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Chris W. Bumby - One of the best experts on this subject based on the ideXlab platform.
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Numerical Modelling of Dynamic Resistance in a Parallel-Connected Stack of HTS Coated-Conductor Tapes
IEEE Transactions on Applied Superconductivity, 2020Co-Authors: Justin M. Brooks, Zhenan Jiang, Rodney A. Badcock, Mark D. Ainslie, Stuart C. Wimbush, Chris W. BumbyAbstract:Dynamic Resistance is observed in type-II superconductors carrying a DC transport current while simultaneously exposed to an alternating magnetic field. The appearance of a nonzero Resistance is attributed to the interaction between the transport current and moving fluxons. This effect is relevant to many superconductor applications such as high-temperature-superconductor (HTS) flux pumps, DC/AC magnets, synchronous machines, and persistent current switches. Here, we present a finite element method (FEM) analysis of both the time averaged Dynamic Resistance and the instantaneous current sharing behaviour in a cable comprised of a stack of four YBCO thin films connected in parallel. Numerical modelling was performed using the H-formulation method implemented in the commercial software COMSOL. The model employs experimentally measured values of the angular dependence of the critical current I.(B, 8) and the flux creep exponent n(B, 8). A single threshold field is observed, above which a finite Dynamic Resistance is observed in all tapes simultaneously. The time-averaged Dynamic Resistance of individual tapes tends to be larger for the exterior tapes than the interior tapes, but this difference decreases as the total transport current in the cable increases. We attribute this to shielding currents flowing in the exterior tapes during the majority of the cycle, which displace net DC current into the interior tapes. However, the relative proportion of DC transport current flowing in the exterior and interior tapes is also observed to vary periodically once per half cycle of the applied field. This is due to the periodic trapping of return screening currents in the interior tapes.
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Dynamic Resistance measurement in a YBCO wire under perpendicular magnetic field at various operating temperatures
Journal of Applied Physics, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Gennady Sidorov, Jin FangAbstract:Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear Mikitik and Brandt equation for i ≤ 0.2 and with a simple linear expression that assumes a current-independent penetration field for i > 0.2. We further show the measured Bth curves at different temperatures normalized by critical current density collapse into one common curve. The above result implies that Dynamic Resistance in coated conductors at different temperatures under perpendicular AC magnetic fields can be scaled simply using measured Ic0 values at those temperatures and analytical equations.Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear ...
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Dynamic Resistance Measurement in a Four-Tape YBCO Stack With Various Applied Field Orientation
IEEE Transactions on Applied Superconductivity, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Jin FangAbstract:The Dynamic Resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on Dynamic Resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of Dynamic Resistance on field angle as well as wire I c ( B , θ ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of Dynamic Resistance on these parameters. Finally, we compared the measured Dynamic Resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the Dynamic Resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. I c ( B , θ ) influences Dynamic Resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers.
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Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires
Superconductor Science and Technology, 2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:© 2018 IOP Publishing Ltd. The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical Resistance can be observed, commonly referred to as 'Dynamic Resistance.' Dynamic Resistance is relevant to many potential higherature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the Dynamic Resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such Dynamic Resistance, including its relationship with the applied current and field, the wire's superconducting properties, the threshold field above which Dynamic Resistance is generated and the flux-flow Resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the Dynamic Resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The Dynamic Resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow Resistance occurs.
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Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
Zhenan Jiang - One of the best experts on this subject based on the ideXlab platform.
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Numerical Modelling of Dynamic Resistance in a Parallel-Connected Stack of HTS Coated-Conductor Tapes
IEEE Transactions on Applied Superconductivity, 2020Co-Authors: Justin M. Brooks, Zhenan Jiang, Rodney A. Badcock, Mark D. Ainslie, Stuart C. Wimbush, Chris W. BumbyAbstract:Dynamic Resistance is observed in type-II superconductors carrying a DC transport current while simultaneously exposed to an alternating magnetic field. The appearance of a nonzero Resistance is attributed to the interaction between the transport current and moving fluxons. This effect is relevant to many superconductor applications such as high-temperature-superconductor (HTS) flux pumps, DC/AC magnets, synchronous machines, and persistent current switches. Here, we present a finite element method (FEM) analysis of both the time averaged Dynamic Resistance and the instantaneous current sharing behaviour in a cable comprised of a stack of four YBCO thin films connected in parallel. Numerical modelling was performed using the H-formulation method implemented in the commercial software COMSOL. The model employs experimentally measured values of the angular dependence of the critical current I.(B, 8) and the flux creep exponent n(B, 8). A single threshold field is observed, above which a finite Dynamic Resistance is observed in all tapes simultaneously. The time-averaged Dynamic Resistance of individual tapes tends to be larger for the exterior tapes than the interior tapes, but this difference decreases as the total transport current in the cable increases. We attribute this to shielding currents flowing in the exterior tapes during the majority of the cycle, which displace net DC current into the interior tapes. However, the relative proportion of DC transport current flowing in the exterior and interior tapes is also observed to vary periodically once per half cycle of the applied field. This is due to the periodic trapping of return screening currents in the interior tapes.
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Dynamic Resistance measurement in a YBCO wire under perpendicular magnetic field at various operating temperatures
Journal of Applied Physics, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Gennady Sidorov, Jin FangAbstract:Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear Mikitik and Brandt equation for i ≤ 0.2 and with a simple linear expression that assumes a current-independent penetration field for i > 0.2. We further show the measured Bth curves at different temperatures normalized by critical current density collapse into one common curve. The above result implies that Dynamic Resistance in coated conductors at different temperatures under perpendicular AC magnetic fields can be scaled simply using measured Ic0 values at those temperatures and analytical equations.Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear ...
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Dynamic Resistance Measurement in a Four-Tape YBCO Stack With Various Applied Field Orientation
IEEE Transactions on Applied Superconductivity, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Jin FangAbstract:The Dynamic Resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on Dynamic Resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of Dynamic Resistance on field angle as well as wire I c ( B , θ ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of Dynamic Resistance on these parameters. Finally, we compared the measured Dynamic Resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the Dynamic Resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. I c ( B , θ ) influences Dynamic Resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers.
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Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires
Superconductor Science and Technology, 2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:© 2018 IOP Publishing Ltd. The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical Resistance can be observed, commonly referred to as 'Dynamic Resistance.' Dynamic Resistance is relevant to many potential higherature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the Dynamic Resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such Dynamic Resistance, including its relationship with the applied current and field, the wire's superconducting properties, the threshold field above which Dynamic Resistance is generated and the flux-flow Resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the Dynamic Resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The Dynamic Resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow Resistance occurs.
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Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
Naoyuki Amemiya - One of the best experts on this subject based on the ideXlab platform.
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Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires
Superconductor Science and Technology, 2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:© 2018 IOP Publishing Ltd. The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical Resistance can be observed, commonly referred to as 'Dynamic Resistance.' Dynamic Resistance is relevant to many potential higherature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the Dynamic Resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such Dynamic Resistance, including its relationship with the applied current and field, the wire's superconducting properties, the threshold field above which Dynamic Resistance is generated and the flux-flow Resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the Dynamic Resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The Dynamic Resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow Resistance occurs.
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Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
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The Dynamic Resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation
Superconductor Science and Technology, 2018Co-Authors: Zhenan Jiang, Naoyuki Amemiya, Jin Fang, Wei Zhou, Min Yao, Chris W. BumbyAbstract:Dynamic Resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of Dynamic Resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ~12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured Dynamic Resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the Dynamic Resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured Dynamic Resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the Dynamic Resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles.
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Dynamic Resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K
Superconductor Science and Technology, 2017Co-Authors: Zhenan Jiang, Ryuki Toyomoto, Naoyuki Amemiya, Xingyou Zhang, Chris W. BumbyAbstract:Superconducting high-T c coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'Dynamic Resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of Dynamic Resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the Dynamic Resistance in perpendicular field. This approach implies a linear relationship between Dynamic Resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC Resistance includes an additional nonlinear term which is due to flux-flow Resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the Dynamic Resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines.
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Dynamic Resistance Measurements in a GdBCO-Coated Conductor
IEEE Transactions on Applied Superconductivity, 2017Co-Authors: Zhenan Jiang, Ryuki Toyomoto, Naoyuki Amemiya, Chris W. Bumby, Rodney A. Badcock, Nicholas J. LongAbstract:Dynamic Resistance is a phenomenon which occurs when a superconducting wire carries dc transport current whilst experiencing an alternating magnetic field. This situation occurs in a range of HTS machinery applications, where Dynamic Resistance can lead to large parasitic heat loads and potential quench events. Here, we present Dynamic Resistance measurements of a 5-mm-wide Fujikura coated conductor wire at 77 K. We report experimental values obtain through varying the field angle (the angle between magnetic field and normal vector of the conductor wide-face), the dc current levels, and the magnetic field amplitude, and frequency. We show that the Dynamic Resistance in perpendicular magnetic field can be predicted by using a simple analytical equation. We also show that across the range of field angles measured here the Dynamic Resistance is dominated by the perpendicular component of the applied magnetic field.
Jin Fang - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Resistance measurement in a YBCO wire under perpendicular magnetic field at various operating temperatures
Journal of Applied Physics, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Gennady Sidorov, Jin FangAbstract:Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear Mikitik and Brandt equation for i ≤ 0.2 and with a simple linear expression that assumes a current-independent penetration field for i > 0.2. We further show the measured Bth curves at different temperatures normalized by critical current density collapse into one common curve. The above result implies that Dynamic Resistance in coated conductors at different temperatures under perpendicular AC magnetic fields can be scaled simply using measured Ic0 values at those temperatures and analytical equations.Dynamic Resistance plays an important role in certain high-Tc superconducting (HTS) applications where an HTS coated conductor carries a DC current exposed to an AC magnetic field. Here, we report measurements of the Dynamic Resistance in a 4 mm-wide YBCO coated conductor under a perpendicular AC magnetic field at 77 K, 70 K, and 65 K. Dynamic Resistance was measured at three different frequencies for the reduced current, i (It/Ic0), ranging from 0.04 to 0.9, where It is the DC current level and Ic0 is the self-field critical current of the conductor at each temperature. At all three temperatures, the threshold magnetic field (Bth) values increase with reducing DC current. These results show that, for a given set of applied conditions, Dynamic Resistance decreases with decreasing operating temperature, which we attribute to the temperature dependent increase in the critical current of the wire. We show that measured Bth values at all three temperatures agree well with the analytical values from nonlinear ...
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Dynamic Resistance Measurement in a Four-Tape YBCO Stack With Various Applied Field Orientation
IEEE Transactions on Applied Superconductivity, 2019Co-Authors: Yanchao Liu, Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Jin FangAbstract:The Dynamic Resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on Dynamic Resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of Dynamic Resistance on field angle as well as wire I c ( B , θ ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of Dynamic Resistance on these parameters. Finally, we compared the measured Dynamic Resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the Dynamic Resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. I c ( B , θ ) influences Dynamic Resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers.
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The Dynamic Resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation
Superconductor Science and Technology, 2018Co-Authors: Zhenan Jiang, Naoyuki Amemiya, Jin Fang, Wei Zhou, Min Yao, Chris W. BumbyAbstract:Dynamic Resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of Dynamic Resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ~12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured Dynamic Resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the Dynamic Resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured Dynamic Resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the Dynamic Resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles.
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Dynamic Resistance Measurement of a Four-Tape YBCO Stack in a Perpendicular Magnetic Field
IEEE Transactions on Applied Superconductivity, 2018Co-Authors: Zhenan Jiang, Chris W. Bumby, Rodney A. Badcock, Nicholas J. Long, Wei Zhou, Mike Staines, Jin FangAbstract:Dynamic Resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on Dynamic Resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the Dynamic Resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack.
Ryuki Toyomoto - One of the best experts on this subject based on the ideXlab platform.
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Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires
Superconductor Science and Technology, 2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:© 2018 IOP Publishing Ltd. The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical Resistance can be observed, commonly referred to as 'Dynamic Resistance.' Dynamic Resistance is relevant to many potential higherature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the Dynamic Resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such Dynamic Resistance, including its relationship with the applied current and field, the wire's superconducting properties, the threshold field above which Dynamic Resistance is generated and the flux-flow Resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the Dynamic Resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The Dynamic Resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow Resistance occurs.
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Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
2018Co-Authors: Mark D. Ainslie, Zhenan Jiang, Ryuki Toyomoto, Chris W. Bumby, Naoyuki AmemiyaAbstract:Research data supporting [Numerical modelling of Dynamic Resistance in high-temperature superconducting coated-conductor wires]
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Dynamic Resistance of a high-T c coated conductor wire in a perpendicular magnetic field at 77 K
Superconductor Science and Technology, 2017Co-Authors: Zhenan Jiang, Ryuki Toyomoto, Naoyuki Amemiya, Xingyou Zhang, Chris W. BumbyAbstract:Superconducting high-T c coated conductor (CC) wires comprise a ceramic thin film with a large aspect ratio. This geometry can lead to significant dissipative losses when exposed to an alternating magnetic field. Here we report experimental measurements of the 'Dynamic Resistance' of commercially available SuperPower and Fujikura CC wires in an AC perpendicular field. The onset of Dynamic Resistance occurs at a threshold field amplitude, which is determined by the total DC transport current and the penetration field of the conductor. We show that the field-dependence of the normalised magnetisation loss provides an unambiguous value for this threshold field at zero transport current. From this insight we then obtain an expression for the Dynamic Resistance in perpendicular field. This approach implies a linear relationship between Dynamic Resistance and applied field amplitude, and also between threshold field and transport current and this is consistent with our experimental data. The analytical expression obtained yields values that closely agree with measurements obtained across a wide range of frequencies and transport currents, and for multiple CC wires produced by different wire manufacturers and with significantly differing dimensions and critical currents. We further show that at high transport currents, the measured DC Resistance includes an additional nonlinear term which is due to flux-flow Resistance incurred by the DC transport current. This occurs once the field-dependent critical current of the wire falls below the DC transport current for part of each field cycle. Our results provide an effective and simple approach to calculating the Dynamic Resistance of a CC wire, at current and field magnitudes consistent with those expected in superconducting machines.
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Dynamic Resistance Measurements in a GdBCO-Coated Conductor
IEEE Transactions on Applied Superconductivity, 2017Co-Authors: Zhenan Jiang, Ryuki Toyomoto, Naoyuki Amemiya, Chris W. Bumby, Rodney A. Badcock, Nicholas J. LongAbstract:Dynamic Resistance is a phenomenon which occurs when a superconducting wire carries dc transport current whilst experiencing an alternating magnetic field. This situation occurs in a range of HTS machinery applications, where Dynamic Resistance can lead to large parasitic heat loads and potential quench events. Here, we present Dynamic Resistance measurements of a 5-mm-wide Fujikura coated conductor wire at 77 K. We report experimental values obtain through varying the field angle (the angle between magnetic field and normal vector of the conductor wide-face), the dc current levels, and the magnetic field amplitude, and frequency. We show that the Dynamic Resistance in perpendicular magnetic field can be predicted by using a simple analytical equation. We also show that across the range of field angles measured here the Dynamic Resistance is dominated by the perpendicular component of the applied magnetic field.
