Research On The Redundant Design Of Axial Magnetic Bearing

As the application field of Active magnetic bearings is being extended, theoperation reliability of a magnetic bearing system has already become an importantindex in assessing the system performance. It is beneficial to its better application inthe fields with higher reliability requirement that improving the reliability of amagnetic bearing system. In allusion to the high reliability requirement on themagnetic bearing system, a detail research on the redundant design of an axialmagnetic bearing is carried out in this paper.Firstly, a redundant design scheme is put forward with the multi-ring structurecircle-arranged based on the full advantage of the magnetic material withoutsaturation inside. One step further, the confirmation of its structural parameters isdeduced.Then a theoretical analysis is carried out on the load bearing capacity and theadditional moment when certain failures appear in coils. Applying this onto thesix-ring structure, the redundant design principle is obtained and according to thevalue of additional moment, coil failures are divided into two categories, which arebalanced failure and unbalanced failure. Then the influence on radial magneticbearings of the additional bending moment is analysed when the additional bendingmoment is at the maximum value. Three different control strategies are proposed andcompared considering theoretical compensating current, utilization ratio of residualmagnetic poles and additional bending moment.Performance comparison from both redundancy and load bearing capacitybetween the double-ring redundant structure and the six-ring redundant structure ofaxial magnetic bearing is carried out using ANSYS. The result indicates that thesix-ring structure has advantages in both redundancy and load bearing capacity. Inaddition, the influence on magnetic field distribution of the side wall is analysed andthe magnetic force model of six-ring structure is then modified.Eventually, suspension property simulation is done using Matlab/Simulink underthe conditions of redundant reconstruction. The result indicates that the axial magneticbearing with six-ring redundant structure can realize fault-tolerant operation.