• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.310-312
• /
• 2004

Generally, instrument transformer of the core type have been used for measuring current. Because instrument transformer has defects, electronic instrument was appeasred. This paper is introduced a basic concept and thoery of electronic instrument and described the the simulation of core type CT and no saturation CT. The evaluation of CT models implemented using EMTP(Electro Magnetic Transients Program) was carried out. The result of comparison both core type CT and no saturation CT are presented.

• Proceedings of the KSR Conference
• /
• 1999.11a
• /
• pp.360-367
• /
• 1999

An inverter-driven induction motor is used as the traction motor for a high speed drive system that required safety, reliabillity, performance, compact size owing to the space and weight alloted for attaching to train, etc. particularly it is possible to happen the saturation effects of flux density at constant voltage-frequency region and then increase very higher than the at lowed capacity of no-load current and temperature in any case. therefore the optimum design of core, optimum voltage-frequency ratio, adoption of high grade magnetic core have been developed and researched for preventing these problems. this paper show the saturation effects of traction rotor by measuring the induced voltage of search coil at stator teeth and presents optimum voltage-frequency ratio as well as optimum core design through the comparison with efficiency, power factor, load current and no-load current for korea high speed train.

• Agricultural and Biosystems Engineering
• /
• v.7 no.1
• /
• pp.8-12
• /
• 2006

This study was conducted to develop a real-time internal quality evaluation technique for Korean red ginseng using NIR spectroscopy while they were moving to be graded. Internal qualities of Korean red ginseng were defined by color, amount of white core and cavity in the red ginseng. To evaluate the internal quality, PLS (Partial Least Square) model was developed. Spectrum saturation can be occurred when most red ginseng has a sound internal quality expressed by higher light transmittance ratio, but that could not found in the ginseng of internal white core under the same light situation. And, if spectrum saturation is obtained, it is hard to identify the exact information of internal quality. In order to evaluate of the internal quality regardless of having internal normal core or white core, an integral time controlled method was used to obtain traditional spectrum. This procedure was applied in real-time process when red ginseng was moving to be graded in the line. Among the 450 samples including 223 internal normal ginsengs and 227 internal white core ginsengs, 315 ginsengs (70%) were used to develop a calibration model and 135 ginsengs were spent to validate the model. The result of quality evaluation by the model was very good showing SEP and bias were 0.3573 and 0.0310, respectively, and the accuracy was 95.6%.

• Journal of the Korean Geophysical Society
• /
• v.2 no.3
• /
• pp.225-233
• /
• 1999

Electrical resistivity of a rock-sample is dependant on not only formation factor of rock itself but also many parameters such as fluid type, measuring device, temperature, water saturation, electrical contact between electrode and core section, induced polarization, and frequency of electric source. In this study, we attempt to verify various affecting factors in core resistivity measurements and to find a better environment for core resistivity measurement. Particularly great attention has been paid to understanding the effects of temperature, water saturation, contact condition between sample and electrodes, and frequency of electric source. Precise measurement of resistivity can be achieved by utilizing silver paste for better contacts, taping samples for constant moisture contents, and using time-series resistivity data.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.57 no.3
• /
• pp.236-243
• /
• 2008

This paper analyses magnetic flux saturation of matching transformer considering characteristic of dynamic voltage restorer(DVR) system to solve voltage sags which are considered the dominant disturbances affecting power quality. This DVR consist of PWM inverter to inject arbitrary voltage, LC low pass filter and matching transformer for isolation and grid connection. However, the matching transformer has an excess of inrush current by magnetic flux saturation in the core of transformer. Due to this inrush current, the rating of matching transformers is double for needed nominal rating for protection of DVR. Therefore, in this paper, an advanced modeling method of magnetic flux saturation is used to analyze a magnitude and characteristic of magnetizing current. Simulation and experimental results considering characteristic of DVR system are provided to demonstrate the validity of the proposed analysis method.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.887.1_888.1
• /
• 2009

This paper proposes a core loss analysis method to obtain high accuracy prediction by using Multi-curve representing magnetic properties of a electrical steel in Finite Element Analysis (FEA). Generally, the magnetic prosperities of the electrical steel are measured by Epstein Method based on the international standards that are not good sufficient to predict motor performances. The method only aims to grade products in steel companies The magnetic properties of actual stator core is highly different to those given by steel companies due to the fact that stacking effect, shearing stress, nature anisotropy of electrical steels are not taken into account. In this paper, the magnetic properties are variously measured by three measuring devices, and then the several BH curves and BW curves obtained are used to analyze the core loss of a IPM. The BH curve in the high magnetic field are extrapolated using the mathematical formulation with the maximum saturation magnetic polarization measured

• Journal of Powder Materials
• /
• v.24 no.2
• /
• pp.122-127
• /
• 2017

Fe-6.5 wt.% Si alloys are widely known to have excellent soft magnetic properties such as high magnetic flux density, low coercivity, and low core loss at high frequency. In this work, disc-shaped preforms are prepared by spark plasma sintering at 1223 K after inert gas atomization of Fe-6.5 wt.% Si powders. Fe-6.5 wt.% Si sheets are rolled by a powder hot-rolling process without cracking, and their microstructure and soft magnetic properties are investigated. The microstructure and magnetic properties (saturation magnetization and core loss) of the hot-rolled Fe-6.5 wt.% Si sheets are examined by scanning electron microscopy, electron backscatter diffraction, vibration sample magnetometry, and AC B-H analysis. The Fe-6.5 wt.% Si sheet rolled at a total reduction ratio of 80% exhibits good soft magnetic properties such as a saturation magnetization of 1.74 T and core loss ($W_{5/1000}$) of 30.7 W/kg. This result is caused by an increase in the electrical resistivity resulting from an increased particle boundary density and the oxide layers between the primary particle boundaries.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.560-563
• /
• 2006

LED is promising for the application of specialty illumination. Thiscolor management system, V-core, with LED light sources and the structure of V-core for LCoS projector has been proposed to improve the primary saturation, uniformity and contrast. We designed the high efficient LED modules for high brightness requirement. The LED module can operate in narrow-direction indicator, $12^{\circ}$.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.14-15
• /
• 2006

A saturation of magnetic flux in the core may occur when a large primary current flows when the iron-cored current transformer is used. This saturation makes the distorted secondary current of the CT. the distorted secondary current may cause the mal-operation or operation time delay of protective relays. CT compensation algorithm using The LSQ(Least Square) fitting method has a problem. It needs to acquire enough data for executing this algorithm without an error. In this paper, an enhanced algorithm using interpolation based LSQ(Least Square) Fitting Method is proposed. The Lagrange Interpolation Method is used for the interpolation and CT is simulated by EMTP. The results show that the proposed algorithm can accurately compensate a distorted secondary current more than existing Algorithm when the saturation severely occurs.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.45 no.4
• /
• pp.490-500
• /
• 1996

The conventional method to deal with current transformer (CT) Saturation is over dimensioning of the core so that CTs can carry up to 20 times the rated current without exceeding 10% ratio correction. However, this not only reduces the sensitivity of relays as some errors may still be present in the secondary current when a severe fault occurs, but also increases the CT size. This paper presents an algorithm for compensating the distorted secondary current of iron-cored CTs under CT saturation using the magnetization (flux-current : .lambda.-i) curve and its performance is examined for fault currents encountered on a typical 345[kV] Korean transmission system, under a variety of different system and fault conditions. In addition, the results of hardware implementation of the algorithm using a TMS320C10 digital signal processor are also presented. The proposed algorithm can improve the sensitivity of relays to low level internal faults, maximize the stability of relays for external faults, and reduce the required CT core cross-section significantly. (author). refs., figs.