04-08-2012, 12:21 PM
Working principle of active magnetic bearing
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The magnetic bearing works just like normal mechanical bearing except the bearing functionality is achieved utilizing magnetic field. In magnetic bearing system the rotor is levitated in the magnetic field. The magnetic bearing system can be either of two types:
(i) Active magnetic bearing in which all are electromagnets and
(ii) Passive magnetic bearing in which a combination of electromagnets and permanent magnets (PM) are used.
Recently, Active Magnetic Bearings (AMBs) have gained much attention in the rotating machinery field. They offer several advantages over conventional bearings (i.e. roller and fluid film bearings). These advantages include low power loss, elimination of lubricant systems, no contact during normal condition operation and the ability to control the bearing forces to reduce vibration 1. Most common applications include Turbo-machinery, electric motors, vacuum technology and Machine tools. AMBs require the feedback control of magnetic forces to ensure stability on the magnetic suspension.
EXPERIMENTAL SET-UP
presents the experimental set-up to be identified. The speed-controlled dc motor drives a shaft (diameter 9.5 mm, length 30.5 mm.), supported at one end by a magnetic bearing and at the other (the one closest to the dc motor) by a conventional ball bearing. An inertia disk is mounted on the shaft, and load unbalance can be included by adding masses to the disk. Basic position sensor sensitivity is 100μm/v. The rotor pivots on the ball bearing, thus isolating the dynamics of the AMB.