Design, Modelling and Performance Evaluation of a Single-Phase Passively Levitated Self-Bearing Machine

Self-bearing machines have gained increasing interest by bringing the benefits of magnetic suspension to high torque density systems. Among them, passively levitated machines have recently been investigated both at the theoretical and experimental levels, but being limited to three-phase machines. For a wide range of applications, e.g. small fans, a single-phase solution would be appropriate, particularly to reduce the cost and space requirements of power and control electronics. This paper introduces a passively levitated self-bearing machine operating on a single-phase power supply. An electromechanical model describing the axial and spin dynamics of the machine is proposed, highlighting additional force and torque terms. A case study-based optimisation is then conducted to compare the performance of the single-phase solution with that of the three-phase solution, revealing that the single-phase configuration provides superior stiffness for equivalent losses, with a subsequent quasi-static analysis explaining the underlying reasons.