Speaker
Description
With ever improving performance of rare earth permanent magnet (PM) material, PM machines have been widely used. PM vernier (PMV) machines, with the working principle of flux modulation effect, have gained increasing attentions due to their high torque density. Owing to the uniformly distributed ferromagnetic poles (FMPs), the fundamental magnetomotive force induced by rotor PMs interact with both constant and fundamental term of the airgap permeance, which produce two working flux density harmonics with different pole numbers. The stator winding is designed according to the smaller pole number. In general, the higher the pole ratio (defined as ratio of rotor to stator pole number) is, the stronger the flux modulation effect will be. It has been found that through changing the FMP pitch, i.e., configuring non-uniformly distributed FMPs, additional working permeance as well as flux density harmonics can be introduced for PMV machines. These advanced PMV machine topologies can improve the torque density by more than 20%. Based on this research work, a novel spoke-type PMV machine with multi working harmonics and enhanced flux modulation effect is proposed. This machine topology is developed from a regular spoke-type PMV machine with carefully chosen slot-pole combination, i.e., 6-slot, 18-FMP, 14-rotor pole pair and 4-stator pole pair. With a low pole ratio of 3.5, the regular topology shows no obvious advantage on output torque. Nevertheless, when the FMP pitch is changed, a main working harmonic with 2-pole pair is newly produced. Hence, the stator pole pair number is changed to 2, and the pole ratio is doubled. Through FEA, it is found that the new topology can significantly increase the back-EMF and output torque by more than 60%. The field distribution, operation principle, electromagnetic performance and design issues of the proposed machine will be investigated in detail in the full paper.
| Submitters Country | China |
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