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A Study on Medium Voltage Power Supply with Enhanced Ignition Characteristics for Plasma Torch
Kyungsub Jung(정경섭),Yongsug Suh(서용석) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7
This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torch. Series resonant half-bridge topology is presented to be a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. The plasma torch rated for 3㎿, 2㎄ and having the physical size of 1m long is selected to be a high enthalpy source in waste disposal system. The steady-state and transient operations of plasma torch are simulated. The parameters of Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. Circuit simulation waveform shows that the ripple of arc current can be maintained within ±10% of its rated value under the existence of load disturbance. This power conversion configuration provides high enough ignition voltage around 5㎄ during ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.
Thyristor Rectifier for DC Arc Furnace with Enhanced Arc Stability
Kyungsub Jung(정경섭),Yongsug Suh(서용석),Taewon Kim(김태원),Taejun Park(박태준) 전력전자학회 2011 전력전자학술대회 논문집 Vol.2011 No.7
In this paper, the fundamental features of the arc stability DC arc furnace have been investigated, from the converter point of view. To compare of measurement arc data from DC arc furnace and the advanced arc simulations of magneto-hydrodynamics (MHD) and the well known Cassie-Mayr arc model have been extensively used. The MHD based arc simulation has been validated in the subcomponent level, for the free burning arc set up in the laboratory. The arc simulation predicted the arc voltage for different currents with the accuracy which satisfies engineering requirements. It has been shown that the arc current steepness at current zero determines the arc stability, and the associated peak arc resistance can be used as its quantitative measure. Based on the presented insight into the DC arc stability, a converter topology solution which realizes an optimal arc stability has been proposed. The main results presented in this paper provide a design guideline for the future DC arc furnace converter topology developments.
강태원(Taewon Kang),서용석(Yongsug Suh),박현철(Hyeoncheol Park),강병익(Byungik Kang),김성훈(Simon Kim) 전력전자학회 2013 전력전자학회 논문지 Vol.18 No.1
This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.