• Journal of Power Electronics
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• v.15 no.3
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• pp.610-620
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• 2015

An inherent zero-voltage and zero-current-switching phase-shifted full-bridge converter with reverse-blocking insulated-gate bipolar transistor (IGBT) or non-punch-through IGBT is proposed in this paper. This converter not only ensures that the switches in the lagging leg works at zero-current switching, but also minimizes circulating conduction loss without any additional auxiliary circuits. A 1.2 kW hardware prototype is designed, fabricated, and tested to verify the proposed topology. The control loop design procedures with small-signal models are also presented. A simple, low-cost, and robust democratic current-sharing circuit is also introduced and verified in this study. The proposed converter is a suitable alternative for compact, cost-effective applications with high-voltage input.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1628-1632
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• 2013

HEP(Head Electric Power) system, supplying 3-phase service power to the coach vehicles, is a kind of special auxiliary power equipment which is boarded on 8200 series electric locomotives in KORAIL. This equipment shares high voltage DC link with a main propulsion converter/inverter systems. It was difficult to use high frequency PWM technique so that GTO has been used as a power device same like the main power system. Due to low PWM frequency(300Hz) of HEP inverter, the output voltage has less power quality comparing to normal SIV(Static Inverter) system. In this paper, an optimal PWM strategy is presented for new IGBT type HEP inverter system. Several PWM techniques were investigated to improve output voltage quality under fixed lower filter inductance and not high PWM frequency. Finally PC simulations have been done to clarify its availability.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1667-1668
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• 2008

There are three main devices such as boiler producing steam, turbine driving generator and generator producing electricity. An electrical generator in power plant is driven and maintained its speed at rated by steam turbine which is coupled into generator directly. Turbine auxiliary devices such as condenser, deaerator, feed water heater, gland steam condenser, pump recirculation equipment, feed water pump, and so on should be operated well so that the steam turbine exert its maximum efficiency. There are many control loop such as hot well level and condenser recirculation, deaerator level, pegging steam pressure, feed water heater level, feed water pump recirculation. In this paper condenser level control and deaerator level control are going to be described.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.19-25
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• 1997

This paper presents the short-term operation scheduling on cogeneration system connected with auxiliary equipment by using the possibility fuzzy theory. The possibility fuzzy theory is a method to obtain the possibility boundary of the solution from the fuzzification of coefficients. Simulation is carried out to obtain the boundary of heat production in each time interval. Simulation results show the flexible operation boundary to establish effectively operation scheduling.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2008-2011
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• 1998

When the vector control, which does not need a speed signal from a mechanical speed sensor, it is possible to reduce the cost of the control equipment and to improve the control performance in many industrial application. This paper describes a rotor speed identification method of induction motor based on the theory of Model Reference Adaptive System(MRAS). The identifier execute the rotor speed identification so that the vector control of the induc-tion motor may be achieved. The improved auxiliary variable are introduce to perform accurate rotor speed identification. Simulation and experimental result show the validity of the proposed control method.

• Journal of Drive and Control
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• v.10 no.2
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• pp.1-6
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• 2013

This study describes a method which can attenuate reaction force effectively for an air spring system composed of an air spring and auxiliary chamber. For the analysis, the nonlinear governing equation of the air spring system is derived. For a performance improvement of the system, change of the heat transfer effect and the mass flow rates is included in the analysis of the air spring system. The simulation study is presented to show the reaction force is changed by variations in heat transfer characteristics and the air spring system of isothermal process has the best performance. As a result, to improve attenuation characteristics of reaction force, a process in the air spring system should be maintained near isothermal process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.336-342
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• 2018

Noise reduction is an important issue in auxiliary power unit(APU) of tracking equipments for using military. In this study, we designed and tested reduction methods of structure borne noise and airborne source noise at the auxiliary power unit. From the bench test results, it is found that the effect of noise reduction is about 22 dB(A) if the silencer is redesigned, which is the rescue structure. However, the influence of noise reduction by air is insufficient. In addition, it is confirmed that the effect of noise reduction is excellent when structure borne noise reduction is applied to the vehicle. We expected that the test results of this study are used as basic data to reduce the noise of other tracking equipment developed later.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.1-11
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• 2017

Most of the local limestone mines are developed as large-opening underground mines, while mine ventilation is heavily dependent on the natural ventilation and auxiliary systems, rather than the mechanical ventilation system using main fans. The current auxiliary ventilation system with fan and ducting requires optimization since enhanced deployment of diesel equipment demands higher airflow rate and the associated cost is expected to be too excessive for the local mine operators. This paper aims at optimizing the fan capacity for the working site ventilation through comparing the fan pressure in the mine airway and the ventilation efficiency of an axial-flow fan and a propeller fan developed in this study.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1480-1488
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• 2015

In this paper, a revolutionary buck converter is proposed with soft-switching technology, which is realized by a coupled inductor. Both zero-voltage switching (ZVS) of main switch and zero-current switching (ZCS) of freewheeling diode are achieved at turn on and turn off without using any auxiliary circuits by the resonance between the parasitic capacitor and the coupled inductor. Furthermore, the peak voltages of the main switch and the peak current of the freewheeling diode are significantly reduced by the coupled inductor. As a result, the proposed converter has the advantages of simple circuit, convenient control, low consumption and so on. The detailed operation principles and steady-state analysis of the proposed ZVS-ZCS buck converter are presented, and detailed power loss analysis and some simulation results are also included. Finally, experimental results based on a 200-W prototype are provided to verify the theory and design of the proposed converter.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.119-131
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• 2014

For quick and accurate ground investigation in wide construction site being not easy to access, advanced dynamic cone penetration test equipment was developed based on widely used equipment abroad. Advantages of existing equipment of portability and simple testing method were reflected in the new developed equipment. Meanwhile, by extending connection of lower rod, penetration depth is raised to 6m from 1 m of the existing equipment. Moreover, by assembly of hammer (2+3+3kg) and cone (3 types) etc., it is possible to perform test under the same conditions with those by German and Japan dynamic cone penetration test equipment (Tsukuba, PWRI and SH types). Auxiliary equipment was applied to make sure of perpendicularity as penetration depth increases. Applicability of the new developed equipment was evaluated through tests on various fields and its reliability was verified.