Analysis And Development Of Pyro-Breaker For Large Superconducting Magnet

CRAFT(Comprehensive Research Facility for Fusion Technology)is one of the major scientific devices which is built during the 13th Five-Year Plan period in my country.The superconducting magnet quench protection switch unit is one of its important subsystems,which is composed of the primary protection switch and backup protection switch.The 100 kA/10kV explosion switch developed in this dissertation is the last level protection switch of the superconducting magnet-the backup protection switch,and its importance is self-evident.In this dissertation,based on the requirements of 100 kA high current rated current carrying and 100 kA DC fast direct arc extinguishing and breaking,a new breaking principle and special structure of explosion switch are proposed,the prototype experiment and verification are carried out,which has high application value.This work firstly studies the design scheme of the backup protection switch of the superconducting magnet quench protection switch unit at home and abroad,and considers the parameter design requirements of the CRAFT superconducting magnet quench backup protection comprehensively.The design,mechanical design,electrical design,cooling system design,drive mechanism design and other aspects have been preliminary researched,designed and tested,and the design scheme of the CRAFT explosion switch is proposed.Then,based on the requirement of direct arc extinguishing and breaking of the explosion switch,the whole process of numerical simulation of dynamic breaking with arc contact is studied and analyzed for the first time.The project tested the material properties of arc contact red copper with different fracture modes,and proposed two arc contact structures with six grids and four grids for the explosion switch innovatively.Head break forming was researched,tested and optimized.The results show that the arc contacts of the two grid structures are well formed,and both can ensure the successful breaking and meet the design requirements.Then,according to the breaking characteristics of the main contact of explosion switch,the numerical simulation research and test optimization of dynamic breaking are completed.A numerical model of the main contact was established with the fracture performance of red copper material,the calculation results were analyzed and main contact was successfully broken.It is necessary to avoid major damage to the overall structure of the switch and improve the service life of switch with the main contact well formed.In addition,it is also required to ensure the timing coordination with the arc contact breaking,and the comprehensive test has been carried out.The results show that the main contact has completed the breaking and forming requirements.The overall damage and deformation of the switch is very small,and the timing sequence also meets the requirements with the same set of triggering and starting with the main contact,relying on its own structural advantages to delay arc-free breaking requirements,and achieve the design of the explosion switch.In addition,the 100 kA breaking experiment is carried out on the developed explosion switch.The mechanical and electrical properties of the designed explosion switch are verified.The results show that the developed 100 kA explosion switch can fully meet the operating requirements of CRAFT quench backup protection switch.Finally,the cooling system is also analyzed and tested,and the self-disturbing contact cooling system is proposed innovatively.The ring contact is designed as a cooling pipe as a whole,with strong convection heat transfer capability,and the overall water pressure loss of switch is relatively small to meet the requirements of 100 kA long-term steady-state flow and low temperature rise.The deformation analysis of the main and arc contacts with the condition of long-term high temperature rise is also completed.The results show that the contacts are not prone to repulsion and leakage,which meets the requirements of contact design.The 100 kA/lOkV explosion switch researched and designed in this dissertation meets the parameter requirements of large-scale superconducting magnet coil in quench backup protection switch of CRAFT,and the prototype development and test of explosion switch are completed.The test results show that the switch has high stability and breaking reliability,and meets the requirements of rapid breaking of quench backup protection switch.Many performances surpass those of traditional high-power circuit breakers.The switch can not only meet the quench protection requirements of large superconducting magnets,but also has the potential to be applied to energy storage devices,current-limiting circuit breakers,high-voltage direct current transmission and other industries.