The eddy current braking machines have the advantages of no liquid leakage,no sealing required,and stable resistance.Compared with the more widely used permanent magnet eddy current braking machine,hybrid excitation eddy current braking machine replaces part of the permanent magnet with a coil an achieves better resistance characteristics.In this paper,two possible structure of hybrid excitation eddy current braking machines was compared.Based on magnetic circuit analysis and preliminary calculations,the structure with better resistance performance was selected.Equivalent magnetic circuit method was utilized to calculate the air gap magnetic field and subdomain models were adopted to consider effects of induced eddy current.Then,an equivalent subdomain model was established for calculating the resistance value of hybrid excitation eddy current braking machines.According to the requirements of a certain caliber artillery recoil,the main dimensional parameters of the braking machine were determined,and the preliminary design of the structural parameters of hybrid excitation eddy current braking machines was obtained.The analytical calculation results were verified by numerical calculation.Based on the working conditions when a certain caliber artillery is fired,the chamber force curve and recoil stroke function curve of complex feed mechanism were adopted as input conditions.A simulation model was established to analyze the electromagnetic damping force,recoil displacement and recoil velocity of hybrid excitation eddy current braking machine under strong impact load.Finally,the influence of different air gap widths and inner cylinder conductivity on electromagnetic damping force is analyzed.The results show that the smaller the air gap width is,the larger the electromagnetic damping force is.Meanwhile,higher conductivity of the inner cylinder will lead to the electromagnetic damping force showing a"saddle"type.The research provides a theoretical basis for the engineering application of the hybrid excitation-type eddy-current braking machine.
hybrid excitationeddy current braking machineequivalent magnetic circuit methodsubdomain modelelectromagnetic damping force
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