Vibration Criteria Considered from Case Studies of ActiveMagnetic Bearing Equipped Rotating Machines

The main part of turbo machinery is conventionally supported by oil film lubricated bearings.The rotor vibrations can be suppressed within low levels as to satisfy vibration criteria, e.g.,ISO standards for general rotors and API 617 for process compressors. Recently, thesophisticated advantages of the active magnetic bearing (AMB) have been increasing thenumber of applications to industrial rotors. The AMB vibration control design requiresthe weak support which induces inevitably large vibration amplitude, though it is normal forAMB itself. Vibration criteria indicated by present standards are thus too strict for AMBequipped rotors. The difference of the bearing dynamic characteristics between the oil filmlubricated bearing and the AMB compels us to prepare a new ISO standard whichrecommends the acceptance of higher vibration levels for AMB operation