Dr Liangbing HU (Institute of Plasma Physics, Chinese Academy of Sciences)Dr Zhiwei Zhou (Institute of Plasma Physics, Chinese Academy of Sciences)
A 500W@4.5K helium refrigerator has been designed to provide forced flow cooling of 4.5K supercritical helium for the superconducting coils testing or as a helium liquefier with the capacity of 90L/hr liquefaction rate, and is now in built at the Institute of Plasma Physics, Chinese Academy of Sciences (CASIPP). Its control system is designed and developed based on a Programmable Logic Controller (PLC) to achieve automatic process control in each defined operational mode. Via the analysis of process flow and control requirements, all operational modes with their logic control such as start-up conditions and interlocks have been designed. Through the process modeling and dynamic simulation, the dynamic behaviors of cryogenic process were revealed and the process parameters control loops were designed and simulated for optimizing the cool-down operation. As the core machinery in the refrigerator, two turbines with fully static gas bearing in series, which adopted double-valve fan brake control loops for optimized rotation speed control, are designed and manufactured by ourselves and will be tested in the commissioning of the refrigerator. In this paper, the design of automatic control strategies for the refrigerator as well as its control programs development and application on PLC control system will be presented in detail. Also, the whole project progress of the refrigerator and its control system will be reported.
Dr Zhiwei Zhou (Institute of Plasma Physics, Chinese Academy of Sciences)