• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.13-14
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• 2011

The power conversion converter for driving the wireless power transfer system is can be into the two part of the DC power conversion rectifier and the high frequency dc-ac power conversion inverter. In this paper, The operating characteristics of the Class-${\Phi}_2$ resonant inverter have been investigated through by simulation and by experiment. It can be switched at a high frequency without the switching losses and the harmonics are reduced effectively due to the input LC filter. Its switching frequency is 1MHz and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output peak voltage is 170V. The resonant inverter module operated at the commercial power source of 220V was built. And also the electromagnetic coupled resonance coils were designed for wireless power transfer with a 1MHz operating frequency. As a experimental result, the wireless power transmission was confirmed and it is varified the validity of the experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.590-595
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• 2004

The shape and size variations of the nanopatterns produced on a positive photoresist using a near-field scanning optical microscope(NSOM) are investigated with respect to the process variables. A cantilever type nanoprobe having a 100nm aperture at the apex of the pyramidal tip is used with the NSOM and a He-Cd laser at a wavelength of 442nm as the illumination source. Patterning characteristics are examined for different laser beam power at the entrance side of the aperture( $P_{in}$ ), scan speed of the piezo stage(V), repeated scanning over the same pattern, and operation modes of the NSOM(DC and AC modes). The pattern size remained almost the same for equal linear energy density. Pattern size decreased for lower laser beam power and greater scan speed, leading to a minimum pattern width of around 50nm at $P_{in}$ =1.2$\mu$W and V=12$\mu$m/. Direct writing of an arbitrary pattern with a line width of about 150nm was demonstrated to verify the feasibility of this technique for nanomask fabrication. Application on high-density data storage using azopolymer is discussed at the end.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.2
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• pp.70-75
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• 2014

A track circuit is a critical piece of equipment that allows the existence of the trains on the track to be detected. Train detection is very important for the signal safety equipment. It allows for the confirmation of a train's location, the locking of switch points, the coordination of safe distance between trains, and the advance notice of a train's arrival. Track circuits can be powered by AC or DC. The DC track circuits are usually used on non-electrified tracks. On these tracks, many signal errors can be caused by lightning or problems with the power source. These problems can also cause damages to the rectifiers which must be repaired or replaced, promptly. This issue is especially problematic in the summer because of the higher frequency of thunderstorms. Issues with track circuits also cause problems for other equipment, such as railroad crossings and switch points. This further disrupts the safe operation of trains. This study aims to enhance maintenance efficiency and improve safety by utilizing parallel operation and multiplexing of a DC track circuit as well as installing an external surge protector. The experimental results on the operation of the proposed method is also presented.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.473-478
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• 2005

In home appliances, electric energy is optimally controlled by using power electronics technology, creating a comfortable environment in terms of energy saving, low sound generation, and reduced time consumption. Usually simplicity and robustness make the three phase induction motor attractive for use in domestic appliance, including washing machines. Two main fpes of domestic washing machine have evolved. We focus on the front loading machine favored in Europe, which has a horizontal drum axis. With the advent of electronic control, universal motor, with a phase controller operating directly from the ac source, has become popular in washing machine. The efficiency improvement in home appliances is very important for customers. Induction motor efficiency can be improved by means of loss reduction, which can be realized by motor selection and design, improvement of the waveforms supplied by power inverter, utilizing a suitable control method. So this paper describes the architecture and feature of washing machine fed induction motor drive under minimizing losses vector control.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.314-315
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• 2011

This paper introduces the design and control method of braking chopper circuit which can supply input power to ventilation inverter of traction control system. The DC input voltage from auxiliary block (static inverter) is normally used as an input of ventilation inverter. It converts DC input to AC output voltage to drive cooling fans for traction control system and traction motors. The electrical braking force is very important for high speed train to guarantee safety even though the train is running in the dead section where the pantograph voltage is not supplied. When the high speed train decelerate speed in dead section, the regenerative energy is dissipated by braking resistor. This paper proposed the braking chopper control method to implement rheostatic braking function and the appropriate chopper circuit for supplying voltage source to ventilation inverter during rheostatic braking mode. The proposed chopper circuit makes it possible for traction control system to regenerate power continuously regardless of the existence of pantograph voltage. The feasibility of proposed braking chopper control and circuit were proven by inertia load test and actual train field test.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1064_1065
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• 2009

PV (Photovoltaic) power generation system has been widely studied as a clean and renewable power source. Tracking the MPP (maximum power point) of a PV array is usually an essential part of a PV system. This paper describes POS (Photovoltaic Output Sensorless) MPPT method and optimization technique of its operational characteristics for grid-connected PV generation system. A DC-DC converter has been used to step-up the PV voltage and DC-AC converter has been used for connecting the system to the grid. Optimization technique has been implemented to optimize the current and voltage controller gain parameters and duty ratio increment of DC-DC converter. Simulation results reveal that the proposed control has better response.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1948_1949
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• 2009

All the power generating station require dc auxiliary power systems to operate those dc components that must be available if a loss of ac power occur. Some examples of such components are auxiliary motors, circuit breakers, relays and solenoids. The dc source may be one common battery for both power and control or two separate batteries; one for power and another for control. Typically, a dc auxiliary power system is designed as an ungrounded system, instead of grounded system, so that a low-resistance ground fault on one of its two polarities will not affect the operation of the system, thus increasing system reliability and continuity of service. A ground detector should provide a high polarity-to-ground resistance so that a single ground fault occurring on the system will not affect the operation of that system. Sensitive relays have been known to energize momentarily while the cable and capacitive charge to ground shifts[1]. A power station had experienced this kind of incident and performed root cause analysis based on PC based simulation program known as PSpice. This simulation showed adapted relays on the system energize momentarily and design criteria on this relay should be corrected.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1796-1801
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• 2008

In this paper, a new current based maximum power point tracking (CMPPT) method is proposed for a single phase photovoltaic power conditioning system and the current based MPPT modifies incremental conductance method. The current based MPPT method makes the entire control structure of the power conditioning system simple and uses an inherent current source characteristic of solar cell array. In addition, digital phase locked loop using an all pass filter is introduced to detect phase of grid voltage as well as peak voltage. Controllers about dc/dc boost converter, dc-link voltage, dc/ac inverter is designed for a coordinated operation. Furthermore, PI current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. 3kW prototype photovoltaic power conditioning system is built and its experimental results are given to verify the effectiveness of the proposed control schemes.

• Journal of Nutrition and Health
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• v.27 no.9
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• pp.930-939
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• 1994

Vitamin B-6 nutrition has been shown to be inadequate in many population groups including pregnant and lactating women, and in infants. Vitamin B-6 intake was measured in 98 pregnant mothers and a total of 172 cord blood samples of their and other new born infants were analyzed for erythrocyte alanine aminotransferase(EALAT) activities with or without the addition of pyridoxal-5-phosphate to assess vitamin B-6 status of the infants. The average daily vitamin B-6 intake of the pregnant mothers was 1.79mg$\pm$0.88(81.4% of the Recommended Dietary Allowances ; RDA) and vitamin B-6 to protein intake ration was 0.017mg vitamin B-6/g protein. Thirty-eight percent of the pregnant women consumed diets which provided less than the RDA for vitamin B-6 during pregnancy. Seventy-two percent of the dietary pyridoxine intake was provided by the plant food source whose bioavailability was reported to be lower when compared to that of the animal food. The average activity coefficient(AC) values of the cord blood EALAT was 1.41$\pm$0.11, and 32% of the blood samples had EALATAC values greater than 1.25, suggesting that vitamin B-6 status of the newborns might be less than adequate.

• Journal of Power Electronics
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• v.9 no.3
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• pp.343-353
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• 2009

In this paper, a nonlinear controller is proposed for Doubly-Fed Induction Machine (DFIM) drives. The nonlinear controller is designed based on an adaptive backstepping control technique, using a fifth order model of an induction machine in the synchronous d & q axis rotating reference frame, whose d axis coincides with the space voltage vector of the main AC supply, and using the rotor current and stator flux components as state variables. The nonlinear controller can perfectly track the torque reference signal measured in the stator terminals under the condition of unity power factor regulation, in spite of the stator and rotor resistance variations. In order to make the drive system capable of operating in the motoring and generating modes below and above the synchronous speed, two level Space-Vector PWM (SV-PWM) back-to-back voltage source inverters are employed in the rotor circuit. It is confirmed through computer simulation results that the proposed control approach is effective and valid.