Simulation And Basic Experiments Of Contactless Power Transfer For Superconducting Magnet Based On Magnetic Coupling Induction

Presently,the main charging method for superconducting magnets is utilizing the external driving power source.Because power circuit needs to undergo the temperature changes from room temperature to extreme low temperature for superconductor,the heat leakage and loss generated by current leads will reduce the cooling efficiency of the cryogenic system.It can easily lead to the quench of the superconducting magnets and cause irreversible damage.On the other hand,the research and application of the contactless power method,which is the most ideal in such low temperature environment,is scarce.Based on this background,a contactless power supply system for high temperature superconducting(HTS)magnets is proposed in this paper,which has been analyzed and optimized by circuit principle analysis.This method combines the designed structure of contactless power coupler and cryogenic rectifier,to replaces the current leads adopted in the traditional power system which needs to undergo the temperature changes from atmospheric environment to liquid nitrogen temperature,to power for the HTS magnets.Considering the difference between HTS magnet and general load,two different contactless power coupler circuit topologies are compared and analyzed in this paper.From the comparison results of electrical characteristics of these two different structures,the circuit topology which is more suitable for small load resistance,large load current and liquid nitrogen environment is selected.According to the established equivalent circuit model,the charging characteristics of the circuit and the influence of various parameters on the system are analyzed in detail,and the design concept of the system is put forward.Rectifier circuit in cryogenic environment is particularly significant for the system proposed in this paper.In order to investigate the working performance in the liquid nitrogen and design the reasonable rectifier circuit,low temperature experiments for the different types of diodes manufactured by different commercial suppliers are carried out.The diode for the optimal performances is selected from the test result,which is used to constitute the rectifier operating in the liquid nitrogen.Combining with the contactless coupler part and designing the circuit parameters based on the optimization algorithm,the scheme design of the whole contactless power supply system is completed.In addition,the experimental prototype based on the design scheme is also developed in this paper,and the feasibility of the system is verified by the basic tests in liquid nitrogen.In the experiments,the air gap between the both sides of the contactless coupler ranges from 30 mm to 100 mm,which provides enough space for the future research to design the cooling system of HTS magnets.Under the cooperation of contactless power technology and cryogenic rectifiers composed by high-speed diodes,the system successfully charged the HTS magnets with a maximum current up to 37 A.The experimental results have good agreements with analytical calculations,which provides the theoretical tool and basic experimental condition for improving the system performance.