Yeong Chun Kim - Academia.edu (original) (raw)

Papers by Yeong Chun Kim

The support bearing requires high DN to raise specific energy efficiency for the state of the art... more The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(670 kgf) with high speed(about one million DNs) such as the pulsed generator, the selection of the bearing and lubrication method are very important. So the study for the critical speed of hollow rotor as well in accordance with high speed rotor and a full analysis are needed for rotor bearing system. This paper describes the analysis for rotor bearing system of pulsed generator compared with experimental data. The bearing and lubrication method are discussed as well with experimental data.

Biochemical and Biophysical Research Communications, 1999

... 69 (1998), pp. 392???413. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus... more ... 69 (1998), pp. 392???413. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (69). 25. G. Chen, M. Kamal, R. Hannon and TD Warner. Biochem. Pharmacol. 55 (1998), pp. 1621???1631. Article | PDF (760 K) | View Record in Scopus | Cited By in Scopus (30). 26. ...

IEEE Transactions on Applied Superconductivity, 2022

Experiments and finite-element analyses were conducted to investigate the characteristics of a 30... more Experiments and finite-element analyses were conducted to investigate the characteristics of a 300-turn smart insulation (SI) coil coated with vanadium trioxide (V2O3) placed in an external fluctuating magnetic field. The external fluctuating magnetic field generator was designed to allow sliding insertion through a fabricated non-rotating liquid-nitrogen tank inside the stator of a 1-MW superconducting rotating machine. The 300-turn SI coil was fabricated in a two-layer design with 150-turn windings in each layer. Experiments were conducted in such a manner that the SI coil did not rotate during the generation of the external fluctuating magnetic field owing to the rotating magnetic field of the stator. The SI coil with many turns showed no magnetic field delay because of the ramping time,thereby demonstrating controllability equivalent to that of a normal insulated coil. The stability of the SI coil was confirmed via repeated overcurrent tests, with and without an external fluctuating magnetic field.

IEEE Transactions on Applied Superconductivity, 2007

A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2... more A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2-dimensional (2D) magnetic field distribution considering several conditions such as superconducting wire length, machine efficiency, size and so on. By the way from 2D design it is not possible to consider the effect of end coils and end portions of stator iron yoke especially in superconducting machine with air-cored structure which increases magnetic field difference between 2D and 3D analysis. In this paper electrical design based on the 3D magnetic field distribution is conducted to get more proper design result and reduce design errors from 2D design approach. As the machine has larger capacity, the superconducting machine will show the advantages more and more over the conventional machine. Although the advantages at 1MW rating are not so great, the 3D design approach to get more optimized result would be very helpful for larger superconducting synchronous machine design. Through 3D analysis such as EMCN (equivalent magnetic circuit network) method and Flux-3D FEM (finite element method), we could get smaller machine size, higher efficiency, and smaller Bi-2223 HTS (high temperature superconducting) wire length than the 2D design result. Moreover influence of an important parameter, synchronous reactance, has been analysed on the machine performances such as voltage variation and output power.

IEEE Transactions on Applied Superconductivity, 2022

The KSFM Journal of Fluid Machinery, 2020

Journal of the Korean Society for Precision Engineering, 2020

JSME International Journal Series C, 2006

In recent years, a laminated rotor made of the insulated silicon steel laminates is increasingly ... more In recent years, a laminated rotor made of the insulated silicon steel laminates is increasingly adopted in the electrical machineries. While this laminated rotor offers good electrical performances, it is quite complicated to predict its stiffness as it is influenced by various factors such as material properties and shape of the laminates, characteristics of the insulation layer, lamination pressure and method of fitting. As it is difficult to model or define boundary conditions in the case of lamination pressure or fitting, the stiffness of the laminated rotor cannot simply calculated using conventional analytical method. Therefore, quantitative investigation on the influence of lamination pressure upon the stiffness of laminated rotor is highly required. In this study, natural frequency of the rotor is measured under various conditions of lamination pressure to investigate the influence of lamination pressure upon the stiffness of laminated rotor. It is found from the experiment that the natural frequency is increased with lamination pressure, and saturated near the 20% of the difference between the inner and outer diameters of the laminate. It is also found that the natural frequency can be controlled to 4-14% in the range of 1-10 MPa of lamination pressure. The saturated value of the stiffness of laminated rotor is expected to approach to that of shrinkage-fitted cylinder having the same inner and outer diameters under the same assembly condition. It is expected that the results would be helpful to design generators or motors using laminated rotors.

Journal of Sound and Vibration, 2006

Turbomachinery such as turbines, pumps and compressors, which are installed in transportation sys... more Turbomachinery such as turbines, pumps and compressors, which are installed in transportation systems, including aircraft, ships and space vehicles, etc., often perform their critical missions and are exposed to potential dangerous impact environments such as base-transferred shock forces. In this study a transient response analysis technique of a rotor system is proposed. The study involves applying the generalized finite element modeling method of a rotor-bearing system considering a base-transferred shock force along with the state-space Newmark method of a direct time integration scheme based on the average velocity concept. Experiments are performed to a test rig of a mock-up rotor-bearing system with a series of half-sine shock waves imposed by an electromagnetic shaker, and quantitative error analyses between analytical and experimental results are carried out. The results show that the transient responses of the rotor are sensitive to the duration times of the shocks. In particular, in cases where the frequencies, 1/(2 Â duration time), of the shock waves are close to the critical speed of the rotor-bearing system, resonances may occur and the transient responses of the rotor are consequently amplified. Overall, the analytical results agree quite well with the experimental data.

IEEE Transactions on Applied Superconductivity, 2012

There are a number of AC power devices using high temperature superconductor (HTS) such as Superc... more There are a number of AC power devices using high temperature superconductor (HTS) such as Superconducting Fault Current Limiter (SFCL), Superconducting Transformer, AC Superconducting cable and so on. However, the operating current of HTS power devices at alternating current (AC) circumstances is almost decided by critical current which is measured in direct current (DC) circumstances. Applying DC critical current criterion to AC power devices cannot be ideal. So, for AC power devices, a new AC critical current criterion must be needed. Commercial AC frequencies of current grid are 50 and 60 Hz. Therefore, in AC circumstance, the voltage induced by inductance is not negligible. For this paper, AC conducting experiments on variable superconducting tape samples were executed. The voltage induced by inductance is removed by filtering process and the voltage produced by resistance remains and is considered as a parameter (or guideline) of quench. With filtering process, amplitude of voltage generated by resistance can be calculated. As a result of those experiments, the 'Amplitude of input current'-'amplitude of voltage induced by resistance' curve was acquired and alternating critical current criteria were inferred.

Progress in Superconductivity and Cryogenics, 2010

 Abstract-- The superconducting synchronous motor or generator mostly has high permeability iron... more  Abstract-- The superconducting synchronous motor or generator mostly has high permeability iron only around outer yoke portion. Therefore, if excitation voltage (Back E.M.F) is calculated from 2 dimensional magnetic field distributions, it can be largely different from actual value due to additional voltage originated from end coils. In order to calculate the excitation voltage more accurately, 3 dimensional magnetic field calculation is necessary for including the end coil effect from large air-gap structure. The excitation voltage can be calculated by stator (armature) coil linkage flux originated from rotor (field) coil excitation, but it is difficult to calculate the flux linkage exactly because of complicated structure of the stator coil. This paper shows a method to calculate the excitation voltage from 3 dimensional magnetic energy that can be calculated directly from volume integration of magnetic flux density and field intensity scalar product through FEM (Finite Element ...

Journal of Electrical Engineering & Technology, 2018

:W@a *≤CU �k3a �k3a H˛�R �69v<�&/4n rotor( ), laminated rotor( ), stiffness( ), stiffness ... more :W@a *≤CU �k3a �k3a H˛�R �69v<�&/4n rotor( ), laminated rotor( ), stiffness( ), stiffness effect( ), natural frequency( ), 9ZH.3"&� E⁄4˙.r:Z U H‚:Z? &/8CGO critical speed( ), pulsed generator( ), rotordynamics( ) ABSTRACT The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(670 kgf) with high speed(about one million DNs) such as the pulsed generator, the selection of the bearing and lubrication method are very important. So the study for the critical speed of hollow rotor as well in accordance with high speed rotor and a full analysis are needed for rotor bearing system. This paper describes the analysis for rotor bearing system of pulsed generator compared with experimental data. The bearing and lubrication method are discussed as well with experimental data.

Journal of the Korean Society for Precision Engineering, 2020

IEEE Transactions on Applied Superconductivity, 2020

In this paper, we present biconditional binary decision diagrams (BBDDs), a novel canonical repre... more In this paper, we present biconditional binary decision diagrams (BBDDs), a novel canonical representation form for Boolean functions. BBDDs are binary decision diagrams where the branching condition, and its associated logic expansion, is biconditional on two variables. Empowered by reduction and ordering rules, BBDDs are remarkably compact and unique for a Boolean function. The interest of such representation form in modern electronic design automation (EDA) is twofold. On the one hand, BBDDs improve the efficiency of traditional EDA tasks based on decision diagrams, especially for arithmetic intensive designs. On the other hand, BBDDs represent the natural and native design abstraction for emerging technologies where the circuit primitive is a comparator, rather than a simple switch. We provide, in this paper, a solid ground for BBDDs by studying their underlying theory and manipulation properties. Thanks to an efficient BBDD software package implementation, we validate 1) speed-up in traditional decision diagrams applications with up to 4.4 gain with respect to other DDs, and 2) improved synthesis of circuits in emerging technologies, with about 32% shorter critical path than state-of-art synthesis techniques.

Progress in Superconductivity and Cryogenics, 2011

The support bearing requires high DN to raise specific energy efficiency for the state of the art... more The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(670 kgf) with high speed(about one million DNs) such as the pulsed generator, the selection of the bearing and lubrication method are very important. So the study for the critical speed of hollow rotor as well in accordance with high speed rotor and a full analysis are needed for rotor bearing system. This paper describes the analysis for rotor bearing system of pulsed generator compared with experimental data. The bearing and lubrication method are discussed as well with experimental data.

Biochemical and Biophysical Research Communications, 1999

... 69 (1998), pp. 392???413. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus... more ... 69 (1998), pp. 392???413. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (69). 25. G. Chen, M. Kamal, R. Hannon and TD Warner. Biochem. Pharmacol. 55 (1998), pp. 1621???1631. Article | PDF (760 K) | View Record in Scopus | Cited By in Scopus (30). 26. ...

IEEE Transactions on Applied Superconductivity, 2022

Experiments and finite-element analyses were conducted to investigate the characteristics of a 30... more Experiments and finite-element analyses were conducted to investigate the characteristics of a 300-turn smart insulation (SI) coil coated with vanadium trioxide (V2O3) placed in an external fluctuating magnetic field. The external fluctuating magnetic field generator was designed to allow sliding insertion through a fabricated non-rotating liquid-nitrogen tank inside the stator of a 1-MW superconducting rotating machine. The 300-turn SI coil was fabricated in a two-layer design with 150-turn windings in each layer. Experiments were conducted in such a manner that the SI coil did not rotate during the generation of the external fluctuating magnetic field owing to the rotating magnetic field of the stator. The SI coil with many turns showed no magnetic field delay because of the ramping time,thereby demonstrating controllability equivalent to that of a normal insulated coil. The stability of the SI coil was confirmed via repeated overcurrent tests, with and without an external fluctuating magnetic field.

IEEE Transactions on Applied Superconductivity, 2007

A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2... more A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2-dimensional (2D) magnetic field distribution considering several conditions such as superconducting wire length, machine efficiency, size and so on. By the way from 2D design it is not possible to consider the effect of end coils and end portions of stator iron yoke especially in superconducting machine with air-cored structure which increases magnetic field difference between 2D and 3D analysis. In this paper electrical design based on the 3D magnetic field distribution is conducted to get more proper design result and reduce design errors from 2D design approach. As the machine has larger capacity, the superconducting machine will show the advantages more and more over the conventional machine. Although the advantages at 1MW rating are not so great, the 3D design approach to get more optimized result would be very helpful for larger superconducting synchronous machine design. Through 3D analysis such as EMCN (equivalent magnetic circuit network) method and Flux-3D FEM (finite element method), we could get smaller machine size, higher efficiency, and smaller Bi-2223 HTS (high temperature superconducting) wire length than the 2D design result. Moreover influence of an important parameter, synchronous reactance, has been analysed on the machine performances such as voltage variation and output power.

IEEE Transactions on Applied Superconductivity, 2022

The KSFM Journal of Fluid Machinery, 2020

Journal of the Korean Society for Precision Engineering, 2020

JSME International Journal Series C, 2006

In recent years, a laminated rotor made of the insulated silicon steel laminates is increasingly ... more In recent years, a laminated rotor made of the insulated silicon steel laminates is increasingly adopted in the electrical machineries. While this laminated rotor offers good electrical performances, it is quite complicated to predict its stiffness as it is influenced by various factors such as material properties and shape of the laminates, characteristics of the insulation layer, lamination pressure and method of fitting. As it is difficult to model or define boundary conditions in the case of lamination pressure or fitting, the stiffness of the laminated rotor cannot simply calculated using conventional analytical method. Therefore, quantitative investigation on the influence of lamination pressure upon the stiffness of laminated rotor is highly required. In this study, natural frequency of the rotor is measured under various conditions of lamination pressure to investigate the influence of lamination pressure upon the stiffness of laminated rotor. It is found from the experiment that the natural frequency is increased with lamination pressure, and saturated near the 20% of the difference between the inner and outer diameters of the laminate. It is also found that the natural frequency can be controlled to 4-14% in the range of 1-10 MPa of lamination pressure. The saturated value of the stiffness of laminated rotor is expected to approach to that of shrinkage-fitted cylinder having the same inner and outer diameters under the same assembly condition. It is expected that the results would be helpful to design generators or motors using laminated rotors.

Journal of Sound and Vibration, 2006

Turbomachinery such as turbines, pumps and compressors, which are installed in transportation sys... more Turbomachinery such as turbines, pumps and compressors, which are installed in transportation systems, including aircraft, ships and space vehicles, etc., often perform their critical missions and are exposed to potential dangerous impact environments such as base-transferred shock forces. In this study a transient response analysis technique of a rotor system is proposed. The study involves applying the generalized finite element modeling method of a rotor-bearing system considering a base-transferred shock force along with the state-space Newmark method of a direct time integration scheme based on the average velocity concept. Experiments are performed to a test rig of a mock-up rotor-bearing system with a series of half-sine shock waves imposed by an electromagnetic shaker, and quantitative error analyses between analytical and experimental results are carried out. The results show that the transient responses of the rotor are sensitive to the duration times of the shocks. In particular, in cases where the frequencies, 1/(2 Â duration time), of the shock waves are close to the critical speed of the rotor-bearing system, resonances may occur and the transient responses of the rotor are consequently amplified. Overall, the analytical results agree quite well with the experimental data.

IEEE Transactions on Applied Superconductivity, 2012

There are a number of AC power devices using high temperature superconductor (HTS) such as Superc... more There are a number of AC power devices using high temperature superconductor (HTS) such as Superconducting Fault Current Limiter (SFCL), Superconducting Transformer, AC Superconducting cable and so on. However, the operating current of HTS power devices at alternating current (AC) circumstances is almost decided by critical current which is measured in direct current (DC) circumstances. Applying DC critical current criterion to AC power devices cannot be ideal. So, for AC power devices, a new AC critical current criterion must be needed. Commercial AC frequencies of current grid are 50 and 60 Hz. Therefore, in AC circumstance, the voltage induced by inductance is not negligible. For this paper, AC conducting experiments on variable superconducting tape samples were executed. The voltage induced by inductance is removed by filtering process and the voltage produced by resistance remains and is considered as a parameter (or guideline) of quench. With filtering process, amplitude of voltage generated by resistance can be calculated. As a result of those experiments, the 'Amplitude of input current'-'amplitude of voltage induced by resistance' curve was acquired and alternating critical current criteria were inferred.

Progress in Superconductivity and Cryogenics, 2010

 Abstract-- The superconducting synchronous motor or generator mostly has high permeability iron... more  Abstract-- The superconducting synchronous motor or generator mostly has high permeability iron only around outer yoke portion. Therefore, if excitation voltage (Back E.M.F) is calculated from 2 dimensional magnetic field distributions, it can be largely different from actual value due to additional voltage originated from end coils. In order to calculate the excitation voltage more accurately, 3 dimensional magnetic field calculation is necessary for including the end coil effect from large air-gap structure. The excitation voltage can be calculated by stator (armature) coil linkage flux originated from rotor (field) coil excitation, but it is difficult to calculate the flux linkage exactly because of complicated structure of the stator coil. This paper shows a method to calculate the excitation voltage from 3 dimensional magnetic energy that can be calculated directly from volume integration of magnetic flux density and field intensity scalar product through FEM (Finite Element ...

Journal of Electrical Engineering & Technology, 2018

:W@a *≤CU �k3a �k3a H˛�R �69v<�&/4n rotor( ), laminated rotor( ), stiffness( ), stiffness ... more :W@a *≤CU �k3a �k3a H˛�R �69v<�&/4n rotor( ), laminated rotor( ), stiffness( ), stiffness effect( ), natural frequency( ), 9ZH.3"&� E⁄4˙.r:Z U H‚:Z? &/8CGO critical speed( ), pulsed generator( ), rotordynamics( ) ABSTRACT The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(670 kgf) with high speed(about one million DNs) such as the pulsed generator, the selection of the bearing and lubrication method are very important. So the study for the critical speed of hollow rotor as well in accordance with high speed rotor and a full analysis are needed for rotor bearing system. This paper describes the analysis for rotor bearing system of pulsed generator compared with experimental data. The bearing and lubrication method are discussed as well with experimental data.

Journal of the Korean Society for Precision Engineering, 2020

IEEE Transactions on Applied Superconductivity, 2020

In this paper, we present biconditional binary decision diagrams (BBDDs), a novel canonical repre... more In this paper, we present biconditional binary decision diagrams (BBDDs), a novel canonical representation form for Boolean functions. BBDDs are binary decision diagrams where the branching condition, and its associated logic expansion, is biconditional on two variables. Empowered by reduction and ordering rules, BBDDs are remarkably compact and unique for a Boolean function. The interest of such representation form in modern electronic design automation (EDA) is twofold. On the one hand, BBDDs improve the efficiency of traditional EDA tasks based on decision diagrams, especially for arithmetic intensive designs. On the other hand, BBDDs represent the natural and native design abstraction for emerging technologies where the circuit primitive is a comparator, rather than a simple switch. We provide, in this paper, a solid ground for BBDDs by studying their underlying theory and manipulation properties. Thanks to an efficient BBDD software package implementation, we validate 1) speed-up in traditional decision diagrams applications with up to 4.4 gain with respect to other DDs, and 2) improved synthesis of circuits in emerging technologies, with about 32% shorter critical path than state-of-art synthesis techniques.

Progress in Superconductivity and Cryogenics, 2011