This part of ISO 14839 establishes the stability requirements of rotating machinery equipped with active magnetic bearings (AMB). It specifies a particular index to evaluate the stability margin and delineates the measurement of this index. It is applicable to industrial rotating machines operating at nominal power greater than 15 kW, and not limited by size or operational rated speed. It covers both rigid AMB rotors and flexible AMB rotors. Small-scale rotors, such as turbo molecular pumps, spindles, etc., are not addressed. This part of ISO 14839 concerns the system stability measured during normal steady-state operation in-house and/or on-site. The in-house evaluation is an absolute requirement for shipping of the equipment, while the execution of on-site evaluation depends upon mutual agreement between the purchaser and vendor. This part of ISO 14839 does not address resonance vibration appearing when passing critical speeds. The regulation of resonance vibration at critical speeds is established in ISO 10814.