A multi-objective optimal design methodology for solid core no-thrust-disk/thrust hybrid magnetic bearings considering eddy-current effects and leakage

Abstract

This paper proposes a general multi-objective optimal design methodology for a new type of no-thrust-disk/thrust hybrid magnetic bearing that has been designed to reduce wind loss in centrifugal compressors. The approach dispenses with initial design results and has adjustable design objectives. To establish the proposed method we begin with its conceptual design, then look at how a parametric geometric model can facilitate manufacture, installation and cooling, before presenting a magnetic circuit model that can take into account eddy-current effects and significant magnetic leakage. The key optimization objectives selected include bearing capacity, mass, axial length, copper loss, iron loss, wind loss, and outer diameter. The approach also takes into account the performance deterioration of permanent magnets at high temperatures. By using an optimization method that combines penalty factor and selection factor, we have been able to incorporate a function for adjusting and re-adjusting the optimization goals. To verify the validity of the approach we present a concrete design case. Out of four possible schemes, a scheme based on minimum mass and axial length proves to be the best solution in this example (assuming sufficient cooling capacity).