Analytical Electromagnetic Sizing of Inner Rotor Brushless PM Machines Based on Split Ratio Optimization

Paper in proceeding, 2018

This paper presents an analytical procedure to size brushless PM Machines from a set of required performance specifications. The sizing is obtained by optimizing the machine's split ratio, defined as the ratio of the stator inner to outer diameter. This ratio is key in the design of the machine and it is a compromise among several performance factors, and in particular it is shown to be a trade-off between efficiency and torque density. The split ratio also affects the volume of each material and in turn the cost of the machine. The algorithm outputs the machine performance and cost curves as a function of the split ratio, giving the possibility to the user to decide the best compromise for a certain application. The analytical sizing procedure is built and integrated with a 2D FEM simulator for refinement and verification of the design. A case study is presented and validated to prove the effectiveness of the sizing procedure.