Stability of an electrodynamic suspension

Abstract

Previously, the authors have described a method of dynamically stabilized noncontact electromagnetic suspension of rotating bodies. The method makes use of the dynamic interaction between stationary and rotating sets of conductors and permanent magnets. The validity of this method has been demonstrated by building and testing a prototype in which noncontact suspension of a 3.2 kg rotor was achieved when it rotates at speeds above 18 Hz. A stability condition for that method of suspension was obtained with certain simplifying assumptions. One of these assumptions was that the inductive component of the stationary conductors is negligible. Here, we present modified stability conditions which take the inductance of the stationary conductors into consideration. One of the predicted effects is that nonzero inductance may cause significant reduction of the minimum stable levitation speed. Consequently, careful choice of the electrical properties of the stationary coils may significantly enhance the performance of the suspension.

Unified modelling of passive homopolar and heteropolar electrodynamic bearings

“…(10) and (11) describe the magnetic flux linkage perceived by the rotor, and Eqs. (13) and (14) give the force acting on the rotor.…”

“…A discussion about the influence of the electrical parameters of the rotating conductor has been initiated, and stability issues have been explored more deeply [13]. The continued difficulty of ensuring whirl stability has been addressed [14], and finite element analysis has been used to quantify the parameters of the bearing that affect its stability [15].…”

Null-Flux Coils in Permanent Magnets Bearings

“…For example, devices characterized by the presence of time-varying fields (e.g. eddy currents in alternating magnetic fields [8]- [13]) could not be affected by the instability problem. Other devices can be envisaged considering proper arrangements of PMs which are kept in motion nearby conductive domains.…”

A Novel Flexible PCB Conductive Structure for Electrodynamic Bearings and Measurement in its Induced Voltage

“…In the previous researches, the cylinder conductors and short-circuits coils were commonly used in the conductor configuration in EDBs [1,[9][10][11][12][13][14]. However, it is not sufficient for them to meet the above requirements.…”

“…The earliest application of electrodynamic bearings dates back to the 1980s and 1990s -used for flywheels [3][4][5][6][7][8][9][10][11][12][13][14][15] because electrodynamic bearings' features matched flywheels' requirements very well. Firstly, flywheels typically work at the state of high-speed rotation, and it is at such high rotation speed that electrodynamic bearings can realize levitation; secondly, stiffness and rotation precision are not core requirements of flywheels, which are also drawbacks of electrodynamic bearings.…”