• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.292-295
• /
• 2003

Conventional methods in time / frequency domain for evaluating the compensation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundamental reactive component and distorted component of nonlinear loads current. This method has excellent performance, but can not evaluate the characteristics of nonlinear load current whether it is inductive or capacitive. Therefore, To overcome problems mentioned previously, this paper deals with the simple Average power theory and the expanded 3-D current coordinates for evaluating the compensation performance of active power filters. To confirm the validity, active power filters simulator is developed using C-language. From the simulation, results are discuss their utility.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.8
• /
• pp.82-87
• /
• 2011

Induction motor is most widely used as the driving power in the industrial site. Induction motor current is composed of two parts, magnetizing current and load current. Load current uses energy what is doing the work. Load current varies with load variance but magnetizing current is constant, regardless of load variation. Magnetizing current needs for establishing the rotating magnetic field of induction motor and lags behind the voltage. Generally capacitor is used for power-factor compensation of inductive load. Self-excitation occurs when the capacitive reactive current from the capacitor is greater than the magnetizing current of the induction motor. When this occurs, excessive voltages can result on the terminals of the motor. This excessive voltage can cause insulation degradation and ultimately result in motor insulation failure. In this paper, we analyzed that how the magnetizing current and condenser current is operating at the allowable limit by the load variation. Condenser current is below allowable limit of magnetizing current but magnetizing current is above allowable limit at the lower load operation condition.

• Journal of Advanced Navigation Technology
• /
• v.27 no.1
• /
• pp.63-70
• /
• 2023

In this work, a capacitive wireless power transfer (C-WPT) system is presented for wireless sensor system (WSS) applications in marine propulsion shafts. For a single Q factor on both sides of the coupling capacitor and reactive power removal from the circuit, a double-sided LCLC converter and transformers topology are designed to drive the rotary C-WPT system for WSS on the shaft. Parallel-connected parallel plate rotating capacitors with a capacitance of 170 pF are designed and implemented for the C-WPT system on a snow rotating shaft. In the experimental results, the C-WPT system achieved a transmission efficiency of 66.67% with 7.8 W output power at 3 mm distance and 1 MHz operating frequency. Therefore, it was proved that the fabricated C-WPT system can supply power to the WSS of the rotating shaft.

• Proceedings of the KIEE Conference
• /
• 2005.10c
• /
• pp.26-28
• /
• 2005

Induction generator is the most common generator in wind energy systems because of its simplicity, ruggedness, little maintenance, price and etc. But the main drawbacks in induction generator is its need of reactive power means to build up the terminal voltage. This drawback is not an obstacle today where PWM inverters can accurately supplies the induction generator with its need from reactive power. For a insurance of three-phase induction generator requires capacitive reactance of the terminal. Most of previous work uses numerical iterative method to determine this minimum capacitor. But the numerical iteration takes long time and divergence may be occurs. In this paper is presented the design methods of the minimum self-excited capacitor required for induction generator operation. And a new formula from the equivalent circuit for stable generation operation of self-excited induction generator calculates the proper capacity to obtain the terminal voltage of the load stage. The validity of proposed design methods is confirmed by experimental and computed results.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2549-2552
• /
• 1999

The fictitious power theory in time domain is very easy to understand, but power analyzing time of active power is increased, because power is analyzed using signal techniques based on the correlation between voltage and current waveforms. Also, conventional methods in time/frequency domain to evaluate the compensation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundamental reactive component and distorted component of nonlinear loads current. This method has excellent performance, but can not evaluate the characteristics of nonlinear load current whether inductive or capacitive. Therefore, To overcome problems mentioned previously, this paper deals with the simple instantaneous power theory and the modified 3-D current coordinates for evaluating the compensation performance of active power filters. To confirm the validity, active power filters simulator is developed using C-language. From the simulation, results are discussed their utility.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.3
• /
• pp.64-72
• /
• 1999

The fictitious power theory in time domain is very easy to understand, but power analyzing speed of active power is increased, because power is analyzed using signal tedmiques based on the corre1ation between voltage and current wavefonns. Also, conventional methods in time/frequency domain to evaluate the correlation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundarrental reactive component and distorted component of nonlinear loads current. This trethod has excellent perfonnance, but can not evaluate the characteristics of nonlinear load current whether It is inductive or capacitive. Therefore, To overcorre problems trentioned previously, this paper deals with the simple average power theory and the modified 3-D current coordinates for evaluating the compensation perfonnance of active power filters. To confirm the validity, active power filter simulator is developed using C-language. From the simulation, results are discussed their utility.tility.

• Journal of Power Electronics
• /
• v.18 no.2
• /
• pp.627-639
• /
• 2018

The fact that the reliability of IGBTs has become a more and more significant aspect of power converters has resulted in an increase in the research on the open circuit (OC) fault location of IGBTs. When an OC fault occurs, a zero-current phenomena exists and frequently appears, which can be found in a lot of the existing literature. In fact, fault variables have a very high correlation with the zero-current interval. In some cases, zero-current interval actually decides the most significant fault feature. However, very few of the previous studies really explain or prove the zero-current phenomena of the fault current. In this paper, the zero-current phenomena is explained and verified through mathematical derivation, based on two-level and three-level NPC static var generators (SVGs). Mathematical models of single OC fault are deduced and it is concluded that a zero-current interval with a certain length follows the OC faults for both two-level and NPC three-level SVGs. Both inductive and capacitive reactive power situations are considered. The unbalanced load situation is discussed. In addition, simulation and experimental results are presented to verify the correctness of the theoretical analysis.

• Journal of the Korean Vacuum Society
• /
• v.22 no.2
• /
• pp.55-65
• /
• 2013

Sterilization of Neurospora crassa has been investigated in this research by using a surface air plasma with dielectric barrier discharged (DBD) structure under atmospheric pressure. The sinusoidal alternating current has been used in this experiment with discharge voltage of 1.4~2.3 kV. The phase difference between the voltage and current signals are found to be almost 80 degree due to the capacitive property of dielectric barrier. Temperature on the biomaterials has been minimized by radiating the heat with the air cooling system. It is noted that the substrate temperature remains under 37 degree for plasma exposure time of 10 minutes with operation of cooler system. It is found that the ozone, $O_3$, has been measured to be about 25~30 ppm within 1 cm region and to be about 5 ppm at the 150 cm downstream region away from the suface plasma. It is also noted that the nitric oxide, NO, and nitric dioxide, $NO_2$, are not nearly detected. Germination rate and mitochodrial activity of Neurospora crassa immersed in the deionized water have been found to be drastically decreased as the plasma treatment time and its electrical power are increased in this experiment. Here, the mitochondrial activity has been analyzed by MTT (3-(4,5-dimethy lthiazol-2yl)-2,5-diphenyl-2H-tetrazolium bromide) assay. However, sterilization of Neurospora crassa immersed in the Vogel's minimal media has been found to be low by plasma treatment, which is caused by surrounding background solution. This research shows the sterilization possibility of Neurospora crassa by using the noncontated surface DBD plasma, which is different from the plasma jet. This is mainly attibuted to the reactive species generated by the surface plasma, since they play a major role for inhibition of micobes such as Neurospora crassa.