• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.255-263
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• 2010

The compensated-current-differential relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. Delta winding current is necessary to obtain the modified differential current for a $Y-\Delta$ transformer. This paper describes an estimation algorithm of the delta winding current and its application to a compensated-current-differential relay for a $Y-\Delta$ transformer. Prior to saturation, the core-loss current is calculated and used to modify the differential current. When the core first enters saturation, the initial value of the core flux is obtained by inserting the modified differential current into the magnetization curve. This flux value is used to derive the magnetizing current and consequently the modified differential current. The operating performance of the proposed relay was compared against a conventional current differential relay with harmonic blocking. Test results indicate that the proposed relay remained stable during severe magnetic inrush and over-excitation, and its operating time is significantly faster than a conventional relay. The relay is unaffected by the level of remanent flux and does not require an additional restraining or blocking signal to maintain stability. This paper concludes by implementing the proposed algorithm into a prototype relay based on a digital signal processor.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.17-20
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• 2015

Coated conductor is an important candidate for power cable applications due to its high current density. Even for DC power cable transmission, we must study the transport properties of HTS tapes after slow and fast discharge. In order to evaluate relation of the magnetic field with applied current we developed a scanning magnetic field measurements system by employing a Hall probe. This work presents the measurements of the magnetic fields above a coated conductor by varying applied current pattern. In the work, a transport current of 100 A, less than the critical current, is applied to YBCO coated conductor. We measured the residual magnetic field distributions after cut off the transport current with slow and fast operations. The results show differences of the magnetic field profiles and the corresponding current profiles by an inverse solution from the magnetic field measurement between these two operations because of the hysteresis of coated conductor excited by the transport current.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.114-116
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• 1994

Recently a superconducting fault current limiter(SFCL) has public attentions for the solution of large fault currents of power systems. Though a SFCL has more effective characteristics than the other current limiting devices, there are many problems to apply it to real power systems. For the analysis of transient fault characteristics of the SFCL, we designed and fabricated a inductive SFCL and tested it in 35V line. The superconducting cable of the SFCL was quenched at lower current(49A) than the designed critical current but it limited the fault current to the lower value(150A) than the one expected without SFCL(250A). And within one period the fault current decreased lower than normal laod current.

• The Korean Journal of Physiology
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• 제28권2호
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• pp.143-150
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• 1994

The whole-cell mode of the patch clamp technique was used to study $Ca^{2+}-activated\;Cl^-\;current$ $(I_{Cl_{Ca}})$ in gastric antral myocytes. Extracellular application of caffeine evoked $Ca^{2+}-activated\;current$. In order to isolate the chloride current from background current, all known systems were blocked with specific blockers. The current-voltage relationship of caffeine-induced current showed outward rectification and it reversed at around $E_{Cl^-}$. The shift of reversal potential upon the alteration of external and internal chloride concentrations was well fitted with results which were calculated by the Nernst equation. Extracellular addition of N-phenylanthranilic acid and niflumic acid which are known anion channel blockers abolished the caffeine induced current. Intracellular application of a high concentration of EGTA also abolished this current. Application of c-AMP, c-GMP, heparin, or $AIF^-_4$ made no remarkable changes to this current. Sodium replacement with the impermeable cation N-methylglucamine or with $Cd^{2+}$ rarely affected this current. From the above results it is suggested that the caffeine induced current was a $Cl^-$ current and it was activated by intracellular $Ca^{2+}$.

• Progress in Superconductivity
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• 제11권1호
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• pp.19-24
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• 2009

Among the various types of fault current limiters, superconducting fault current limiters could be the most preferable choice for high voltage electric power systems owing to the remarkable current limiting characteristics of superconductors. But, there have been no commercial superconducting fault current limiters which were installed into actual electric power systems until these days due to some remained technical and economical problems. Thus, in order to promote the development and application of the superconducting fault current limiters into real field, it is essential to understand the power utilities’ requirements for their networks and also suitable test method and some specifications should be prepared. This paper focuses on the matters of test requirements and standardization issues that should be prepared for commercialization of superconducting fault current limiters. The unique current limiting characteristics of superconducting fault current limiters were investigated and related other standards including circuit breakers, transformers, reactors, power fuse, and fused circuit breakers were compared to setup the basis of novel specification of superconducting fault current limiters. Furthermore, required essential test procedures for superconducting fault current limiters were suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.539-541
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• 1994

The average current mode control of zero current switched series resonant converter is proposed. The conventional current controllers such as bang bang current controller and predictive current cantroller have some demerits like current offset and complexity. In this paper, the proposed current control technique are conventional current control techniques are comparatively studied. By the proposed control technique. the current cantroller can be simplely implemented without current offset.

• Journal of information and communication convergence engineering
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• 제18권3호
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• pp.201-206
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• 2020

This paper presents a new method for controlling the current of lighting LEDs without current sensors. This method can be used as backup against LED current sensor faults. LED lighting requires a circuit with a constant current in order to maintain the same brightness when the ambient temperature changes. Therefore, we propose a new current estimation method to provide backup in case of current sensor faults based on the calculation of the inductor current. In the fabricated circuit, the average current changes from 144.03 mA to 155.97 mA when the ambient temperature changes from 0℃ to 60℃. The application of this study can enable the fabrication of a driving IC for LEDs in the form of a single chip without sensing resistors. This is expected to reduce the complexity of the peripheral circuit and enable precise feedback control.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.294-298
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• 2003

In this paper, the new zero-current-transition (ZCT) circuit cell is proposed. The main switch is turned-off under the zero current and zero voltage condition, and there is no additional current stress and voltage stress in, the main switch and the main diode. The Auxiliary switch is turned-off under the zero voltage condition, and the main diode is turned-on under the zero voltage condition, The resonant current required to obtain the ZCT is small and regenerated to the input voltage source. The operational principles of the boost converter integrated with the proposed ZCT circuit cell is analyzed theoretically and verified by the simulation and experimental result. Index terms - zero-current-transition (ZCT), zero-current- switching (ZCS), zero-voltage-switching (ZVS)

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.318-318
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• 2000

Current signal square based on switch current is presented in this article. This is the new technique that can design current signal square circuit by using switch-current memory cell, current square and sample and hold technique, which have been presented by the general switch-current. This principle which is present have the good electrical characteristics such as the low input impedance, high output impedance and high frequency response. The system can also operate in the audio frequency range to the high frequency current signal. The system application of this technique can be apply to the current signal multiplier by quarter square technique. The experimental results agree well with the theory as high accuracy and linearity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.886-888
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• 1993

Recently current mode control is widely adopted in switching power converter because of inherent stablity and ability of parallel operating. There are several ways in current mode control. One of them, peak current control is chiefly employed. Peak current mode control converter usually senses and controls peak inductor current. But there is peak-to-average current errors. Therefore peak current control needs compensation ramp correcting the errors. Average current mode control eliminates these problems, and is constructed by simple structures. This paper will describe the behavior of a simple average current mode boost converter and introduce the design techniques.