Ironless permanent magnet motors: Three-dimensional analytical calculation

We present a three-dimensional expression of the magnetic torque exerted between a tile permanent magnet radially magnetized and a winding in ironless structures. Such an expression can be used for calculating the magnetic torque transmitted between the stator and the rotor of an ironless permanent magnet motor. The calculations are carried out without using any simplifying assumptions. Consequently, the expression of the torque obtained is exact whatever the magnet or winding dimensions. The ironless structure we consider in this paper is commonly used for high speed rotation devices in which eddy currents must be avoided. Indeed, it is noted that more and more structures are ironless because they offer promising perspectives.