Analysis of magnetic field for inner rotor coreless permanent magnet machines with Halbach array

In this paper, the magnetic fields of a new topology motor, inner rotor coreless permanent magnet motor with a discrete Halbach array where the magnetization vector rotates 60 degree, are calculated by employing the asymptotic boundary condition technique. The flux distributions at the different radii in the effective airgap are compared when the design with and without the stator back iron. The numerical results show that the field distributions in effective airgap are not sinusoidal when the design with stator back iron. But the amplitude of flux density is larger than that without stator back iron.