Electromagnetic force analysis of a driving coil

Electromagnetic force (EMF) analysis and configuration design of a driving coil is quite important for a coil launcher. Lots of efforts have been focused on armature and control system to improve efficiency or interior ballistic characteristic. By contrast, EMF performance of a driving coil is rarely researched. The paper is intended to provide guidance for the construction and test of a driving coil. The article analyzes the EMF properties of a coil from three respects. First, EMF performances of the whole coil and its detailed construction are analyzed through three different moveable single stage coil launchers, including a whole coil and two 2-layer coaxial ring coils. Simulation results show that the whole coil with strand model is satisfied to analyze the electromagnetic performance instead of the detailed litz winding coil. In the 2-layer coaxial ring coil, EMF performances of rings are quite different from each other. Generally speaking, radial EMF concentrates to the right flank section of the whole coil, while axial EMF concentrates to the underside section of the whole coil. Radial EMF is much bigger than axial EMF. It is best to pay more attention to radial EMF which is quite useful for coil encapsulation. Then, litz coil and ribbon coil are compared by the current filament method. In terms of launch efficiency, EMF and fever, litz wire is more suitable to manufacture a driving coil than ribbon wire, although the whole progress of manufacture is a bit complicated. At last, five different models are compared to select a test model for practical situation. A static model whose armature and coil center coincide (SM2) is verified to be a simple but reasonable test model. A detailed numerical validation is presented in this paper.