Design procedure and optimisation methodology of permanent magnet synchronous machines with direct slot cooling for aviation electrification

Electric machines are widely employed in a variety of sectors, including automotive and aerospace industry. With the rising trend towards electrification in aviation, electric machines with increased power density and efficiency are becoming key enabling technologies, requiring the development of innovative design procedures. In this study, a preliminary design procedure for Surface Mounted Permanent Magnet Synchronous Machines (SPMSMs) intensively cooled by means of oil channels placed in the stator slots is proposed. The analytical derivation of SPMSM sizing equations, including the sub-domain model and optimisation algorithm will be reported in detail. Indeed, both the electromagnetic and thermal equations of the machine are considered for the derivation of the sizing tool. As a result, the latter allows to capture variation of the machine design not only in terms of mechanical demands, such as power and speed, but also in terms of coolant characteristics, and can be effectively employed to perform trade-off studies at a preliminary design stage. The proposed design tool will be used for a specific case study: The design of a high-speed machine for an aerospace hydraulic actuator. The accuracy of the proposed design tool is validated for different parameters by comparing the results to experimental measurements performed on an existing 8-pole 9-slot prototype SPMSM.