Effect of an Armature Winding Misalignment on Passively Levitated Self-Bearing Machines

Passively levitated self-bearing machines provide the rotor drive and guidance within a single structure without requiring controllers, power electronics and sensors dedicated to the magnetic suspension, leading to compact, reliable and cost-effective systems. Electromechanical models describing their rotor dynamics have recently been derived and experimentally validated. However, these models do not account for non-idealities that could arise from manufacturing imperfections. In this context, this paper investigates the impact of an angular misalignment between the upper and lower windings of passively levitated self-bearing machines on the force and torque production. The existing electromechanical model is extended, highlighting that this misalignment slightly degrades the driving torque and the conventional passive restoring force, on the one hand, and creates additional force and torque components, on the other hand. Among the latter, those arising from the suspension currents are independent from the rotor axial displacement and are thus produced even in centred position, thereby potentially acting as disturbances. Finally, an experimental study is carried out, allowing to validate the suspension force produced by the machine in quasi-static conditions and to confirm the interest of accounting for this winding non-ideality in the model.