A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet dur...A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.展开更多
The no-insulation(NI)winding approach can remarkably improve the thermal stability of high-temperature superconducting coil.However,mechanical issues have gradually become a key factor to block the development of NI m...The no-insulation(NI)winding approach can remarkably improve the thermal stability of high-temperature superconducting coil.However,mechanical issues have gradually become a key factor to block the development of NI magnets in recent years.This paper mainly analyzes the effect of the overband on the mechanical behaviors of an NI coil during a quench.A numerical model including a quench model combined with a three-dimensional homogeneous mechanical model is employed to study the change of stress in the coil without and with the over band during a local quench.The results show that the overband has an obvious effect on the stress distribution as the heater is located at the outer turn of the coil.Meanwhile,the values of stress in the coil are also affected by the overband.Moreover,the effects of the thickness of the overband and the location of the heater on the mechanical behaviors of the coil are also discussed.It is worth noting that the overband can remarkably reduce the hoop and axial tensile stresses of the coil during a quench。展开更多
The parallel-wound technique is an effective method for reducing charging delay and enhancing electromagnetic margin of no-insulation high-temperature superconducting(NI HTS)coils,as demonstrated by both experiments a...The parallel-wound technique is an effective method for reducing charging delay and enhancing electromagnetic margin of no-insulation high-temperature superconducting(NI HTS)coils,as demonstrated by both experiments and numerical simulations.From an engineering standpoint,the parallel-wound design also mitigates the constraint of individual conductor length,which is a significant limitation in large-scale coils requiring a single continuous conductor of the same specifications.However,traditional electromagnetic modeling of parallel-wound no-insulation(PWNI)HTS coils relies on equivalent circuit models,and a combined finite element model is required to capture the screening current characteristics of HTS coated conductors.The mutual invo-cation between circuit models and finite element models increases the technical demands on simulation engi-neers and complicates the analysis of electromagnetic interactions with other physical fields.To address these challenges,we first propose an axisymmetric distributed equivalent circuit model for PWNI HTS double pancake(DP)coils.The equivalent circuit model is then integrated directly into the finite element framework of T-A formulation,resulting in a streamlined electromagnetic finite element model.The validity of this model is confirmed through the charging and discharging experiments with a dual-wound NI HTS coil.Utilizing this model,we further investigate the effects of joint resistance and turn-to-turn contact resistivity on the electro-magnetic characteristics of PWNI HTS coils.Additionally,the excitation loss and stress of multiple PWNI HTS DP coils in a 35 T all-superconducting high field magnet are also analyzed.The results indicate that both the lower turn-to-turn contact resistivity and joint resistance may lead to significant non-uniform currents within the coil.The joint resistance has a significant impact on the critical current of PWNI HTS coils,and the optimization of energization methodology increased the critical current of the experimental coil by 12 A.Enhancing the equivalent radial resistance between bundled turns proves more effective for reducing charging delay of PWNI coil than increasing that within bundled turns.Multiple PWNI coils in high field magnet exhibit elevated losses relative to single-tape equivalents due to coupling currents,particularly during the initial excitation.However,their peak strain accumulation is marginally lower than that of single-wound configuration.展开更多
No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel...No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel stacked-tape structure leads to new current redistribution among stacked tapes in each turn during local quenches,which also considerably changes the current redistribution behavior through inter-turn contacts.Therefore,quench behaviors of parallel-wound no-insulation(PWNI)coil should differ from its counterpart wound with single tape,which are still unknown.This study is to illustrate quench behaviors of PWNI HTS coils induced by local hot spot.A multi-physics model integrating an equivalent circuit network,a FEM heat transfer module,and a FEM T-A model is developed to analyze the electromagnetic and thermal characteristics of PWNI HTS coils during quench.Results show that the transport currents are mainly redistributed among parallel-stacked tapes through terminal resistances when a local hot spot happens on one tape,while being less dependent on turn-to-turn electrical contacts.It leads to a coupling current within PWNI coils that is not present in NI coils wound with single tape(single-wound no-insulation(SWNI)coil),resulting in a highly non-uniform transport current distribution among parallel-wound tapes.The reduced terminal joint resistances further enhance the coupling current,potentially leading to an extra overcurrent quench risk in PWNI coils.Moreover,the current redistribution between parallel-stacked tapes inhibits the turn-to-turn current redistribution in the PWNI coil,thus significantly reducing its magnetic field degradation under a high heat disturbance,which can be almost less than half of the SWNI counterpart in this study.These results offer important theoretical guidance to safety operation and robustness improvement of high-field HTS magnets wound by PWNI technique.展开更多
Applied-field magnetoplasmadynamic(AF-MPD)thrusters have been proposed as highly propellant-efficient thrusters for satellites and spacecraft.The electromagnets for these devices have only been reducible to practical ...Applied-field magnetoplasmadynamic(AF-MPD)thrusters have been proposed as highly propellant-efficient thrusters for satellites and spacecraft.The electromagnets for these devices have only been reducible to practical dimensions with the maturation of high-temperature superconductors.We report the development and ground testing of such a magnet which has been designed and constructed with the intention of deploying to the International Space Station and testing in orbit.The magnet is of dimensions suitable for accommodating a small thruster,will be cooled by a miniature space-compatible cryocooler and energized by a flux pump.It can generate a magnetic field of up to 760 mT operating at around 77 K in that configuration.A passive magnetic shield has been incorporated in order to comply with stray-field requirements of the ISS when operating at the target operational field of 300 mT.展开更多
High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increa...High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increased ramp time is a known disadvantage of the NI approach. To solve this problem, a proportional and integral(PI) active feedback control has been proposed in the charging experiments of the NI magnet. In this study, the electromagnetic-thermal-mechanical characteristics of an NI magnet with and without PI are analyzed to ensure the safety and reliability of PI control. Due to the increase in the radial current of the magnet, the turn-to-turn loss energy of the magnet with PI is more than twice that without PI. However, the magnetization loss energy of the magnet has a small difference with and without PI. It can be also found that the NI magnet with PI has a large temperature rise, and thus it has a low thermal stability margin. Moreover, in the high field, the hoop stress and hoop strain peaks of a magnet with PI are larger than those without PI. Thus, PI control can induce a relatively high risk of mechanical damage in the applications of NI magnets.展开更多
基金the National Natural Science Foundation of China(Nos.11932008 and 11672120)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-kb01)。
文摘A transient multi-physics model incorporated with an electromagneto-thermomechanical coupling is developed to capture the multi-field behavior of a single-pancake(SP)insert no-insulation(NI)coil in a hybrid magnet during the charging and discharging processes.The coupled problem is resolved by means of the finite element method(FEM)for the magneto-thermo-elastic behaviors and the Runge-Kutta method for the transient responses of the electrical circuits of the hybrid superconducting magnet system.The results reveal that the transient multi-physics responses of the insert NI coil primarily depend on the charging/discharging procedure of the hybrid magnet.Moreover,a reverse azimuthal current and a compressive hoop stress are induced in the insert NI coil during the charging process,while a forward azimuthal current and a tensile hoop stress are observed during the discharging process.The induced voltages in the insert NI coil can drive the currents flowing across the radial turns where the contact resistance exists.Therefore,it brings forth significant Joule heat,causing a temperature rise and a uniform distribution of this heat in the coil turns.Accordingly,a thermally/mechanically unstable or quenching event may be encountered when a high operating current is flowing in the insert NI coil.It is numerically predicted that a quick charging will induce a compressive hoop stress which may bring a risk of buckling instability in the coil,while a discharging will not.The simulations provide an insight of hybrid superconducting magnets under transient start-up or shutdown phases which are inevitably encountered in practical applications.
基金The authors acknowledge the supports from the National Natural Science Foundation of China(No.11872195)the Fundamental Research Funds for the Central Universities(lzujbky-2020-1)Science and Technology on Ship Integrated Power System Technology Laboratory(No.6142217190).
文摘The no-insulation(NI)winding approach can remarkably improve the thermal stability of high-temperature superconducting coil.However,mechanical issues have gradually become a key factor to block the development of NI magnets in recent years.This paper mainly analyzes the effect of the overband on the mechanical behaviors of an NI coil during a quench.A numerical model including a quench model combined with a three-dimensional homogeneous mechanical model is employed to study the change of stress in the coil without and with the over band during a local quench.The results show that the overband has an obvious effect on the stress distribution as the heater is located at the outer turn of the coil.Meanwhile,the values of stress in the coil are also affected by the overband.Moreover,the effects of the thickness of the overband and the location of the heater on the mechanical behaviors of the coil are also discussed.It is worth noting that the overband can remarkably reduce the hoop and axial tensile stresses of the coil during a quench。
基金supported by the Natural Science Foundation of China(Grant No.52325701,52293421,52293422,52277032)Beijing Nova Program(20220484102).
文摘The parallel-wound technique is an effective method for reducing charging delay and enhancing electromagnetic margin of no-insulation high-temperature superconducting(NI HTS)coils,as demonstrated by both experiments and numerical simulations.From an engineering standpoint,the parallel-wound design also mitigates the constraint of individual conductor length,which is a significant limitation in large-scale coils requiring a single continuous conductor of the same specifications.However,traditional electromagnetic modeling of parallel-wound no-insulation(PWNI)HTS coils relies on equivalent circuit models,and a combined finite element model is required to capture the screening current characteristics of HTS coated conductors.The mutual invo-cation between circuit models and finite element models increases the technical demands on simulation engi-neers and complicates the analysis of electromagnetic interactions with other physical fields.To address these challenges,we first propose an axisymmetric distributed equivalent circuit model for PWNI HTS double pancake(DP)coils.The equivalent circuit model is then integrated directly into the finite element framework of T-A formulation,resulting in a streamlined electromagnetic finite element model.The validity of this model is confirmed through the charging and discharging experiments with a dual-wound NI HTS coil.Utilizing this model,we further investigate the effects of joint resistance and turn-to-turn contact resistivity on the electro-magnetic characteristics of PWNI HTS coils.Additionally,the excitation loss and stress of multiple PWNI HTS DP coils in a 35 T all-superconducting high field magnet are also analyzed.The results indicate that both the lower turn-to-turn contact resistivity and joint resistance may lead to significant non-uniform currents within the coil.The joint resistance has a significant impact on the critical current of PWNI HTS coils,and the optimization of energization methodology increased the critical current of the experimental coil by 12 A.Enhancing the equivalent radial resistance between bundled turns proves more effective for reducing charging delay of PWNI coil than increasing that within bundled turns.Multiple PWNI coils in high field magnet exhibit elevated losses relative to single-tape equivalents due to coupling currents,particularly during the initial excitation.However,their peak strain accumulation is marginally lower than that of single-wound configuration.
基金sponsored by National Key R&D Program of China(No.2023YFE0118100)The work is also sponsored by National Natural Science Foundation of China(No.52207028)+1 种基金The work is also spon-sored by Shanghai Science&Technology Innovation Action Program(No.23511101800)The work is also sponsored by Natural Science Foundation of Chongqing(No.2022NSCQ-MSX1512).
文摘No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel stacked-tape structure leads to new current redistribution among stacked tapes in each turn during local quenches,which also considerably changes the current redistribution behavior through inter-turn contacts.Therefore,quench behaviors of parallel-wound no-insulation(PWNI)coil should differ from its counterpart wound with single tape,which are still unknown.This study is to illustrate quench behaviors of PWNI HTS coils induced by local hot spot.A multi-physics model integrating an equivalent circuit network,a FEM heat transfer module,and a FEM T-A model is developed to analyze the electromagnetic and thermal characteristics of PWNI HTS coils during quench.Results show that the transport currents are mainly redistributed among parallel-stacked tapes through terminal resistances when a local hot spot happens on one tape,while being less dependent on turn-to-turn electrical contacts.It leads to a coupling current within PWNI coils that is not present in NI coils wound with single tape(single-wound no-insulation(SWNI)coil),resulting in a highly non-uniform transport current distribution among parallel-wound tapes.The reduced terminal joint resistances further enhance the coupling current,potentially leading to an extra overcurrent quench risk in PWNI coils.Moreover,the current redistribution between parallel-stacked tapes inhibits the turn-to-turn current redistribution in the PWNI coil,thus significantly reducing its magnetic field degradation under a high heat disturbance,which can be almost less than half of the SWNI counterpart in this study.These results offer important theoretical guidance to safety operation and robustness improvement of high-field HTS magnets wound by PWNI technique.
基金supported by the New Zealand Ministry of Business,Innovation and Employment under contract RTVU2003.
文摘Applied-field magnetoplasmadynamic(AF-MPD)thrusters have been proposed as highly propellant-efficient thrusters for satellites and spacecraft.The electromagnets for these devices have only been reducible to practical dimensions with the maturation of high-temperature superconductors.We report the development and ground testing of such a magnet which has been designed and constructed with the intention of deploying to the International Space Station and testing in orbit.The magnet is of dimensions suitable for accommodating a small thruster,will be cooled by a miniature space-compatible cryocooler and energized by a flux pump.It can generate a magnetic field of up to 760 mT operating at around 77 K in that configuration.A passive magnetic shield has been incorporated in order to comply with stray-field requirements of the ISS when operating at the target operational field of 300 mT.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11872195, and 11932008)Fundamental Research Funds for the Central Universities (Grant No. lzujbky-2020-1)。
文摘High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increased ramp time is a known disadvantage of the NI approach. To solve this problem, a proportional and integral(PI) active feedback control has been proposed in the charging experiments of the NI magnet. In this study, the electromagnetic-thermal-mechanical characteristics of an NI magnet with and without PI are analyzed to ensure the safety and reliability of PI control. Due to the increase in the radial current of the magnet, the turn-to-turn loss energy of the magnet with PI is more than twice that without PI. However, the magnetization loss energy of the magnet has a small difference with and without PI. It can be also found that the NI magnet with PI has a large temperature rise, and thus it has a low thermal stability margin. Moreover, in the high field, the hoop stress and hoop strain peaks of a magnet with PI are larger than those without PI. Thus, PI control can induce a relatively high risk of mechanical damage in the applications of NI magnets.
