Magnetic Bearing Configurations: Theoretical and Experimental Studies

Abstract

A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because of its zero wear, negligible friction, and low cost, but it suffers from low load capacity, low radial stiffness, lack of damping, and high axial instability. To enhance the radial load and radial stiffness, and reduce the axial thrust, we have made a theoretical and experimental study of various radial configurations, including hydrodynamic lubrication to improve dynamic performance of the magnetic bearing. We developed an experimental setup to investigate the performance of bearing configurations under different operating conditions. The motion of a rotating shaft is mapped by two displacement sensors with a data acquisition system and personal computer. The first critical speed of each configuration is determined experimentally and verified through frequency analysis. We present a polar plot of displacement data.Index Terms-Hydrodynamic bearing, low-friction bearing, natural frequency of magnetic bearing, permanent-magnet bearing, wearless bearing.

Analysis of Axially Magnetized Permanent Magnet Bearing Characteristics

“…The net force acting is the bearing reactions for various positions of the rotor. In literature, analytical or semi-analytical expressions are derived and used for the purpose of calculating the bearing forces and stiffness values [15][16][17][18][19][20]. The rotor magnet is displaced from its nominal position by a distance of 'e' in XY Z coordinate system as shown in Figs.…”

“…It is proposed that the force and stiffness of the permanent magnet bearing can be increased if layers of rings are stacked with specific magnetization pattern [8]. The analytical equations for calculating the magnetic field [9][10][11][12][13][14], force and stiffness [15][16][17][18][19][20] in bearings for both axial and radial magnetization are widely available in the recent past. However in these works, the ring magnets are concentric, which might not be prevailing in actual scenario.…”

Controlling Magnetic Flux Density in Active Magnetic Bearings

“…Active magnetic bearings (AMB) are clearly favored over passive bearings [2], because they are actively controlled by means of electromagnet and results in high power loss due to the presence of a biased current, but the inclusion of suitable feedback control loops and other elements such as sensors and power amplifier makes its more preferable than passive bearing due to its lack of active control damping capabilities [3,4] Passive magnetic bearing consists of permanent magnetic placed in a position that can levitate an object in this case, the rotor making it contact free using the principles of magnetic effect [5,6].…”

Analysis of Radial Magnetized Permanent Magnet Bearing Characteristics

“…Analytical approach is faster investigation method as compared to the latter ones for the parametric study. The analytical equations for determining the magnetic field [9][10][11][12][13][14], force and stiffness [15][16][17][18][19][20][21][22] in bearings with axial, radial and perpendicular polarizations are presented by the many researchers recently. However in these works, the ring magnets are concentric, which might not be prevailing in actual scenario.…”