Experimental Characterisation of Tilt Stabilisation within Passively Levitated Electrodynamic Thrust Self-Bearing Motors

Despite the significant advantages regarding their reliability and compactness, the interest in passively levitated self-bearing (bearingless) machines is fairly new due to the difficulty to circumvent limitations underlined by Earnshaw's theorem. Nevertheless, electrodynamic thrust bearings (EDTBs) have proved, first at the modelling and then at the experimental level, their ability to combine, within one single multifunction winding, the rotor passive axial levitation and the drive function, leading to electrodynamic thrust self-bearing (EDTSB) machines. Besides, an electromechanical model highlighted that, considering a specific connection of the armature winding, these bearings can also generate an electrodynamic torque counteracting the rotor tilt. This paper takes a step further by transposing and validating this principle and the underlying model to EDTSB machines. Consequently, self-bearing machines achieving fully passive magnetic levitation could be designed by the addition of one single permanent magnet centring bearing.