Hybrid excitation permanent magnet synchronous machines and their structures — Combination art of elements of machines

Hybrid excitation permanent magnet machines (HEPMM) combines two kinds of excitation: permanent magnet (PM) and electrical excitation, to keep the advantages of PM machines and overcome the difficulty in regulating magnetic field at the same time. By now there are so many HEPMM schemes with different structure and principle have been presented that it is difficult for successors to follow and catch the outline. In order to summarize the characteristic of magnetic circuit of different HEPMMs, this paper proposes one novel classification method based on the position relationship of PM poles and iron poles. The PM poles and iron poles are essential and inevitable for HEPMMs, and their position relationship gives a clear clue to the characteristic of magnetic circuit and is easy to understand. In addition, the main objects, difficulties and considerations of HEPMMs are given. The considerations of field winding, shape and position, are discussed, which relate to the excitation loss and reliability. More than 50 papers and patents worldwide are referred in this paper.