• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.9
• /
• pp.2280-2288
• /
• 2014

The conventional dimming control methods of LED (Light-emitting dioades) include Analog, PWM (Pulse Width Modulation), and FM (Frequency Modulation) Control. Analog dimming is controlled by adjusting forward current of Power LED. Although Analog dimming is possible to control linearly the brightness levels on a whole range (0%~100%), it comes into existence a variation of wavelength by changing the Power LED's forward current. PWM dimming has achieved by varying in duty of full current flowing to the Power LED. Generally, PWM dimming doesn't make variation of wavelength but have difficulty with adjusting the linear brightness level between 0% and 10%. FM dimming method is on the same wavelength as PWM dimming, however, it has problem of flickering at low level of dimming. This paper propose a efficient dimming control method of Power LED in order to overcome the disadvantages of the above mentioned methods. We apply to Analog method in low level of dimming control and use PWM method in dimming range from 10% to 100%. For the experiment, we design and implement a circuit and test the proposed method. Consequently, we can control the linear brightness of Power LED across the whole range and get the constant wave at different dimming level. The experimental results show the benefits of the proposed method.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.848-850
• /
• 2002

Single phase induction motor is directly used usual source, it can be a source of an appliance such as mechanical fan, refrigerator, washing machine, etc. Especially capacitor-run single phase induction motor is suitable to make more inexpensive and high efficient products because it is more high efficiency, and good to start than other single phase induction motors. Generally, voltage and current of capacitor-run single phase induction motor transfer to the part of positive phase and negative phase based on two motor theory. In this paper, we simulate the torque characteristics to capacitance variation from single phase induction motor's equivalent circuit. Through the test using the real motor, we compare and investigate the maximum torque of run state related with capacitance and the adequacy of the converted model.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.1241-1243
• /
• 2002

This study presents a AC electric railway system analysis using PSCAD/EMTDC for circuit analysis and fault studies. This PSCAD/EMTDC model includes feeder, contact line, rails. Scott-transformer. Auto-transformer and so on. This model is based on four-port network which is an extension of two-port network theory. In order to verify the proposed model, fault studies of a test system are performed.

• Proceedings of the KIEE Conference
• /
• 1990.11a
• /
• pp.336-339
• /
• 1990

The permanent magnet synchronous motor windings are energized by sinusoidal excitation current. The frequency of the winding excitation current is synchronous with motor movement and the phase is a function of the motor position with respect to the stator. The total operational speed range of the system is substantially incresed by controlling the phase of the excitation currents at a function of the desired speed. This becomes the torque angle between stator rotating field and motor position. In this paper, torque angle control method is described for surface permanent magnet synchronous motor (SPMSM). The control circuit for realizing control method is investigated and the system test is carried out.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.7
• /
• pp.572-575
• /
• 2009

In this study, we proposed WLED(White-Light Emitting Diode) driver IC for mobile applications. This IC drove WLED for mobile applications with low input voltage and high efficiency by using boost converter. The device was designed by using boost converter applied current-mode control algorithm and provided PWM(Pulse Width Modulation) & analog dimming. Designed IC consisted of bias block, drive block, control block, protection block. We confirmed this device worked well through a application PCB (Printed Circuit Board) test.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.12
• /
• pp.171-176
• /
• 2010

This paper presents the electric field for 22.9[kV]/380[V], 2[MVA] mold transformer are analysed using FEM(finite element method). The electric field was calculated for the voltage applied to the transformer. Then, it is analysed that the maximum electric field occurred between high voltage turns. Capacitance is calculated with energy method. Surge impulse test simulation is studied by modeling circuit with capacitance and inductance. This paper obtain the result that is about influence of electric field in distribution mold transformer adopted.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.2
• /
• pp.465-470
• /
• 1999

This paper presents a design method of driving system for EV(Electric Vehicle). EV driving system consist of batteries, battery interface system and inverter. The power control circuit of the driving system is simple, since only one PWM(Pulse Width Modulation) inverter is used. These test spectrums and waveforms can be used to determine the filter component ratings as well as to compute the harmonics injected into the source. The hybrid control strategy which can reduced harmonic components. The analysis results indicate that the required capacity of the condenser can be reduced with LC filter. In this paper, the design and implementation of the proposed systems are described and some experimental results are given to show the performance of this driving system. The control strategy of the system to available inverter's power and motor's power and torque is discussed.

• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.107-109
• /
• 2003

Single phase induction motor is directly used usual source, it can be a source of an appliance such as mechanical fan, refrigerator, washing machine, etc. Especially capacitor-run single phase induction motor is suitable to make more inexpensive and high efficient products because it is more high efficiency, and good to start than other single phase induction motors. Generally, voltage and current of capacitor-run single phase induction motor transfer to the part of positive phase and negative phase based on two motor theory. In this paper, we simulate the torque characteristics to capacitance variation from single phase induction motor's equivalent circuit. Through the test using the real motor, we compare and investigate the maximum torque of run state related with capacitance and the adequacy of the converted model.

• Journal of Power Electronics
• /
• v.18 no.5
• /
• pp.1513-1522
• /
• 2018

This paper proposes a new islanding detection method for inverter-based distributed generators by continuously injecting a negligible amount of 2nd order harmonic current. The proposed method adopts a proportional resonant (PR) controller for the output current control of the inverter, and a PR filter to extract the 2nd order harmonic voltage at the point of common coupling (PCC). The islanding state can be detected by measuring the magnitude ratio of the 2nd order harmonic voltage to the fundamental voltage at the PCC by injecting a 2nd order harmonic current with a 0.8% magnitude. The proposed method provides accurate and fast detection under grid voltage unbalance and load unbalance. The operation of the proposed method has been verified through simulations and experiments with a 5kW hardware set-up, considering the islanding test circuit suggested in UL1741.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.822_823
• /
• 2009

Superconducting fault current limiters (SFCLs) provide one of the most effective solutions to cope with enormous increase of fault current level. The 13.2 kV/ 630 A class resistive SFCL using coated conductor (CC) was developed and its short-circuit test was successful. Successful commercialization of the SFCL requires that no loss is produced by impedance of limiting coil during normal operation. Since the limiting coil consists of inner layer and outer layer, gap length between the layers is an important parameter to analyze the electromagnetic characteristics of coil. This paper deals with the electromagnetic characteristics of coil according to gap length through the simulation and analysis in comparison with experiment results.