Design Of Superconducting Magnetic Field Power Supply For Single Crystal Furnace

In order to improve the quality of silicon single crystal used in the large scale integrated circuit,it is necessary to control the convective morphology of the silicon solution in the single crystal furnace.To apply the strong magnetic field outside the furnace body is an effective way.With the development of superconducting technology,superconducting magnet has been widely applied in the field of high quality silicon single crystal growth.Superconducting magnet has the advantages of small volume,low power consumption and high magnetic field strength.Due to its high magnetic field strength,the slight fluctuation of the excitation current in the magnets will also cause a large change in the magnetic field intensity,which destroys the steady state of the crystal growth and affects the crystal quality.Therefore,in order to produce high quality silicon single crystal,superconducting magnet has higher requirements for the accuracy,stability and reliability of excitation power supply.The excitation power source of superconducting magnets belongs to the application of low voltage and large current.In this paper,the BUCK circuit is chosen as the main topology of excitation,and the state averaging method is used to model the BUCK converter with inductive load.A fuzzy sliding mode controller with an incremental switching term is designed.The controller adjusts the switching coefficient in the sliding mode control by fuzzy control to reduce the chattering and guarantee the stability of the system.The stability error of the traditional sliding mode controller is overcome and the sensitivity of the system to noise is reduced by an incremental switching term.SIMULINK is used to simulate and compare traditional and improved control algorithms.The simulation results show that the fuzzy sliding mode controller with incremental switching term is better than the traditional fuzzy sliding mode controller for the inductive load BUCK converter.The driving circuit and protection circuit of the main power device are designed.The improved control algorithm is used to control the prototype of the superconducting magnet power supply.The experimental results prove the effectiveness of the control method.Finally,the bridge detection method for superconducting magnets is studied and discussed.At the same time,the MATLAB is used to simulate the quench process of superconducting magnets.