Investigation of an axial-axial flux compound-structure permanent-magnet synchronous machine used for HEVs

An axial-axial flux compound-structure permanent-magnet synchronous machine (CS-PMSM), which is a hybrid electric vehicle (HEV) power train concept, is a structural integration of two axial flux permanent-magnet synchronous machines. It is a novel electromagnetic device with dual mechanical ports and dual electric ports. In this paper, to meet the 3D flux characteristics of the CS-PMSM, several candidate magnetic schemes for the CS-PMSM are analyzed and compared with 3D finite-element method (FEM), and an optimum tradeoff choice for the prototype machine is established. The axial magnetic force, which is unilateral and very important for the assembly, operation and choice of bearings, is evaluated using 3D FEM. A downsized prototype machine of the CS-PMSM was manufactured, but the air gaps of the machine are uneven. The effect of the uneven air gap was researched by analysis, FEM and experiments. The magnetic design and mechanical design are evaluated by experimental results.