Research on Armature Thrust Inductance Gradient of the Electromagnetic Rail Launcher

The inductance gradient reflects the armature thrust in the electromagnetic rail launcher (EML). The inductance gradient is separated into two components: one is the armature thrust inductance gradient $L'_{a}$ that affects armature velocity and position and another is the rail inductance gradient $L'_{r}$ that affects the rail's forward thrust, when combined with armature inductance gradient gives the total time-varying inductive load for the pulsed power. Thus, an accurate estimate of the system current can be created, which feeds back to the armature thrust and velocity calculation. The velocity frequency $f_{v}$ is introduced to interpret the velocity skin effect (VSE). The energy storage inductance gradient $L_{u}$ varying with $f_{v}$ is obtained in the 2-D finite-element model (FEM), which is used to calculate the time-varying inductance, and $L'_{a}$ can be obtained in the 3-D FEM, which is used to calculate the armature thrust. A simulate diagram is introduced to interpret how all the system components are calculated and fit together. Launch simulations reproduce experiments to about 1%.