Designing Of A Pyro-breaker Utilized In Superconducting Fusion Facility

Superconducting magnetic confinement fusion is considered to be an important way to solve the energy crisis.Pyro-breaker,as a backup protection switch in case of quenching,provides guarantee for the safe operation of superconducting coil due to its quick action and high reliability.As the absence of natural zero crossing phenomenon of AC circuit,the inductive DC breaking technology has always been a difficult problem in the field of switch research in the world.The Pyro-breaker in the superconducting magnetic confinement fusion device is a DC switch which is connected in series with the main circuit and driven by the explosive.It needs to have the steady state capacity of ten thousands of amperes and meet the requirements of breaking the main circuit in hundreds of microseconds in case of quenching.Compared with the common circuit breaker,the conductor system of Pyro-breaker is complex,the driving mechanism is unstable and the operation time is extreamly short.At present,the design of this kind of Pyro-breaker at home and abroad is usually based on a large number of tests to carry out relevant verification and lack of theoretical design basis.While,in the design of the conductor system,driving mechanism,water-cooling system and other parts of the Pyro-breaker,the establishment of the theoretical model can bring great convenience to the design and optimization and greatly shorten the design process.The main contents and innovations are as follows:The Pyro-breaker prototype with two-section structure,utilizing water as arc medium and with the highest parameter of 40kA/10kV has been developed for the first time in China.The prototype has been verified by experiments.All the performances meet the design requirements and the development level of Pyro-breaker for superconducting fusion device in China is improved.Based on the data fitting method,the empirical equation of contact resistance between the conductive parts of Pyro-breaker is obtained.Based on the combination of theoretical calculation and numerical simulation,the thermal electrical coupling model of Pyro-breaker conductor is established,and the thermal stability simulation is carried out.The accuracy of theoretical analysis of contact resistance and water cooling heat transfer coefficient is verified by experiments,which provides a basis for the design and optimization of the Pyro-breaker.The driving mechanism of Pyro-breaker is studied.According to the characteristics of the two-section and multi-material coupling of the Pyro-breaker,the numerical model is established,and the simulation calculation is carried out in LS-DYNA.The calculation and verification are carried out for the conductor structure,explosive dosage,driving structure,etc.Based on the results of numerical calculation,the Pyro-breaker is tested many times,and the designing of the driving mechanism of Pyro-breaker is completed.For the first time,the black box arc model is applied to such kind of underwater explosive driven breaker.A proposal of parameter selection of the black box arc model of described Pyro-breaker is proposed.The simulation is carried out in PSCAD,and the validity of parameter selection is verified by experiment,which provides a theoretical basis for the design of commutation unit of this type of Pyro-breaker.In this paper,the idea of theoretical calculation combined with experimental analysis is proposed for the desigin and development of Pyro-breaker,which simplifies the method of optimizing the switch mainly relying on a large number of experiments in the traditional design.The development level of the Pyro-breaker in the superconducting magnetic confinement fusion device in China is improved.A high voltage and high current quench protection switch solution is provided for the superconducting magnet system of next generation fusion reactor in China.