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Description
In this paper, the results of a study of the parameters which influence the efficiency of an induction coilgun are presented. Efficiency in the present context is defined as the ratio of final kinetic energy ($\frac{1}{2}$m$v^2$) of the projectile to the total input electrical energy of all the stages taken together ($\sum_{k=1}^{n} \frac{1}{2}C_{k}V_{k}^2$), where $m$ is the mass of the projectile, $v$ is the muzzle velocity of the projectile, $C_{k}$ is the capacitance used in $k^{th}$ stage, $V_{k}$ is the $k^{th}$ stage voltage and $n$ is the total number of stages. In the first part of the analysis, one of the parameters of the coilgun among the following parameters, viz., aspect ratio (length/diameter) of the projectile, inductance and resistance of the coil, capacitance and voltage of the single stage, is varied keeping all the other parameters fixed and the variation in the efficiency is studied. In the second part, the design parameters as obtained from the first part are used in the design of a multistage coilgun and it is shown that it is more efficient than a single stage coilgun and that it also gives a higher projectile velocity.
These results would be helpful for the optimal design of an induction coilgun i.e. selecting the aspect ratio of the projectile, inductance of the coil, optimum capacitance and voltage value for a constant input electrical energy. The variation in current through the coil and the rate of change of current ($\frac{di}{dt}$) are also analysed while keeping the total input energy constant and varying the stage capacitance and its charging voltage which would be beneficial for the optimum choice of the parameters of the pulsed power supply source for the induction coilgun.
