Hybrid excited claw pole rotor for high power density automotive alternators

This paper presents and investigates an improved 3D-excited hybrid claw pole alternator. The new alternator design is achieved by adding two axial PM rotor components on the lateral sides of the main claw-pole rotor. These additional rotor components are located under the endturn regions of the stator winding. Therefore, the complete machine space including the end-winding region can be utilized to boost the rotor flux, thus to achieve higher alternator power density and efficiency. A validation of the new claw-pole alternator concept has been performed with 3D finite elements. Several simulations are made in order to estimate the boosting effect at different load conditions and with different magnet materials for the lateral rotors. The new rotor with ferrite magnets boost the rotor flux for 2 times, while the NdFeB rotor for 2.8 times. Moreover, the analyses also prove the self-weakening effect of the proposed hybrid rotor. Hence the stator iron losses due to magnets at no load are minimal. Finally, the results of an mechanical comparison indicate that the new construction improves also the structural rigidity of the CPA rotor.