Electromagnetic Analysis of an Axial Flux Air-Core Compulsator

The analysis of EML devices requires the solution of strongly coupled electrical and mechanical equations because of the fast electromechanical transient. Electromagnetic launchers are usually fed by high currents characterized by impulsive behavior. Air-core compulsators represent a promising choice for railguns. As known air cored compulsator with shields have low internal inductances and increased peak values of currents. The absence of iron and the possibility of using composite materials allow high rotation speeds. As a consequence, the energy storage ratio of the device can be increased. Further improvements could be achieved considering an axial flux air-core compulsator exploiting the superior power and energy density of axial flux electric machines w.r.t. radial flux ones. Moreover, their structure presents a planar airgap, simplifying the manufacturing aspects and enabling adjustments during the assembly phase. Axial flux devices also enable the design of multi-disk devices, stacking simple structures in the axial direction and increasing the developed torque [1], [2]. Their design inherently requires full-3D electromagnetic simulations, and consequently, their analysis is associated with intensive computational burden. Standard methods developed for more conventional radial flux iron-cored electrical machine may be not appropriate when applied to these machines. The presence of the shield complicates the identification of the parameters of the lumped equivalent circuit of the device. The strong interaction with the fed device (e.g., the railgun, excitation/control circuits) further complicates the analysis. In this study the numerical analysis an axial-flux air core compulsator is performed using a research numerical code based on an integral formulation able to consider all the principal electromechanical quantities and phenomena.