Equivalent Network Modeling of a Coreless Electromagnetic Launcher

Coreless ElectroMagnetic Launchers (EMLs) operate at high-power levels and in transient regimes involving strongly coupled electrical and mechanical aspects. The absence of ferromagnetic materials eliminates the rise of the cogging force and hysteresis losses, which are typical of iron-core devices. Moreover, considering EMLs equipped with Permanent Magnets (PMs), it is possible to conceive devices with high efficiency, force density, and improved performance. Adopting a distributed winding configuration on the stator, it is possible to obtain a sinusoidal airgap magnetic flux density created by the stator coils, avoiding the presence of high-order spatial harmonics interacting with the moving PMs. In this way, the minimization of the windings and PM losses can be achieved. Most studies of these devices, however, rely on the solution of extensively simplified analytical models and 2D Finite Element (FE) simulations, which cannot address all the aspects involved in a coreless linear launcher. In particular, these simplifications neglect the presence of 3D leakage flux paths, which can strongly affect their performance [1-3]. In this contribution, a coreless PM electromagnetic launcher is analyzed using the research code “EN4EM”. This code is based on the integral 3D formulation of the magnetic diffusion equations, which reduces the electromagnetic field analysis to an equivalent network solution [4]. This approach involves discretizing only the active parts, such as conductors and magnetic materials (i.e., the back iron), reducing the size of the resulting solution matrices. Although these matrices are typically dense, leading to increased computational effort, reasonably accurate results can be achieved using a relatively coarse discretization. However, applying this approach simplifies the analysis of systems that include external lumped circuits (e.g., pulse-forming networks) or sliding contacts since the coupling is straightforward. In particular, an extensive analysis of the electromagnetic behavior of this device is performed, considering full-3D transient simulations with up to 6 Degrees of Freedom (DoF) [5] to analyze the transverse components of the motion.