Description:
Background
Magnetic bearings are commonly used in many rotating machines, such as pumps, compressors and turbines. In such machines, a five-axis, active magnetic bearing configuration is frequently employed; this configuration must maintain power to electromagnets for each of the five axes. In this arrangement, one axial active magnetic thrust bearing acts upon a thrust disk that is attached to a rotor in order to control axial rotor vibrations, while two radial active magnetic bearings act upon the rotor in two directions to control radial vibrations.
While this configuration is useful, it suffers from shortcomings such as high power losses and requires a thrust disk or radial thrust forces, either of which may interfere with fluid flow through the rotating machine.
Invention Description
Scientists at the University of Virginia have developed an integrated, hybrid, five-axis passive and active magnetic bearing system and related method. This technology is designed to suspend a rotor within a non-rotating stator without the use of conventional rolling elements or fluid film bearings.
With this innovative technique, the rotor is axially centered in the stator using an axial-permanent magnetic set of poles, where the axial-repulsive forces generated keep the rotor centered without using a thrust disk or radial thrust forces. The rotor is centered radially using radial electromagnetic bearings. A combined axial-/radial-permanent magnet bias flux path provides a bias flux for the radial bearings. Reverse polarity magnets placed in the stator create high axial magnetic centering forces and high permanent magnetic bias flux levels for the radial bearings, offering distinct advantages over using single-polarity magnets in the stator.
Advantages
This invention offers several advantages over conventional magnetic bearing designs, including:
- An extremely compact and energy-efficient design, with minimum electric power consumption in the radial bearings
- Absence of radial thrust forces or a thrust disk on the rotor
- Reverse-polarity magnets that are incorporated to allow for a much higher force capability in both axial and radial bearings
Applications
While this technology can be applied to any kind of rotating machine, it is of particular interest in blood pumps, where the absence of a thrust disk will prevent low blood-flow areas and thus significantly lower the risk of blood clotting.
