• Journal of Power Electronics
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• 제17권6호
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• pp.1480-1489
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• 2017

In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

• 전자공학회논문지
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• 제49권11호
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• pp.193-198
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• 2012

LED를 고효율 및 고수명으로 동작시키기 위해 장착되는 LED 컨버터는 정전압 및 정전류 구동을 함으로서 LED에 제공되는 전력을 일정한 전압과 전류 값으로 유지하여 LED를 동작시키게 한다. 하지만 이러한 LED 컨버터는 LED의 과열로 인해 전압이 떨어지거나 전력 선로의 손상으로 인한 과전압 혹은 회로 이상에 따른 과전압 발생 시에도 여전히 일정 전압 및 전류를 계속 LED에 공급하게 된다. 결국 LED에 과도한 전압이나 전류가 유입되어도 LED는 계속적으로 발광하기에 결국 파손되는 문제가 발생하게 된다. 본 논문에서는 LED의 과열이나 전압강하 등의 이유로 과전류가 발생하면 PWM 회로를 정지시키고 일정 전류 이하에서만 PWM 회로가 동작하도록 하며 PWM 회로에서 과전압이 발생되는 경우 회로의 구동을 일시 정지시켜 LED가 과전류와 과전압에 의해 파손되는 것을 방지하는 피드백 회로를 제안한다.

• 전기의세계
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• 제17권3호
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• pp.7-28
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• 1968

When a insulator plate is inserted to the discharge path of a space discharge gap in which the field strength is not uniform, the spark voltage under the atmospheric pressure between the electrodes decreases or rises according to the position of the insulating plate. Also it is reported that if a metallic barrier plate is inserted to the discharge path of the same space discharge gap, similar variations of spark voltage are found. Speaking briefly, mensioned above are the spark voltage characteristics when an insulator or metallic barrier is inserted to the space discharge gap. Also some experimental results, concerning to the surface creepage flash over characteristics at the case when an insulator barrier is inserted to the discharge path of a surface creepage discharge gap, were reported by Peek. But up to now there are no reports on surface flash over voltage characteristics at the case when a metallic barrier is inserted to the surface creepage gap. In this study the effects of a conducting metallic barrier inserted to the path of a surface creepage discharge gap on the flash over voltage characteristics are investigated theoretically and experimentally, and got some important results, clearing the effects of the position and width of a conducting barrier is inserted, the surface flash over voltage characteristics appear as an Inverse N or W Characteristics. Such theoretical or experimental results may have some relation not only with the effects of dry belt and snow on suspension insulators, but also with the effects of dirty zone or water drops on the surface creepage flash over voltage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.65-70
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• 1999

In this paper, the cost-effective design of output reactor which is used to suppress the over-voltage at the motor terminal in the Adjustable Speed Drives(ASD) application is proposed. In the elevator drive system, the power cable length is relatively shorter than other ASD applications and then the over-voltage at the motor terminal depends on the frequency characteristics of the output reactor at the over-voltage operating frequency. The over-voltage suppression mechanism of output reactor in ASD application is analyzed and the dominant parameters of output reactor for the over-voltage suppression are extracted. Using these parameters as the design values and considering the high frequency characteristics of iron core in the reactor, a new cost-effective structure of output reactor is proposed. Experimental results of the conventional reactor and the proposed reactor with a 15kW induction motor are given to verify the proposed scheme.

• 전자공학회논문지
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• 제53권11호
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• pp.107-113
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• 2016

전원입력단에 사용되는 회로는 입력전원만을 사용할 수가 있다. 일반적인 전자회로는 입력전원을 이용하는 전압변환기에 의해 생성되는 2차전원을 이용하게 된다. 하지만 전원입력단의 저전압 및 과전압에 의한 고장에 대비하기 위한 보호회로는 2차 전원을 사용할 수가 없기 때문에, 입력전원만을 이용해서 구현이 되어야 한다. MOS FET의 문턱전압 특성을 이용한 저전압/과정압 검출회로는 50V 입력전압만을 이용해서, 정상적인 전압범위를 벗어나는 저전압/과전압 현상을 정상적으로 검출할 수가 있고, 기존의 Zener diode만으로 보호만 가능했던 것을 검출이 가능하게 되었고, 이상전압검출회로의 동작의 정확도를 결정하는 기준전압은 환경조건 등에 의해서 발생할 수 있는 모든 변수를 고려하면 최악조건 해석상으로 8.4%에서 2.5%로 향상되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1536-1539
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• 1994

The influence due to metallic particle contaminated on spacer surface is remarkable in the decreasing of dielectric strength in $SF_6$ GIS. In relation with this problem, We studied, AC flash-over voltage characteristics and breakdown mechanism are investigated under metallic particle initiated condition in $SF_6$ gas by varying the particle position, particle shape with a plane-plane electrode. The main results arc as follows 1. The small amount of the metallic particle in the gap do not make flash-over voltage to be influence, but the significant decrease of th flash-overed voltage is result in case of the big and long size of the metallic paraticle. 2. Influence of the flash-over voltage are lowest in the mid and are highest in the electrode of metallic particle position. 3. In case of the initiated metallie particle, The more the pressure are high, the more the recluced ratio of flash-over voltage are high. 4. The metallic particle shape which results in the reduced flash-over voltage forced the critical pressure to move in to the region of low pressure. 5. The existance of the metallic particle on the upper electrode side and high pressure make the decreasing ratio of flash-over voltage bigger than that of the ground side electrode.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1752-1758
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• 2018

In a low-voltage distribution system, the molded case circuit breaker (MCCB) is a widely used device to protect loads by interrupting over-current; however the hot gas generated from the arc discharge in the interrupting process depletes the dielectric recovery strength between electrodes and leads to re-ignition after current-zero. Even though the circuit breaker is ordinarily tripped and successfully interrupts the over-current, the re-ignition causes the over-current to flow to the load again, which carries over the failure interruption. Therefore, it is necessary to understand the dielectric recovery process and the dielectric recovery voltage of the MCCB. To determine these characteristics, a measuring system comprised of the experimental circuit and source is implemented to apply controllable recovery voltage and over-current. By changing the controllable recovery voltage, in this work, re-ignition is driven repeatedly to obtain the dielectric recovery voltage V-t curve, which is used to analyze the dielectric recovery strength of the MCCB. A measuring system and an evaluation technique for the dielectric recovery strength of the MCCB are described. By using this system and method, the measurement to find out the dielectric recovery characteristics after current-zero for ready-made products is done and it is confirmed that which internal structure of the MCCB affects the dielectric recovery characteristics.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.309-312
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• 2003

In this study, the electrical characteristic of Symmetric high voltage MOSFET (SHVMOSFET) for display driver IC were investigated. Measurement data are taken over range of temperature (300K-400K) and various extended drain length. In high temperature condition(>400K), drain current decreased over 20％, and specific on-resistance increased over 30％ in comparison with room temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.909-911
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• 2002

Rises of current level at power applications, such as transformer, motor, power cable need for using stacked HTS tapes. In this paper, we measured rises of temperature and tap voltage in 4-stacked HTS tapes under over-current condition. We measured 4-stacked HTS tapes properties under over-current condition with a little temperature rise as well as a large temperature rise. Rises of temperature and tap voltage are measured by using E-type thermocouples and voltage taps, respectively. According to the results of measurement, rises of tap voltage under over-current condition with a large temperature rises depends on rises of temperature.

• 전기의세계
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• 제14권2호
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• pp.8-13
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• 1965

It is expected that the impurities contained in a solid state insulation material will affect a considerable influence on its break-down voltage, dielectric loss, and insulation resistance. In this thesis, as a preliminary experimental research for the investigation described above, the effect of metalic barrier between the electrodes on the creepin flash over discharge voltage along the surface of a solid insulation material has been investigated, and got some interesting results. It was found that generaly the flash over voltage rises when a metalic barrier is located between the electrodes. The results of this investigation will be taken into account as an important components on the insulation design to prevent the creeping flash over discharge in insulators, bushings, and so on.