ISO 14839-3:2006

Overview

ISO 14839-3:2006 - Mechanical vibration: Vibration of rotating machinery equipped with active magnetic bearings (AMB) - Part 3: Evaluation of stability margin - defines how to evaluate the stability robustness of rotating machines that use active magnetic bearings. The standard applies to industrial rotating machinery with nominal power greater than 15 kW (no limit on size or rated speed), and covers both rigid and flexible AMB rotors during normal steady‑state operation. It specifies a stability index, measurement procedures and evaluation criteria to quantify the stability margin required for safe, reliable AMB operation.

Key Topics

• Scope and applicability
  • Targets industrial rotating machinery with AMBs; excludes small-scale rotors (e.g., turbomolecular pumps, spindles).
  • In‑house evaluation is required prior to shipping; on‑site testing is by agreement.
• Stability index and measurement
  • Defines a specific index for evaluating stability margin and the method to measure it (open‑loop/closed‑loop transfer functions).
  • Measurement methods use two‑channel FFT analysis and injection of excitation to derive open‑loop G_o(jω) and closed‑loop G_c(jω).
• Control and system characterization
  • Describes AMB feedback architecture (typically multi‑axis control - e.g., five axes) and the relationship between plant and controller transfer functions.
• Analysis tools and criteria
  • Uses industry standard robustness measures such as gain margin, phase margin, Nyquist plots, and the sensitivity function (1 / [1 + G_o(jω)]).
  • Emphasizes the minimum distance of the Nyquist locus to the critical point (−1,0) and maximum sensitivity as conservative stability indicators.
• Preceding investigations
  • Differentiates run‑up/Q‑factor (resonance) evaluations - covered by ISO 10814 - from steady‑state control stability covered here.
• Supporting material
  • Annexes include case studies, field data and analytical examples to guide measurement and evaluation.

Applications

Who uses ISO 14839-3:

• AMB system vendors and OEMs for design verification and shipping acceptance testing.
• Test and commissioning engineers performing in‑house or on‑site stability assessments.
• Mechanical and control engineers specifying robustness margins in contracts and maintenance procedures. Practical uses:
• Contractual acceptance criteria for AMB‑equipped rotating machinery
• Commissioning checklists and performance reports
• Diagnostic baseline for maintenance and troubleshooting of AMB control loops

Related Standards

• ISO 14839-1: Vocabulary (part of the same series)
• ISO 14839-2: Evaluation of vibration (related AMB vibration assessment)
• ISO 10814: Regulation of resonance vibration and Q‑factor requirements during run‑up and critical speed passage

Keywords: ISO 14839-3, active magnetic bearings, AMB, stability margin, Nyquist plot, sensitivity function, gain margin, phase margin, rotating machinery, vibration standards.