Design and Analysis of a New Parallel-Hybrid-Excited Machine With Harmonic-Shift Structure

This paper proposes a new hybrid-excited machine, termed parallel-hybrid-excited machine (PHEM) with harmonic-shift (HS) structure, or HS-PHEM. The key is to alternately place the dc-field pole pair and permanent magnet (PM) pole pair in the stator, thereby achieving the dc-field HS from the PM-field harmonics. Consequently, the dc-field harmonics interact with the PM harmonics to regulate the resultant effective harmonics in the airgap while the parallel flux paths of PM flux and dc-field flux can also be obtained, leading to more effective flux regulation ability. The operation principle and harmonics analysis are discussed, with emphasis on the validity of HS concept. Moreover, the electromagnetic performances of the proposed machine are evaluated by finite-element analysis and compared with other existing topologies in terms of torque, core loss, and efficiency. Finally, the experimental prototype is manufactured and tested for verifications.