• Korean Journal of Mathematics
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• v.19 no.1
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• pp.53-59
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• 2011

We study some properties of integrable semigroup and its generator, and then we establish convergence of integrable semigroups on the norming dual pairs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.3
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• pp.428-438
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• 2016

This paper shows the design of the 100 kW IPMSG for small hydraulic power generator. The high-efficient generator, method of the dual layer interior permanent magnet was studied to improve the method of the single layer interior permanent magnet, which is mostly used. Analysis of magnet arrangement and cogging torque was done by FEM. According to structure analysis of dual layer interior permanent magnet, the amount of usage of the permanent magnet was reduced and cogging torque was decreased as well. With these successful results, the high-efficient generator design was accomplished. Based on the results of the structure analysis, the test product was designed and manufactured. And the design values and performance outputs were compared and verified with success. Also, the economic feasibility was conducted based on the electric power generated from the test product installed at the site. By the B/C analysis, in case that only SMP was analyzed, B/C ratio was 1.24 at the discount ratio of 5.5%, which considered to be economically feasible. The study is expected to be used for the application of developing large scale high-efficient interior permanent magnet synchronous generator.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.1
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• pp.25-34
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• 2017

The concentric dual-buoy Wave Energy Converter (WEC), which consists of external buoy (hallow-cylinder) with toroidal appendage and cylindrical internal buoy within the moon-pool is suggested in this research and its performance in various wave conditions is studied. The Linear Electric Generator (LEG), consisting of a permanent magnet and coils, is used as a direct Power Take-Off (PTO) system. To maximize the electrical energy extracted from the PTO system, the relative heave motions between the dual buoys must be highly amplified by the multiple resonance phenomena of dual-buoy and internal-fluid motions. The high-performance range can be widened by distributing those natural frequencies with respect to the peak frequency of the wave spectrum. The performance of the newly developed dual-buoy WEC was measured throughout the systematic 1:5.95-model test in regular and irregular waves conducted in a wave tank at Seoul National University. The model-test results are also validated by an independently developed numerical method.

• Journal of Power Electronics
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• v.12 no.6
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• pp.886-894
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• 2012

This paper presents a secondary-side, dual-mode feedback LLC resonant controller IC with dynamic PWM dimming for LED backlight units. In order to reduce the cost, master and slave outputs can be generated simultaneously with a single LLC resonant core based on dual-mode feedback topologies. Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) schemes are used for the master stage and slave stage, respectively. In order to guarantee the correct dual feedback operation, Phased-Locked Loop (PLL)-based automatic duty control circuit is proposed in this paper. The chip is fabricated using $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology, and the die size is $2.5mm{\times}2.5mm$. The frequency of the gate driver (GDA/GDB) in the clock generator ranges from 50 to 425 kHz. The current consumption of the LLC resonant controller IC is 40 mA for a 100 kHz operation frequency using a 15 V supply. The duty ratio of the slave stage can be controlled from 40% to 60% independent of the frequency of the master stage.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.72-81
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• 2011

In order to understand the operation characteristics and major design parameters of a dual combustion ramjet engine, a fundamental analysis model based on gasdynamics and thermodynamic theories was established. The preliminary performance analysis was accomplished and the results clearly describe the intimate relationship between air inlets, gas generator, and supersonic combustor. The methodology presented provides a means for quantitatively determining the geometries of the gas generator and supersonic combustor and assessing the effects on performance of each of the engine components. Also the design results for a basic configuration were provided.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.318-325
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• 2011

In order to understand the operation characteristics and major design parameters of a dual combustion ramjet engine, a fundamental analysis model based on gasdynamics and thermodynamic theories was established. The preliminary performance analysis was accomplished and the results clearly describe the intimate relationship between air inlets, gas generator, and supersonic combustor. The methodology presented provides a means for quantitatively determining the geometries of the gas generator and supersonic combustor and assessing the effects on performance of each of the engine components. Also the design results for a basic configuration were provided.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.64-70
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• 2010

High capacity UPS and emergency generators are commonly employed at facilities where power interruption is not allowed. Nowadays, combinations of existing commercial incoming power and an emergency generator or combination of multiple generators and CTTS(Closed Transition Transfer Switch) is adopted sometimes for more reliable power supply. In this paper, application of CTTS and STS(Static Transfer Switch) to dual-power line is suggested for highly reliable uninterruptible power. By realizing such a system, construction of incoming power facilities, installation of emergency generator and large capacity UPS can be omitted, through which saving of the installation space and corresponding capital investment can be expected.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.163-167
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• 2007

Silver is widely used for catalytic decomposition of hydrogen peroxide, but start-up at room temperature is difficult and cannot withstand at high temperature. In this paper, to overcome these short-comings, a dual catalytic bed which consists of a vaporizer catalyst and a high temperature catalyst was studied. Platinum was selected as the vaporizer catalyst and perovskite type catalyst was selected for the high temperature catalyst. Preliminary test demonstrated start-up capability with non-preheating at room temperature and good thermal stability at high temperature.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.295-300
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• 2001

A variety of high voltage DC power supplies employing the high frequency inverter are difficult to achieve soft switching considering a quick response and no overshoot response under the wide load variation ranges which are used in medical-use x-ray high voltage generator from 20kV to 150kV in the output voltage and from 0.5mA to 1250mA, respectively. The authors develops soft switching high voltage DC power supply designed for x-ray power generator applications, which uses series resonant inverter circuit topology with a multistage voltage multiplier instead of a conventional high voltage diode rectifier connected to the second-side of a high-voltage transformer with a large turn ratio. A constant on-time dual mode frequency control scheme operating under a principle of zero-current soft switching commutation is described. Introducing the multistage voltage multiplier, the secondary transformer turn-numbers and stray capacitance of high-voltage transformer is effective to be greatly reduced. It is proved that the proposed high-voltage converter topology with dual mode frequency modulation mode control scheme is able to be the transient response and steady-state performance in high-voltage x-ray tube load. The effectiveness of this high voltage converter is evaluated and discussed on the basis of simulation analysis and observed data in experiment.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1455-1468
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• 2016

This paper presents a grid-connected dual stator-winding induction generator (DWIG) wind power system suitable for wide wind speed ranges. The parallel connection via a unidirectional diode between dc buses of both stator-winding sides is employed in this DWIG system, which can output a high dc voltage over wide wind speed ranges. Grid-connected inverters (GCIs) do not require booster converters; hence, the efficiency of wind energy utilization increases, and the hardware topology and control strategy of GCIs are simplified. In view of the particularities of the parallel topology and the adopted generator control strategy, we propose a novel excitation-capacitor optimization solution to reduce the volume and weight of the static excitation controller. When this excitation-capacitor optimization is carried out, the maximum power tracking problem is also considered. All the problems are resolved with the combined control of the DWIG and GCI. Experimental results on the platform of a 37 kW/600 V prototype show that the proposed DWIG wind power system can output a constant dc voltage over wide rotor speed ranges for grid-connected operations and that the proposed excitation optimization scheme is effective.