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To obtain high velocity and high energy conversion efficiency on a synchronous induction coilgun, the armature capture effect which is the inherent characteristic for the synchronous induction coilgun needs to be analyzed. The reason for the armature capture effect is first deduced and analyzed using the lumped element circuit model and then quantificational result is obtained based on the field-circuit coupled model. According to the analytical result, the method to minimize the armature capture effect is proposed from the viewpoint of the magnetic coupling between the driving coil and the armature. Several ways are analyzed through the finite-element simulation. The simulation results show that adjusting the power parameters, such as increasing the capacitance or initial voltage, and decreasing the crowbar resistance, and adjusting the armature parameters, such as decreasing the mass or adopting the solenoid armature, can minimize the armature capture effect and increase the conversion efficiency. These methods are validated through a four-stage induction coilgun. We compare the simulation results with the experimental results and show that by adjusting the armature parameters, we can minimize the armature capture effect. It provides valuable reference for synchronous induction coilgun design. [ABSTRACT FROM PUBLISHER]

Driving coils in a multistage induction coilgun are stacked end to end forming a barrel. During launching, the pulsed current flows through the driving coil, and the electromagnetic force propels the projectile ahead. The driving coil endures not only the radial expansionary force because of the magnetic flux compression, but also the axial force due to the compressive force and counterforce of the projectile. In the process of coil design, both the mechanical strength and the electrical insulation must be considered. Due to the nonlinearity of insulation materials, the theoretical calculation cannot reflect the true state for the driving coil. The conventional static-state test method is analyzed and verified through experiments. The experimental results show that this method is ineffective for the multistage launching, because it neglects the axial counterforce and does not reflect the true state of launching. An improved method for evaluating the coil strength is proposed based on the analysis of the basic principle. The projectile is accelerated by the former stages, and the testing coil accelerates the projectile with an initial speed. Equipment for testing single coil is designed and installed in the muzzle of the existing multistage coilgun. The experimental results show that this method can test the coil’s mechanical strength and electrical insulation more effectively than the conventional method. The dynamic-state method can be used to approximately evaluate the performance of different types of the coil. The structure of the driving coil can be improved through testing and evaluating, which provides experimental reference for the multistage induction coilgun design. [ABSTRACT FROM PUBLISHER]

Based on understanding the characteristics of the impulse force generated by pulsed current of the armature, it is valuable to explore effective ways to improve the armature structure to enhance the stability and prevent from the transition and erosion during launching. This paper first lists a series of conversional armature and the characteristics of these armatures are illuminated. A C-shaped armature is simulated based on the electrical–magnetic–mechanical coupled analysis method. The simulation shows that the stress is mainly distributed in the area between the cross member and arm, it may lead to local deformation. A novel concave armature is proposed and the simulation results indicate that the stress is mainly distributed in the inner side of arm and the front of armature. It is beneficial to push heavy load and avoid deformation and fracture. A device is built to validate the feasibility of armature. The armature is staying still to simulate pushing the infinite heavy load. The experimental results show that the concave armature endures higher current and has the stronger capability of pushing load compared with the C-shaped armature. This type of armature provides a valuable reference for future armature design. [ABSTRACT FROM PUBLISHER]

A large muzzle kinetic energy railgun is developed to demonstrate the supersonic launch of 200 mm projectiles. A trade is studied that evaluates over 30 different railgun cases resulted in the selection of a simple railgun as the choice. The goal of the railgun launches a 200 mm diameter projectile with a mass of greater 20 kg to a velocity of 2500 m/s, and the muzzle kinetic energy is more than 62 MJ. The analysis and modeling of the electromagnetic launch results in an adequate design. The final railgun is designed with an 8 m barrel and characterized by the following parameters: conducting rails with an inductance gradient about 0.4 \muH/m, a peak current of about 7 MA, an effective current of no <6~MA, the projectile muzzle velocity of 2540 m/s, the muzzle kinetic energy of more than 63 MJ, and the system efficiency of 31.8%. A more detailed study is presented in this paper. [ABSTRACT FROM PUBLISHER]

To demonstrate the multistage induction launch capability and test the accuracy of the simulation result, a small-scale, 4-stage synchronous induction coilgun is designed, fabricated, and tested based on the simulation result. The four coils are stacked end-to-end, forming a barrel, and each coil is energized by the identical pulsed power supply in sequence to create a traveling magnetic wave that accelerates a projectile. The inductance of four coils is tailored by changing the number of turns in order to decrease the pulsed current risetime. The tracking of the projectile location during a launching provides a precise feedback to control when the coils are triggered to create the wave. Two types of the projectiles are tested. A 0.65-kg sleeve projectile is accelerated from rest to 125 m/s with a projectile kinetic energy to capacitor-stored energy efficiency of 6%. A 1-kilogram sleeve projectile is accelerated from rest to 92 m/s with the efficiency of 5%. The solenoid projectile is broken at the bending point when it induces high current. The launcher provides data for model verification and the engineering basis for proceeding with larger multistage system. Further research is to improve the system efficiency and maximize the magnetic coupling between the driving coil and the projectile. [ABSTRACT FROM PUBLISHER]

An improved large-caliber synchronous induction coilgun is designed and tested to demonstrate the launch of 120-mm projectiles. This induction coilgun consists of 15 identical coils forming a long uniform barrel for simple design and fabrication. Fifteen separate coils are fit in a long insulative tube and molded once with elastic insulative material that isolates the coils with the containment. The 15-stage induction coilgun provides a significant improvement in the armature capture effect, system efficiency, and coil structure. A computer simulation model based on the viewpoint of finite element analysis software is developed to predict the performance of the launcher system. Five-kg copper projectiles are accelerated from rest to 220 m/s through the 2.5-m launcher assembly with a projectile kinetic energy to capacitor stored energy efficiency of 14.5%. Further experimental studies are continued. [ABSTRACT FROM PUBLISHER]