Analytical Analysis of a Radial Flux Air-Cored Permanent Magnet Machine with a Double-Sided Rotor and Non-overlapping Double-layer Windings

The radial flux density in the stator region of the Radial Flux Air-cored Permanent Magnet (RFAPM) machine can be calculated analytically using the subdomain analysis method. From the analytical solution the optimum pole width of the permanent magnets, that would produce a quasi sinusoidal radial flux density distribution in the stator region, can easily be calculated. The requirement for a sinusoidal radial flux density distribution in the stator region, is that it allows for a voltage - and torque constant to be defined for the RFAPM machine. This not only simplifies the design procedure in terms of sizing the RFAPM machine, but also simplifies the control aspects of the RFAPM machine. Furthermore, the torque developed by a RFAPM machine, specifically with regard to the size and shape of the ripple torque is also calculated analytically using the Lorentz method. All the analytical results are bench-marked against Finite Element Modelling (FEM).