Sizing Methodology Based on Scaling Laws for a Permanent Magnet Electrical Variable Transmission

This paper proposes a method to design an electrical variable transmission (EVT) of which the stator and inner rotor contain a distributed three-phase winding, and the outer rotor is equipped with permanent magnets and a dc-field winding. The main problem with the design of EVTs is that the modeling relies on time-consuming finite-element (FE) calculations. Studying the effect of design changes is, therefore, a cumbersome task. To minimize the need for FE calculations, scaling laws are applied, which reduce the computational effort to a matter of milliseconds per design. Therefore, the losses of multiple scaled designs can be analyzed for a given load cycle while taking constraints into account such as maximum torque. By presenting this data in a performance map, the optimal design regarding the losses is easily deduced. To validate the presented methodology, FE calculations, measurements, and available literature are used.