In augmented electromagnetic(EM) launcher one or more pairs serial sub-rails are used to enhance the inductance gradient of rails to speed up the armature, in which the force distribution acting on rails and armature is more complicated than that in single-pair-rail EM launcher. In this paper, a numerical simulation model of interaction force between rails and accelerative force acting on armature is established based on Maxwell's electromagnetic equations and circuit equations to disclose the correlation between the force distribution and the number of sub-rails in augmented EM launcher. With same power supply, the more sub-rails pairs are used, the greater inductance gradient is and the smaller current in rails is. The simulations show at peak current the forces on rails and armature have not always been enhanced with the increase of sub-rail pairs. There is other source existed which could increase of bearing force of armature with the increase of sub-rails pares in different geometry. The simulations results also indicate that in double-layer augmented EM launcher, the sub-rails effectively enhance the armature force and magnetic flux density. However in three-layer augmented EM launcher, no obviously positive relationship between the rails layers and the bearing force of rails and armature has been found out. When the outside excitation is constant, it should be considered that the electromagnetic field is weakened with the eddy current increasing and total current decreasing.
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