control are verified by experimental results. Also, auxiliary winding was controlled by electronic starting switch.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1058-1062
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• 2000

We investigated resistive superconducting fault current limites (SFCLs) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 A$\_$peak/, was produced and successfully tested at a 220 V$\_$rms/circuit. From the resistance increase, we estimated that the film temperature increased to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V$\_$rms/.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.523-526
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• 2004

According to the continuous demand for power and the growth of electric power utilities, the electric power transmission capacity was increased. The increase of the electric power transmission capacity results in an increase of the fault current level a fault happened. So the superconducting fault current limiter(SFCL) has been reached as the countermeasure for the reduction of the fault current. In this paper, we investigate the fault currents characteristics of resistive type SFCL according to fault angles when AC power source applied. As the fault angles increase, the first peak value of fault current decreased lower. On the other hand, the power burden of SFCL increased.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.525-527
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• 1996

Hysteresis current control is one of the simplest techniques used to control currents for high speed drive systems, because of its simplicity of implementation, fast current control response, and inherent peak current limiting capability. However the conventional fixed-band hysteresis control has a variable switching frequency throughout the fundamental period, and consequently the load current harmonics spreaded on the wide frequency range. In this paper, a simple, novel alterative approach is proposed for a variable-hysteresis band current controller which uses feedback techniques to achieve constant switching frequency with good dynamic response. The method is easily implemented in hardware, the resultant controller is easily tuned to a particular load, and has good immunity to variation in PV parameter and dc supply voltage.

• 대한화학회지
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• 제15권6호
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• pp.347-352
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• 1971

The variations of the positive and negative electrode potentials, and of internal pressure were measured during the charge of the sealed type Ni-Cd cell. Both polarization characteristics of a paste type Cd-electrode as a gas diffusion electrode in 30% KOH solution and the effects of active carbon electrode as an oxygen consuming auxiliary electrode of the Ni-Cd cell on the charging characteristics of the cell were studied. Peak voltage at the end of charge of the cell is ascribed to the peak at the negative electrode potential, which is due to the concentration polarization by the lack of $Cd^{++}$ ion and oxygen concentration. And the recovery of the negative electrode potential is resulted from depolarization by the increasing diffusion limiting current density with the increasing oxygen pressure. The active carbon electrode was effective as an oxygen consuming auxiliary electrode. The internal pressure of the cell could be maintained below 200mmHg even at one hour rate charge and overcharge by the use of active carbon electrode as an auxiliary electrode.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.75-76
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• 2016

This paper proposes a power factor correction circuit with a high efficiency over a wide load range characteristics for a communication power supply. And the characteristic verification is applied to produce a design of prototype. Power factor correction circuit can reduce conduction losses by applying Bridgeless Boost Converter for efficiency. Over a wide load range to maintain the efficient, the control method of a PWM controller is divided by two sections according to the load area. In the low-load region, it was reduced switching losses by applying the critical conduction mode control method. On the other hand, in the heavy-load area, the hysteresis current control method is used to maintain the high efficiency over a wide load range by limiting the peak noise of the inductor.

• The Korean Journal of Physiology and Pharmacology
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• 제5권6호
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• pp.487-494
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• 2001

During depolarization, extrusion of $Ca^{2+}$ from sarcoplasmic reticulum through forward-mode $Na^+-Ca^{2+}$ exchange was studied in the rat ventricular myocytes patch-clamped in whole-cell configuration. In order to confine the $Ca^{2+}$ responses in a micro-domain by limiting the $Ca^{2+}$ diffusion time, rat ventricular myocytes were dialyzed with high (14 mM) EGTA. $K^+$ current was suppressed by substituting KCl with 105 mM CsCl and 20 mM TEA in the pipette filling solution and by omitting KCl in the external Tyrode solution. $Cl^-$ current was suppressed by adding 0.1 mM DIDS in the external Tyrode solution. During stimulation roughly mimicking action potential, the initial outward current was converted into inward current, $47{\pm}1%$ of which was suppressed by 0.1 mM $CdCl_2.$ 10 mM caffeine increased the remaining inward current after $CdCl_2$ in a cAMP-dependent manner. This caffeine-induced inward current was blocked by $1\;{\mu}M$ ryanodine, $10\;{\mu}M$ thapsigargin, 5 mM $NiCl_2,$ or by $Na^+\;and\;Ca^{2+}$ omission, but not by $0.1\;{\mu}M$ isoproterenol. The $I{\sim}V$ relationship of the caffeine-induced current elicited inward current from -45 mV to +3 mV with the peak at -25 mV. Taken together, it is concluded that, during activation of the rat ventricular myocyte, forward-mode $Na^+-Ca^{2+}$ exchange extrudes a fraction of $Ca^{2+}$ released from sarcoplasmic reticulum mainly by voltage-sensitive release mechanism in a micro-domain in the t-tubule, which is functionally separable from global $Ca^{2+}{_i}$ by EGTA.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권10호
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• pp.537-543
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• 1999

We fabricated a resistive superconducting fault current limiter (SFCL) of a meander type based on a YBCO film with the meander cross section of 5 $\times$ $10^{-6}$$cm^2$, and performed current limitation experiments. The film was coated quench current was 9.6 Apeak at 60 Hz, and the fast quench time was 0.63 msec. The resistance of the limiter continuously increased for three cycles dut to the temperature rise in the gold layer. The temperature of the current limiting element reached the room temperature in 11 msec, $150^{\circ}C$ in 54 msec after quench, and was saturated afterwards. For $45^{\circ}$and $90^{\circ}$faults the fast quench times were 0.56 msec and 0.26 msec, respectively. The quench time is believed to be reduced because the fault occurred when the current was either increasing or at the peak value. This limiter effectively limited the fault current to about 1/5 of the potential current with no SFCL right after the fault and to about 1/8.5 in three cycles. We confirmed that the gold layer effectively carried out the role of heat dissipation as the SFCL was quenched.

• 조명전기설비학회논문지
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• 제23권10호
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• pp.14-20
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• 2009

전력 계통 내에서 발생하는 과도한 고장전류의 억제를 위한 가장 이상적인 방안은 초전도 한류기이다. 초전도 한류기의 전력계통 적용을 위해 본 논문에서는 전력계통 내에서 발생하는 1선, 2선, 3선 지락사고를 모의하여 매트릭스형 초전도 한류기의 동작 특성 및 소비전력을 분석하였다. 모든 지락사고에 대해 매트릭스형 초전도 한류기는 사고 초기에는 85[%] 이상, 1주기 이후에는 95[%] 이상 고장전류를 제한시킬 수 있다는 것을 확인하였다. 또한 초전도 소자간의 임계특성의 차이를 줄여줌으로써 소비전력이 균등해진다는 것을 확인하였다.

• 조명전기설비학회논문지
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• 제20권7호
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• pp.38-45
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• 2006

초전도전류제한기(SFCL)는 전력계통내 적용시 계통보호를 보다 향상시킬 수 있는 방안으로써 수초이내에 신속하게 사고전류를 제한한다. 이러한 SFCL중 자속구속형 전류제한기의 설계구조는 자속구속리액터인 하나의 철심에 1차측과 2차측 코일이 병렬로 결선되어 있다. 또한 전류제한소자인 YBCO박막과 2차측 코일을 직렬로 결선하여 설치장소의 조건에 따라 인덕턴스와 2차측 코일의 극성방향으로 과도전류 크기를 조절할 수 있다. 이러한 동작특성은 철심을 자속매개체로 적용되기 때문에 철심조건에 따른 성능평가실험은 필수적이다. 가극결선에서 전원전압을 200[Vrms] 인가시 피크전류는 폐루프가 30.71[A], 개루프가 32.01[A]까지 상승됨에 따라 초기과도 응답특성은 폐루프가 유리하였다. 하지만, 소자에 발생되는 전압이 폐루프가 220.14[V], 개루프가 142.73[V]까지 상승함에 따라, 폐루프 철심구조시 전류제한소자의 부담이 가중됨을 알 수 있었다. 결과적으로 자속구속형 SFCL의 전력계통내 적용 시 각각의 철심구조에 따른 다양한 운전특성을 적절히 설계시 장점을 극대화 할 수 있을 것이다.