• Progress in Superconductivity and Cryogenics
• /
• v.13 no.3
• /
• pp.10-13
• /
• 2011

The power demand is steadily increasing due to rapidly develop of industrial field. The ratio of prospected increment of power consumption is over 2.2 % per year from 2007 to 2020 year. The superconducting fault current limiters(SFCLs) should be suggested to be one of promising machines to protect power grid. Four basis tests such as resistivity, short-circuit tests, ac losses and recovery time were investigated according to various reached maximum temperature, operating temperature. This paper deals with investigation of the various commercial high temperature superconductor for applying resistive type SFCLs.

• Electrical & Electronic Materials
• /
• v.9 no.9
• /
• pp.891-899
• /
• 1996

A model for predicting the characteristics of elastic ferromagnetic materials having a moving gap was presented. Based on the model parameters concerning behavior of material, such as the instantaneous field intensity, attractive force between the poles, length of gap, and the induced current/ emf in the circuit can be determined from the numerical integrations of the governing equations derived. From the results of the model it is found that when dc emf is imposed on the circuit the current sharply rise and fall for very short duration then stabilize at extremely low level which depends mainly on elasticity, permeabilities and ratio of resistivity. Subsequently output emf is shown stabilized at constant value which depends on the previous parameters as well as the resistivity ratio of primary to secondary circuit after sufficient progress of time.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.12
• /
• pp.24-30
• /
• 2003

In this paper, we proposed an adaptive ATC(Automatic Threshold Control) circuit with more decreased settling time by improving the structure of the peak detector. We showed that it could reduce a good deal of the settling time because it showed less than half the error voltage ratio that the ATC circuit with conventional structure showed in analysis. We also designed a burst-mode ATC circuit for the 1.25Gbps EPON system using a commercial foundry. It produced the reference levels in very short time, 6㎱ in 40 ㏈ input dynamic range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.4
• /
• pp.374-380
• /
• 2007

In this paper a nobel optimum design method is presented for a shield in a vacuum interrupter which is equipped in switchgear to improve its electric insulation capability. The design of Taguchi experiment method which is based on the results by finite element method is used to find optimum design conditions. The important design factors are chosen at first and the concept of signal to noise ratio is applied to evaluate the vacuum interrupter performance, and the optimal values of each parameters are determined. From the results of various analyses, it is shown that the shield plate in circuit circuit breaker compartment of switchgear can reduce the concentration of electric field intensity. This method is very useful to design the construction of a shield in a short time. Consequently, the insulation capability of circuit breaker compartment in a gas insulated switchgear is improved by adopting an additional optimized shaped shield.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.3
• /
• pp.246-251
• /
• 2013

Screen printing is commonly used to form the front/back electrodes in silicon solar cell. But it has caused high resistance and low aspect ratio, resulting in decreased conversion efficiency in solar cell. Recently the plating method has been combined with screen-printed c-Si solar cell to reduce the resistance and improve the aspect ratio. In this paper, we investigated the effect of light induced silver plating with screen-printed c-Si solar cells and compared their electrical properties. All wafers were textured, doped, and coated with anti-reflection layer. The metallization process was carried out with screen-printing, followed by co-fired. Then we performed light induced Ag plating by changing the plating time in the range of 20 sec~5min with/without external light. For comparison, we measured the light I-V characteristics and electrode width by optical microscope. During plating, silver ions fill the porous structure established in rapid silver particle sintering during co-firing step, which results in resistance decrease and efficiency improvement. The plating rate was increased in presence of light lamp, resulting in widening the electrode with and reducing the short-circuit current by shadowing loss. With the optimized plating condition, the conversion efficiency of solar cells was increased by 0.4% due to decreased series resistance. Finally we obtained the short-circuit current of 8.66 A, open-circuit voltage of 0.632 V, fill factor of 78.2%, and efficiency of 17.8% on a silicon solar cell.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.2
• /
• pp.119-126
• /
• 1999

Current transformer (CT) saturation may cause a variety of protective relays to malfunction. The conventional CT is designed that it can carry up to 20 times the rated current without exceeding 10% ratio error. However, the possibility of CT saturation still remains if the fault current contains substantial amounts of ac and/or dc components. This paper presents a design method of iron-cored CTs for use with protective relays to prevent CT saturation. The proposed design method determines the core cross section of the CT; it employs the transient dimensioning factor to consider relay's operating time (duty cycle) and dc component as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider the biggest fault current. The method designs the cross section of CTs in cases of reclosure and no reclosure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.5
• /
• pp.410-415
• /
• 2011

In this paper, we investigated the fault current limiting and the load voltage sag suppressing characteristics of the flux-lock type SFCL, designed with the additive polarity winding, according to the variations of turn number's ratio and the comparative analysis between the resistive type and the flux-lock type SFCLs were performed as well. From the analysis for the short-circuit tests, the flux-lock type SFCL designed with the larger turn number's ratio was shown to perform more effective fault current limiting and load voltage sag suppressing operations compared to the flux-lock type SFCL designed with the lower turn number's ratio through the fast quench occurrence of the high-$T_C$ superconducting (HTSC) element comprising the flux-lock type SFCL. In addition, the recovery time of the flux-lock type SFCL after the fault removed could be confirmed to be shorter in case of the flux-lock type SFCL designed with the lower turn number ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.11
• /
• pp.995-999
• /
• 2007

We investigated the characteristics of a flux-lock type superconducting fault current limiter(SFCL) considering magnetization characteristic of iron core. The flux-lock type SFCL, like other types of SFCLs using the iron core, undergoes the saturation of the iron core during the initial fault time. Therefore, if the design to prevent the saturation of the iron core is considered, the effective fault current limiting operation can be achieved. Through the analysis for its equivalent circuit including the magnetization characteristic of the iron core, the limiting impedance of the flux-lock type SFCL was drawn. The magnetization currents and the limited currents of SFCL, which were dependent on the winding direction and the turns' ratio between two coils, were investigated from the short circuit experiment. It was confirmed that their experimental results agreed with the analysis ones.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1110-1111
• /
• 2008

The life time of PV module is semi-permanent. But, because of installation and module fabrication process, its important part can not be finished. In this paper, we analyze 15 years old modules made from different company. Among the PV modules, the maximum power drop ratio was 12.23% minimum and 80.63% maximum. Also the effect of solar cell's short circuit current difference was analyzed. The PV module exposed about 65days, its the maximum power drop ratio was 1.29% minimum and 23.43% maximum. It is for reduction of current value. And the reason for current reduction was due to reduction of parallel resistance of solar cell. To prevent early degradation, it is need to have attention to fabrication, installation and maintenance.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.535-538
• /
• 1994

In this paper, an isolated ZVS-PWM boost converter is proposed for single stage line conversion. For power factor correction, we used the half bridge topology at the primary side of isolation transformer permitting switching devices to operate under ZVS by using circuit parastics and operating at a fixed duty ratio near 50%. Thus the relatively continuous input current distortion and small size input filter are also achievable. The ZVS-PWM boost operation of the proposed converter can be achieved by using the boost inductor $L_f$, main switch $Q_3$, and simple auxiliary circuit at the secondary side of isolation transformer. The secondary side circuit differ from a conventional PWM boost converter by introduction a simple auxiliary circuit. The auxiliary circuit is actived only during a short switching transition time to create the ZVS condition for the main switch as that of the ZVT-PWM boost converter. With a single stage, it is possible to achieve a sinusoidal line current at unity power factor as well as the isolated 48V DC output. Comparing to the two stage schemes, overall effiency of the proposed converter is highly improved due to the effective ZVS of all devices as well as single stage power conversion. Thus, it can be operated at high switching frequency allowing use of small size input filter. Minimum voltage and current stress make it high power application possible.