Charging process simulation of a coil by a self-regulating high-T_(c)superconducting flux pump

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.

A superconducting wireless energiser based on electromechanical energy conversion

A superconducting magnet(SM)can produce high magnetic fields up to a dozen times stronger than those generated by an electromagnet made of normal conductors or a permanent magnet(PM),and thus has attracted increasing research efforts in many domains including medical devices,large scientific equipment,transport,energy storage,power systems,and electric machines.Wireless energisers,e.g.,high temperature superconducting(HTS)flux pumps,can eliminate the thermal load from current leads and arc erosion of slip rings,and are thus considered a promising energisation tool for SMs.However,the time‐averaged DC output voltage in existing HTS flux pumps is generated by dynamic resistance:the dynamic loss is unavoidable,and the total AC loss will become significant at high frequencies.This study introduces a highly efficient superconducting wireless energizer(SWE)designed specifically for SMs.The SWE takes advantage of the inherent properties of a superconducting loop,including flux conservation and zero DC resistivity.Extensive theoretical analysis,numerical modelling exploiting the H‐ϕformulation,and experimental measurements were conducted to demonstrate the efficiency and efficacy of the novel SWE design.The electromechanical performance and loss characteristics of the SWE system have also been investigated.Compared to conventional HTS flux pumps,the proposed SWE has lower excitation loss,in the order of 10−1 mW,and thus can achieve a high system efficiency of no less than 95%.Furthermore,it has a simpler structure with higher reliability,considered ready for further industrial development.In addition to deepening the understating of the intricate electromechanical dynamics between magnetic dipoles and superconducting circuits,this article provides a novel wireless energisation technique for SMs and opens the way to step changes in future electric transport and energy sectors.

Time-dependent development of dynamic resistance voltage of superconducting tape considering heat accumulation

In flux pumps,motors and superconducting magnets,the high temperature superconductor(HTS)coated conductor frequently carries a DC transport current when an oscillating magnetic field is present in the background.Under this circumstance,the interesting effect of dynamic resistance takes place,which can affect the operating performance of superconducting devices:heat accumulation can contribute to the rising temperature of the HTS tape and the dynamic resistance voltage can change accordingly.This article explores the time‐dependent development of the dynamic resistance voltage using a numerical modeling considering the thermal effects.After a validation against experimental results,this work investigates the effects of several factors on the structure of the HTS tape on the time‐dependent development of the dynamic resistance,thus providing insights toward a better understanding of the time‐dependent behavior of HTS tapes under external magnetic fields.

Magnetic bearings with double crossed loops modelled with T-A formulation and electric circuits

The application of High‐Temperature Superconductor(HTS)coils made of coated conductors has been investigated for many years.A possible configuration for such coils is the jointless loop,also known as the ring coil.The double crossed loop coil(DCLC)has been successfully applied in superconducting magnetic bearings(SMBs).The design of SMBs with DCLCs requires flexible modelling to allow all parts of the device to be represented.This work proposes the T‐A formulation with a thin‐film approximation for modelling SMB with DCLCs in the finite element analysis framework.A 2D representation of the system is coupled with an external electric circuit to model the continuity of the lines that represent the parts of each jointless loop.To couple the T‐A formulation and the circuit,an average of the total electric field,with both resistive and inductive components,is applied to the circuit.The total current computed by the circuit is applied to the T‐A formulation.The proposed methodology was validated by comparison with levitation force experimental data.Two types of tests were simulated:five levitation force tests and three guidance force tests.It is shown that there is a limit to the behaviour of the levitation force related to the high‐loss state.Below this limit,the stack of DCLCs behaves as an equivalent bulk.Beyond this limit,a high‐loss state appears as a linear growth of the levitation force.It is also shown that this high‐loss state in vertical displacement influences the lateral force.

A statistical model for the design of rotary HTS flux pumps based on deep-learning neuron network

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.