A novel rotor construction for reducing higher space harmonics in the permanent magnets synchronous motor

In this paper, we propose an optimal rotor construction in the permanent magnet synchronous motor (PMSM). While the field system of PMSM has generally one magnet per pole, we replace the magnet into plural submagnets for eliminating specific higher space harmonics. The dimensions and arrangements of each submagnet are derived by two kinds of methods; the one is based on the concept of pulse width modulation (PWM) and the other is that of pulse amplitude modulation (PAM). By adopting the proposed rotor construction, we can not only reduce the space harmonics of the air-gap field but also provide space for damper winding around the direct-axis. From the investigation by hybrid FE-BE (coupled finite element and boundary element) method and experiment, we present that the proposed rotor construction is effective for practical use in view of both the reduction of space harmonics and the damping effects.