Super-multipolar permanent magnet reluctance generator designed for small-scale renewable energy generation

This paper describes a super-multipolar permanent magnet reluctance generator (PMRG) for small-scale renewable energy generation. The numbers of stator and rotor poles of the PMRG are 72 and 96 respectively, in order to be directly connected to the turbine without a gear box. The rated power of the designed PMRG is about 1.0 kW at 100 rpm. The PMRG has two features for reducing torque ripple; the first one is a two-stacked structure, namely, one rotor is shifted by 180 deg. in electrical angle from the other rotor; the second one is that the rotor pole-tips are cut off so that the torque waveform consists of only odd-harmonics. In such a structure, the torque ripple of the PMRG can be reduced drastically. In this paper, first, the shape of rotor pole-tips is optimized by two-dimensional finite element method (2D-FEM) coupled with a general purpose optimization program. Next, the load characteristics of the PMRG obtained from 3D-FEM are indicated. Finally, the measured characteristics of the developed 72/96-pole PMRG are described.