Rotory high temperature superconducting(HTS)flux pumps can consistently generate a DC voltage by rotating magnets over superconducting tapes,and thus energize the circuit if a closed loop is formed.The voltage output ...Rotory high temperature superconducting(HTS)flux pumps can consistently generate a DC voltage by rotating magnets over superconducting tapes,and thus energize the circuit if a closed loop is formed.The voltage output is a crucial factor to reflect the performance of such an HTS flux pump,which is determined by a set of design specifications,and some of them have been investigated extensively in the current literature.However,no work has been done yet to study the HTS dynamo output voltage by efficiently integrating all the design parameters together.In this paper,a well‐trained deep‐learning neuron network(DNN)with back‐propagation algorithms has been put forward and validated.The proposed DNN is capable of quantifying the output voltage of an HTS dynamo instantly with an overall accuracy of approximately 98%with respect to the simulated values with all design parameters explicitly specified.The model possesses a powerful ability to characterize the output behavior of HTS dynamos by considering multiple design parameters,e.g.,airgap,superconductor tape width,operating frequency,remanent flux density,rotor radius,and permanent magnet width,which have covered all the typical design considerations.The output characteristics of an HTS dynamo against each of the design parameters have been successfully demonstrated using this model.Compared to conventional time‐consuming finite element method(FEM)based numerical models,the proposed DNN model has the advantages of automatic learning,fast computation,as well as strong programmability.Therefore the DNN model can greatly facilitate the design and optimization process for HTS dynamos.An executable application has been developed accordingly based on the DNN model,which is believed to provide a useful tool for learners and designers of HTS dynamos.展开更多
Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by ...Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by a self‐regulating HTS flux pump is examined in detail by numerical modeling.The proposed model combines an H‐formulation finite element method(FEM)model with an electrical circuit,enabling a comprehensive evaluation of the overall performance of self‐regulating HTS flux pumps while accurately capturing local effects.The results indicate that the proposed model can capture all the critical features of a self‐regulating HTS flux pump,including superconducting properties and the impact of the secondary resistance.When the numerical results are compared to the experimental data,the presented model is found to be acceptable both qualitatively and quantitatively.Based on this model,we have demonstrated how the addition of a milliohm range,normal‐conducting secondary resistance in series with the charging loop can improve the charging process.In addition,its impact on the charging performance is revealed,including the maximum achievable current,charging speed,and the generated losses.The modeling approach employed in this study can be generalized to the optimization and design of various types of flux pumps,potentially expediting their practical application.展开更多
For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against...For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against the reported AC‐losses measurements on single‐phase cables provided by the Russian Scientific and Research Institute of the Cable Industry(VNIIKP).Four models are presented,the first being a single‐phase cable of 50 tapes and the others being three triaxial cables made of up to 135 coated conductors distributed in up to 9 layers.A systematic study is devised,where the number of layers per phase increases from 1 to 3,with at least 14 tapes distributed across each layer of the first(innermost)phase,15 in the secondary(middle)phase,and 16 in the third(outermost)phase,respectively.Remarkably,our results reveal that the simple strategy of considering an unbalanced distribution for the amplitudes of the applied current,can generally balance the magnetic field between the three phases even for the bilayer and trilayer cables,resulting in negligible magnetic leaks in all situations.Besides,our high‐resolution simulations allow to see for the first time how the transport and magnetization currents distribute across the thickness of all the superconducting tapes,from which we have found that the AC‐losses of the 2nd phase is generally higher than at the other phases at low to moderate transport currents,I_(tr)<0:8I c,being I_(c) the critical current of the corresponding tapes.Nevertheless,depending on whether the I_(c) of the SC tapes at the 3rd phase layers is lower than the one at the 2nd phase,the layers at the third phase can exhibit a considerable increment on the AC losses.This is result of the considered magneto angular anisotropy of the superconducting tapes,which lead to intriguing electromagnetic features that suggest a practical threshold for the applied transport current,being it 0:8I_(c).Likewise,the relative change in the AC‐losses per adding layers,per phase,and as a function of the entire range of applied transport current is disclosed.展开更多
AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the m...AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere‐turns.In this work,we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower REBCO coated conductors,for fast‐ramping application with the same Ampere‐turns to identify the lowest AC loss among them.The HTS magnets have a total turn number of 50 and inner diameter of 30 cm,carrying AC current operating in the temperature range of 20–40 K at 25 Hz.We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils,grading Ic values for the solenoid configuration,and applying flux diverters to shape the magnetic field around the coil windings.The simulation was implemented using a homogenized H‐formulation.Across all studied loss reduction methods,the use of flux diverters has the largest impact in AC loss reduction.The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn‐to‐turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn‐to‐turn gap with the flux diverters.Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field.展开更多
文摘Rotory high temperature superconducting(HTS)flux pumps can consistently generate a DC voltage by rotating magnets over superconducting tapes,and thus energize the circuit if a closed loop is formed.The voltage output is a crucial factor to reflect the performance of such an HTS flux pump,which is determined by a set of design specifications,and some of them have been investigated extensively in the current literature.However,no work has been done yet to study the HTS dynamo output voltage by efficiently integrating all the design parameters together.In this paper,a well‐trained deep‐learning neuron network(DNN)with back‐propagation algorithms has been put forward and validated.The proposed DNN is capable of quantifying the output voltage of an HTS dynamo instantly with an overall accuracy of approximately 98%with respect to the simulated values with all design parameters explicitly specified.The model possesses a powerful ability to characterize the output behavior of HTS dynamos by considering multiple design parameters,e.g.,airgap,superconductor tape width,operating frequency,remanent flux density,rotor radius,and permanent magnet width,which have covered all the typical design considerations.The output characteristics of an HTS dynamo against each of the design parameters have been successfully demonstrated using this model.Compared to conventional time‐consuming finite element method(FEM)based numerical models,the proposed DNN model has the advantages of automatic learning,fast computation,as well as strong programmability.Therefore the DNN model can greatly facilitate the design and optimization process for HTS dynamos.An executable application has been developed accordingly based on the DNN model,which is believed to provide a useful tool for learners and designers of HTS dynamos.
文摘Self‐regulating high‐temperature superconducting(HTS)flux pumps enable direct current injection into a closed‐loop superconducting coil without any electrical contact.In this work,the process of charging a coil by a self‐regulating HTS flux pump is examined in detail by numerical modeling.The proposed model combines an H‐formulation finite element method(FEM)model with an electrical circuit,enabling a comprehensive evaluation of the overall performance of self‐regulating HTS flux pumps while accurately capturing local effects.The results indicate that the proposed model can capture all the critical features of a self‐regulating HTS flux pump,including superconducting properties and the impact of the secondary resistance.When the numerical results are compared to the experimental data,the presented model is found to be acceptable both qualitatively and quantitatively.Based on this model,we have demonstrated how the addition of a milliohm range,normal‐conducting secondary resistance in series with the charging loop can improve the charging process.In addition,its impact on the charging performance is revealed,including the maximum achievable current,charging speed,and the generated losses.The modeling approach employed in this study can be generalized to the optimization and design of various types of flux pumps,potentially expediting their practical application.
基金supported by the UK Research and Innovation,Engineering and Physical Sciences Research Council(EPSRC),grant Ref.EP/S025707/1,led by H.S.R.
文摘For an accurate estimation of the AC losses of superconducting triaxial cables,in this paper we present a two‐dimensional model capable to provide a global assessment of multi‐layer triaxial cables,validated against the reported AC‐losses measurements on single‐phase cables provided by the Russian Scientific and Research Institute of the Cable Industry(VNIIKP).Four models are presented,the first being a single‐phase cable of 50 tapes and the others being three triaxial cables made of up to 135 coated conductors distributed in up to 9 layers.A systematic study is devised,where the number of layers per phase increases from 1 to 3,with at least 14 tapes distributed across each layer of the first(innermost)phase,15 in the secondary(middle)phase,and 16 in the third(outermost)phase,respectively.Remarkably,our results reveal that the simple strategy of considering an unbalanced distribution for the amplitudes of the applied current,can generally balance the magnetic field between the three phases even for the bilayer and trilayer cables,resulting in negligible magnetic leaks in all situations.Besides,our high‐resolution simulations allow to see for the first time how the transport and magnetization currents distribute across the thickness of all the superconducting tapes,from which we have found that the AC‐losses of the 2nd phase is generally higher than at the other phases at low to moderate transport currents,I_(tr)<0:8I c,being I_(c) the critical current of the corresponding tapes.Nevertheless,depending on whether the I_(c) of the SC tapes at the 3rd phase layers is lower than the one at the 2nd phase,the layers at the third phase can exhibit a considerable increment on the AC losses.This is result of the considered magneto angular anisotropy of the superconducting tapes,which lead to intriguing electromagnetic features that suggest a practical threshold for the applied transport current,being it 0:8I_(c).Likewise,the relative change in the AC‐losses per adding layers,per phase,and as a function of the entire range of applied transport current is disclosed.
基金supported in part by New Zealand Ministry of Business,Innovation and Employment(MBIE)by the Strategic Science Investment Fund“Advanced Energy Technology Platforms”under Contract RTVU20042020 Google Excellence Research University ProgramUS DOE Ernst Courant Traineeship in Accelerator Sciences and Engineering,the educational program of next generation of accelerator physicists and engineer,US Department of Energy,HEP office.
文摘AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere‐turns.In this work,we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower REBCO coated conductors,for fast‐ramping application with the same Ampere‐turns to identify the lowest AC loss among them.The HTS magnets have a total turn number of 50 and inner diameter of 30 cm,carrying AC current operating in the temperature range of 20–40 K at 25 Hz.We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils,grading Ic values for the solenoid configuration,and applying flux diverters to shape the magnetic field around the coil windings.The simulation was implemented using a homogenized H‐formulation.Across all studied loss reduction methods,the use of flux diverters has the largest impact in AC loss reduction.The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn‐to‐turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn‐to‐turn gap with the flux diverters.Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field.
