Passive Magnetic Levitation of Rotors on Axial Electrodynamic Bearings

The present paper presents a new modeling approach for null flux axial electrodynamic bearings. Such approach allows defining stability bounds for rotors supported with this type of passive magnetic suspension. The linearized models are developed using the bond graph methodology to better understand the multiphysics nature of the magnetic suspension. The adoption of complex variables together with the bond graph formalism is introduced in order to reduce the complexity of the system's equations. Rules for the use of this approach are established and demonstrated. The validation of the proposed models is developed comparing experimental and analytical results. To this end, a test rig, devised to achieve fully passive stable magnetic levitation, is described and used to produce the experimental data. Furthermore, experimental evidence of stable, fully passive magnetic levitation of a rotor is presented and discussed. The modeling procedure presented and validated experimentally constitutes a valuable tool for the design of magnetic suspensions including electrodynamic bearings.