The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jaehun Jung - One of the best experts on this subject based on the ideXlab platform.
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synthetic Test Circuit for thyristor valve in hvdc converter with new high current source
IEEE Transactions on Power Electronics, 2014Co-Authors: Yongho Chung, Seungtaek Baek, Jaehun JungAbstract:Synthetic Test Circuit (STC) for thyristor valve Test consists of a low-voltage high-current source to provide the forward current during turn-on state and a low-current high-voltage source to provide the reverse and forward voltage during turn-off state. This paper proposes a new low-voltage high-current source for STC that has a six-pulse thyristor converter and a two-phase chopper with an auxiliary switch. The operation of STC with a new low-voltage high-current source was verified through theoretical analysis and computer simulations with PSCAD/EMTDC. Based on computer simulation results, a scaled hardware system for the proposed Circuit was built and Tested to confirm the feasibility of implementing a real-size STC.
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a new synthetic Test Circuit for Testing thyristor valve in hvdc converter
The Transactions of the Korean Institute of Power Electronics, 2012Co-Authors: Jaehun Jung, Yongho Chung, Seungtaek BaekAbstract:This paper proposes a new synthetic Test Circuit (STC) to confirm the switching operation of thyristor valve in HVDC converter. The proposed STC uses a 6-pulse thyristor converter with 2-phase chopper as a high-current source to provide turn-on current to the Test valve. The operation of proposed STC was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware scaled model was built and Tested to confirm the feasibility of implementing a real-size Test facility. The proposed system has an advantage of simple structure and operation over the existing system.
Yongho Chung - One of the best experts on this subject based on the ideXlab platform.
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synthetic Test Circuit for thyristor valve in hvdc converter with new high current source
IEEE Transactions on Power Electronics, 2014Co-Authors: Yongho Chung, Seungtaek Baek, Jaehun JungAbstract:Synthetic Test Circuit (STC) for thyristor valve Test consists of a low-voltage high-current source to provide the forward current during turn-on state and a low-current high-voltage source to provide the reverse and forward voltage during turn-off state. This paper proposes a new low-voltage high-current source for STC that has a six-pulse thyristor converter and a two-phase chopper with an auxiliary switch. The operation of STC with a new low-voltage high-current source was verified through theoretical analysis and computer simulations with PSCAD/EMTDC. Based on computer simulation results, a scaled hardware system for the proposed Circuit was built and Tested to confirm the feasibility of implementing a real-size STC.
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new synthetic Test Circuit for thyristor valve in hvdc converter
IEEE Transactions on Power Delivery, 2012Co-Authors: Yongho ChungAbstract:This letter proposes a new synthetic Test Circuit (STC) to confirm the switching operation of the thyristor valve in the HVDC converter. The operation of the proposed STC was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware-scaled model was built and Tested to confirm the feasibility of implementing a real-size Test facility.
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a new synthetic Test Circuit for Testing thyristor valve in hvdc converter
The Transactions of the Korean Institute of Power Electronics, 2012Co-Authors: Jaehun Jung, Yongho Chung, Seungtaek BaekAbstract:This paper proposes a new synthetic Test Circuit (STC) to confirm the switching operation of thyristor valve in HVDC converter. The proposed STC uses a 6-pulse thyristor converter with 2-phase chopper as a high-current source to provide turn-on current to the Test valve. The operation of proposed STC was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware scaled model was built and Tested to confirm the feasibility of implementing a real-size Test facility. The proposed system has an advantage of simple structure and operation over the existing system.
Seungtaek Baek - One of the best experts on this subject based on the ideXlab platform.
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synthetic Test Circuit for thyristor valve in hvdc converter with new high current source
IEEE Transactions on Power Electronics, 2014Co-Authors: Yongho Chung, Seungtaek Baek, Jaehun JungAbstract:Synthetic Test Circuit (STC) for thyristor valve Test consists of a low-voltage high-current source to provide the forward current during turn-on state and a low-current high-voltage source to provide the reverse and forward voltage during turn-off state. This paper proposes a new low-voltage high-current source for STC that has a six-pulse thyristor converter and a two-phase chopper with an auxiliary switch. The operation of STC with a new low-voltage high-current source was verified through theoretical analysis and computer simulations with PSCAD/EMTDC. Based on computer simulation results, a scaled hardware system for the proposed Circuit was built and Tested to confirm the feasibility of implementing a real-size STC.
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a new synthetic Test Circuit for Testing thyristor valve in hvdc converter
The Transactions of the Korean Institute of Power Electronics, 2012Co-Authors: Jaehun Jung, Yongho Chung, Seungtaek BaekAbstract:This paper proposes a new synthetic Test Circuit (STC) to confirm the switching operation of thyristor valve in HVDC converter. The proposed STC uses a 6-pulse thyristor converter with 2-phase chopper as a high-current source to provide turn-on current to the Test valve. The operation of proposed STC was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware scaled model was built and Tested to confirm the feasibility of implementing a real-size Test facility. The proposed system has an advantage of simple structure and operation over the existing system.
Paulo F Butzen - One of the best experts on this subject based on the ideXlab platform.
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an array based Test Circuit for fully automated gate dielectric breakdown characterization
IEEE Transactions on Very Large Scale Integration Systems, 2011Co-Authors: John Keane, S Venkatraman, Paulo F ButzenAbstract:We propose an array-based Test Circuit for efficiently characterizing gate dielectric breakdown. Such a design is highly beneficial when studying this statistical process, where up to thousands of samples are needed to create an accurate time to breakdown Weibull distribution. The proposed Circuit also facilitates investigations of any spatial correlation of dielectric failures, and can monitor a progressive decrease in gate resistance. Measurement results are presented from a 32 × 32 Test array implemented in a 130-nm bulk CMOS process. Results show that this system is capable of taking accurate measurements across a range of voltages and temperatures, which is critical for extrapolating accelerated stress experiment results to expected device lifetimes under realistic operating conditions.
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an array based Test Circuit for fully automated gate dielectric breakdown characterization
Custom Integrated Circuits Conference, 2008Co-Authors: John Keane, S Venkatraman, Paulo F ButzenAbstract:We propose an array-based Test Circuit for efficiently characterizing gate dielectric breakdown. Such a design is highly beneficial when studying this statistical process, where up to thousands of samples are needed to create an accurate time to breakdown distribution. The proposed Circuit also facilitates investigations of any spatial correlation of dielectric failures, and can monitor a progressive decrease in gate resistance. Measurement results are presented from a 32 times 32 Test array implemented in a 130 nm process.
Bakker T.w. - One of the best experts on this subject based on the ideXlab platform.
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VibroCav: Hydrodynamic Vibration and Cavitation Technology
2012Co-Authors: Bakker T.w.Abstract:Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic vibrating-body-in-pipe tools as described in patents by Ivannikov are identified as having a major potential and being largely unexplored. Major advantages of these tools are simplicity of construction, scalability, powerful effects and attractive frequency range for well cleaning applications. Self induced vibration with a free body colliding with the pipe wall causes alternating flow around the body with a water hammer effect that enhances the vibration and cavitation. Cavitation can thus be generated at lower flow rates and at higher backpressures than with passive tools such as orifices. Cavitational collapse at high backpressure creates exceptionally strong effects, giving access to novel applications. At backpressures where even water hammer enhanced cavitation ceases to exist, very strong vibrations persist to pressure levels encountered in deep wells. This unique dual enhanced vibration and cavitation behaviour of the tools is the key to vibrating-body-in-pipe technology for which the new name VibroCav was coined. The study focuses on VibroCav tools with balls, except for one series of Tests with a so-called flip-flop body. Exploratory Tests in a 350 bar Test Circuit in Assen lead to the design of a 50 bar laboratory closed Test Circuit installed in the 3ME lab in Delft with facilities to apply up to 10 bar backpressure and up to 40 bar pressure differentials over the tools. In the 50 bar Test Circuit many experiments were carried out, firstly with bottom supported balls in a straight pipe and secondly with hanging balls in a pipe with a conical outlet allowing remote adjustment of the gap between the ball and the pipe wall. The influence of water composition, gas content and various ball materials was Tested. Selected high backpressure Test were carried out with a 350 bar closed Test Circuit in Drachten. A total of 29 field trials on an industrial scale were carried out for cleaning the porous media around water and oil wellbores under widely varying conditions and 5 field trials were done to evaluate the potential of the technology for the removal of scale deposits in wellbores. The laboratory experiments with the 50 bar Test Circuit delineated various operational modes of the VibroCav tools as function of flow rate and backpressure with regimes designated as (i) vibration only, (ii) active cavitation always combined with vibration, (iii) no vibration and passive cavitation and (iv) no vibration and no passive cavitation. The vibration regime persists to the maximum backpressure that could be reached and probably to much higher pressures, however at high flow rate conditions and a narrow gap vibration ceases when the Re value increases beyond the point of drag reduction due to shifting of the boundary separation point (Re approximately 3 x 105 for unbounded flow). Active cavitation is just as passive cavitation subdued by increasing backpressure; but in this Test Circuit it has still been observed at a backpressure of 63 barg. With a bottom supported tool as used in this Test Circuit a significant path downstream of the ball is obscured and active cavitation closer to the gap might still exist. This is the basis for the expectation that for this tool active cavitation may survive up to 100 barg backpressure. Tools with a hanging ball, in which cavitation is more clearly visible, were not Tested at such high backpressures. The influence of water quality and gas content proved to be insignificant. Lightweight balls showed in bottom supported tools violent vibration and strong active cavitation but were easily damaged by the high contact forces between the ball and the support. With hard steel balls and softer steel supports, bedding-in is observed due to contact forces beyond the elastic limit of the support. If the ball is softer than the support, the ball flattens, breaks or is otherwise damaged by the support. The field trials for cleaning porous media around wellbores combined with theoretical analysis provided valuable semi-quantitative understanding of the influence of frequency, source directivity, source energy, wellbore geometry and permeability damage on the penetration depth of sources for vibration based well cleaning. The most significant wave energy for cleaning porous media is provided by the slow Biot wave, which is a compressional wave in fluid in the interconnected pore network. The higher the virgin permeability of the rock and the lower the wave frequency the better is the penetration depth. Permeability deterioration due to pore fouling reduces the penetration depth of the cleaning treatment and with progressive fouling the pore damage may get out of reach of the cleaning tools. The limited number of scale removal trials showed significant potential of the VibroCav tools due to the combination of physical hammering, jetting, wave energy and shock waves of collapsing cavitation bubbles. The study provides a solid basis for a scientifically founded continuation of the development of VibroCav technology for many areas of application in several industrial sectors and should be regarded as the precursor for a range of innovating techniques
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VibroCav: Hydrodynamic Vibration and Cavitation Technology
2012Co-Authors: Bakker T.w.Abstract:Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic vibrating-body-in-pipe tools as described in patents by Ivannikov are identified as having a major potential and being largely unexplored. Major advantages of these tools are simplicity of construction, scalability, powerful effects and attractive frequency range for well cleaning applications. Self induced vibration with a free body colliding with the pipe wall causes alternating flow around the body with a water hammer effect that enhances the vibration and cavitation. Cavitation can thus be generated at lower flow rates and at higher backpressures than with passive tools such as orifices. Cavitational collapse at high backpressure creates exceptionally strong effects, giving access to novel applications. At backpressures where even water hammer enhanced cavitation ceases to exist, very strong vibrations persist to pressure levels encountered in deep wells. This unique dual enhanced vibration and cavitation behaviour of the tools is the key to vibrating-body-in-pipe technology for which the new name VibroCav was coined. The study focuses on VibroCav tools with balls, except for one series of Tests with a so-called flip-flop body. Exploratory Tests in a 350 bar Test Circuit in Assen lead to the design of a 50 bar laboratory closed Test Circuit installed in the 3ME lab in Delft with facilities to apply up to 10 bar backpressure and up to 40 bar pressure differentials over the tools. In the 50 bar Test Circuit many experiments were carried out, firstly with bottom supported balls in a straight pipe and secondly with hanging balls in a pipe with a conical outlet allowing remote adjustment of the gap between the ball and the pipe wall. The influence of water composition, gas content and various ball materials was Tested. Selected high backpressure Test were carried out with a 350 bar closed Test Circuit in Drachten. A total of 29 field trials on an industrial scale were carried out for cleaning the porous media around water and oil wellbores under widely varying conditions and 5 field trials were done to evaluate the potential of the technology for the removal of scale deposits in wellbores. The laboratory experiments with the 50 bar Test Circuit delineated various operational modes of the VibroCav tools as function of flow rate and backpressure with regimes designated as (i) vibration only, (ii) active cavitation always combined with vibration, (iii) no vibration and passive cavitation and (iv) no vibration and no passive cavitation. The vibration regime persists to the maximum backpressure that could be reached and probably to much higher pressures, however at high flow rate conditions and a narrow gap vibration ceases when the Re value increases beyond the point of drag reduction due to shifting of the boundary separation point (Re approximately 3 x 105 for unbounded flow). Active cavitation is just as passive cavitation subdued by increasing backpressure; but in this Test Circuit it has still been observed at a backpressure of 63 barg. With a bottom supported tool as used in this Test Circuit a significant path downstream of the ball is obscured and active cavitation closer to the gap might still exist. This is the basis for the expectation that for this tool active cavitation may survive up to 100 barg backpressure. Tools with a hanging ball, in which cavitation is more clearly visible, were not Tested at such high backpressures. The influence of water quality and gas content proved to be insignificant. Lightweight balls showed in bottom supported tools violent vibration and strong active cavitation but were easily damaged by the high contact forces between the ball and the support. With hard steel balls and softer steel supports, bedding-in is observed due to contact forces beyond the elastic limit of the support. If the ball is softer than the support, the ball flattens, breaks or is otherwise damaged by the support. The field trials for cleaning porous media around wellbores combined with theoretical analysis provided valuable semi-quantitative understanding of the influence of frequency, source directivity, source energy, wellbore geometry and permeability damage on the penetration depth of sources for vibration based well cleaning. The most significant wave energy for cleaning porous media is provided by the slow Biot wave, which is a compressional wave in fluid in the interconnected pore network. The higher the virgin permeability of the rock and the lower the wave frequency the better is the penetration depth. Permeability deterioration due to pore fouling reduces the penetration depth of the cleaning treatment and with progressive fouling the pore damage may get out of reach of the cleaning tools. The limited number of scale removal trials showed significant potential of the VibroCav tools due to the combination of physical hammering, jetting, wave energy and shock waves of collapsing cavitation bubbles. The study provides a solid basis for a scientifically founded continuation of the development of VibroCav technology for many areas of application in several industrial sectors and should be regarded as the precursor for a range of innovating techniques.3MEMechanical, Maritime and Materials Engineerin
