A review on active magnetic bearing system limitations, risks of failure and control technologies

This paper provides a review on active magnetic bearing (AMB) system limitations, risks of failure and control technologies. Details regarding the operation of an AMB system and background on bearings and sensors are provided. The following benefits for AMBs was identified and are discussed: 1) high reliability, 2) clean environment, 3) high speed applications, 4) position and vibration control, 5) equipment design, development and testing, 6) machine diagnostics, 7) elimination of oil supply, 8) low power consumption and long life, 9) low weight and 10) capability to operate under extreme conditions. The paper further discussed the limitations of AMBs under the following headings: 1) larger bearings, 2) higher complexity and cost, 3) requires electrical power and 4) windage losses. System faults can be broadly classified as either internal or external to the magnetic bearing control system. This classification then relates to the way in which the faults can be dealt with following occurrence. The measures for reducing risks of failure include the following: 1) quality control and standards, 2) systematic check of the design, 3) software development system, and 4) redundancy. Possible future AMB control technologies are likely to be driven by 1) higher operating speeds, 2) lower power loss, 3) greater use of the available clearance, 4) generalised actuation, sensing and control and 5) control of the unbalance response, which are all discussed in this paper. The paper ends with a conclusion on the review of AMB system limitations, risks of failure and control technologie