Here, different feasible configurations of passive permanent magnet bearings (PMBs) are presented and compared with each other. In these configurations, stiffness is improved by adding iron cores and air intervals between magnets. Bearings with opposite magnetisation stacking (standard) and rotating magnetisation stacking (Halbach) are studied here. A twodimensional planner model is used to calculate the magnetic field and stiffness. The optimisation will be performed for obtaining maximum stiffness per magnet volume ratio. The results show that standard stacking with radially magnetised PMs and having back iron and air intervals between magnets is the most optimum structure. For larger dimensions of magnets, other structures will be useful too.
Passive magnetic bearings offer significant advantages relative to common active magnetic bearings, such as simple, robust, and efficient structure. Permanent magnet (PM) passive magnetic bearings are composed of opposing magnet rings on rotor and stator. Although their stiffness has been improved using alternating or Halbach magnetisations in many previous studies, they still suffer from lack of damping force. In this study, the optimal design is focused on a combination of PM bearing and eddy current damper by adding a conductive layer along the magnets of the stator or rotor. This will moderate the magnetic material consumptions; thereby, the cost and overall size of the bearing are reduced. A complete analytical method is performed to calculate the stiffness and axial, radial, and rotating damping coefficients. The accuracy of the analytical model is estimated quantitatively using 3D finite element method simulations. Moreover, all of the parameters are normalised and optimised for maximum stiffness and damping. ξ Fourier transforms parameter ω rotational speed
Purpose
This paper aims to suggest the use of air or iron intervals between axially magnetized rings to increase the forces and stiffness of permanent magnet passive magnetic bearings (PMBs). The paper calculates the stiffness of such bearings through an analytical method and optimizes the dimensions of the magnets for achieving maximum stiffness.
Design/methodology/approach
For determining the magnetic fields distribution, forces and stiffness of the bearings, a 2D analytical method is used, based on the subdomain method. For the sake of generalization, all of the parameters are normalized and optimized for maximum normalized stiffness per magnet volume ratio.
Findings
The optimum sizes of the magnets as well as the optimum dimensions of the air or iron intervals are calculated in this paper. The optimum sizes of the magnets are around the air gap length and it is very difficult to realize them. Using iron intervals can improve the stiffness to the extremely high values in practical dimensions of the magnets.
Originality/value
This paper presents a novel configuration for improving the performance of PMBs with alternately axially magnetized rings.
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