Optimal rotor construction of synchronous motor with plural permanent magnets per pole

In this paper, the authors propose a new type of rotor construction for the permanent magnet synchronous motor. By using plural permanent magnets for one-pole of the rotor, it is possible not only to reduce the space harmonics of air-gap fields but also to provide space for damper windings in the inter-pole space. The dimensions of the plural permanent magnets are derived by Fourier analysis. Based on numerical investigations, the authors propose an optimal rotor construction in view of both the reduction of space harmonics and the damping effect.