Computationally efficient method and investigation of operational envelopes of hybrid and electrically excited machines

In this paper, an investigation on the operational envelopes of electrically excited (EE) and hybrid excitation (HE) machines for electric vehicles (EV) is highlighted. A computationally efficient calculation method utilising 2D scanning of finite element analyses (FEA) having different d- and q-axis currents is developed. Compared with the conventional method, which typically requires 3D scanning of FEA having different excitation, d- and q-axis currents, the proposed method significantly reduces the complexity and the computation time. The accuracy of the new method is validated by direct FE results. It is further found that even for EE and HE machines the maximum constant power operation in the high speed range is achieved by employing flux weakening control by the armature current instead of applying a lower excitation current, which is also validated by analytical analyses.