Optimal Design of an In-Runner Direct-Drive Synchronous Permanent Magnet Starter/Generator for UAVs

The aim of improving efficiency, safety, and reliability as part of more-electric-aircraft initiatives is mediating the rapid development of aerospace systems. In addition, the increasing need for leadership in the sociomilitary-economic area brings the focus of studies on unmanned aerial vehicles in aviation. However, developments in power electronics and control algorithms, permanent magnets, high-speed transmission elements, and iron core material technologies reveal the need for using Starter/Generator structures in hybrid propulsion systems. This paper explores the optimum design of an In-runner Synchronous Permanent Magnet Starter/Generator with specifications of 1 kW-4500 rpm for motor mode and 1.25 kW-5500 rpm for generator mode, especially for small UAVs equipped with a piston engine. Thus, charging the battery packs and the required thrust can be provided with higher efficiency. The preliminary dimensions are obtained analytically. The design issues of materials and topologies are discussed. The novel model is optimised in Ansys Maxwell 2D based on finite element analyses. Dynamic and static simulations are performed with the optimetric sensitivity method, and the efficiency study is carried out in Maxwell 3D. The data obtained as a result of analytical and numerical calculations are verified.