Title: Rotordynamic analysis of machines on active magnetic bearings: comparison to fluid film bearing machines and vibration specifications

Authors: Paul E. Allaire, Timothy W. Dimond, Zongli Lin

Addresses: Department of Mechanical and Aerospace Engineering, 122 Engineer's Way, University of Virginia, Charlottesville, VA 22904-4746, USA. ' Department of Mechanical and Aerospace Engineering, 122 Engineer's Way, University of Virginia, Charlottesville, VA 22904-4746, USA. ' Charles L. Brown Department of Electrical and Computer Engineering, 351 McCormick Road, University of Virginia, Charlottesville, VA 22904-4743, USA

Abstract: This article considers rotordynamic modelling of a flexible rotor supported on active magnetic bearings (AMBs) and compares the process to a similar process for fluid film bearings (FFBs). Currently, vibration specification standards are good for industrial FFB supported rotors but are not adequate for active magnetic bearing supported rotors. This article discusses comparative studies of rotors on AMBs and FFBs involving critical speeds, AMB and FFB stiffness and damping values, mode shapes, and forced response. One objective is to assist in better communication between mechanical engineers who typically design and operate industrial machines and controls and engineers (usually electrical engineers) who design and produce AMBs. The stability of AMB machines subject to internal cross-coupled stiffness such as in seals is not considered in this work, except for the introduction.

Keywords: AMBs; active magnetic bearings; bearing-shaft stiffness ratio; closed loop damping; closed loop stiffness; critical speeds; fluid film bearings; forced response; rotating machines; vibration specifications; rotordynamic modelling; flexible rotors.

DOI: 10.1504/IJMIC.2009.027025

International Journal of Modelling, Identification and Control, 2009 Vol.7 No.1, pp.57 - 66

Published online: 13 Jul 2009 *

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