Research And Design On GJ-level Fast Discharge Resistor For Quench Protection System Of Large Superconducting Magnet

Comprehensive Research Facility for Fusion Technology(CRAFT)is an important scientific engineering project in China.It will be a comprehensive research platform with the highest parameters and full functionalities in the research area of magnetic confinement fusion around the world.Fast Discharge Resistor(FDR)is one of the key devices in the Quench Protection System(QPS).According to the highest SMC parameters with inductance of 2 H,rated current of 90 kA and rated voltage of 10 kV,the design,analysis,research and development of FDR with GJ level is achieved.Compared with the FDRs in the other QPS of large fusion devices,the developed FDR owns the advantages of highest energy density and lowest stray inductance density as well as the high energy endurance,strong heat dispersion,modularization construction.The main contents and innovations are shown as follow:Based on the comprehensive research of electricity,magnetism and heat,the laminated structure and modularization construction is applied,the modularization and matrix structure of FDR is proposed which owns the resistance of 90 kA/10 kV for the power parameters and 300? for the high heat.The mutual inductance optimization method by reverse laminated resistance tapes is applied,combined with the cooling optimization method under high energy density and mutual inductance coupling method under complex structure,skin effect restraint under large current.In addition,by using the magnetic fields of mutual inductance coupling effect for the FDR under complex magnet field,a structure optimization method for reducing stray inductance is proposed which is on basis of the high energy density.With the FDR design,the technology challenge and design difficulty of high energy density,strong cooling effect and low stray inductance is solved.With the research of difficulties above,the entire GJ-level FDR is analyzed and designed.With the overall function of electromagnetic stress,high thermal expansion and gravity effect,the comprehensive deformation of FDR under complex magnet field is testified based on the insulation support inside resistor slices.On the basis of space thermal distribution under high energy,temperature change under unbalance current and eddy current effect,the thermal stability under high energy density is analyzed.The effect analysis of the QPS under FDR stray inductance is illustrated and the restraint condition of stray inductance is ensured.With the current path analysis under structure optimization,the FDR stray inductance is reduced.Based on the research of FDR,the QPS analysis aiming at protection of SMC is carried out.The secondary commutation technology is compared.The circuit current transferring and change process is analyzed.The QPS plan based on the commutation technology of artificial zero current is developed.In addition,with the FEA tool,the optimized analysis and design on the stray parameters of complex circuit of QPS is implemented.With the research and design,it can provide guidance and foundation of the design the circuit structure which can keep the QPS in safety operation.Through the research and design of FDR above,a series of FDR module machines is manufactured.With the FEA simulation and prototype test results,the dynamic stability,thermal stability and stray inductance distribution of FDR under extreme parameters are testified.It is proved that the design can meet the system design requirement and owns high feasibility and reliability.