IEC 60034-9:2021

Overview

IEC 60034-9:2021 - "Rotating electrical machines - Part 9: Noise limits" specifies how to measure and limit airborne noise from standard rotating electrical machines. The standard defines test methods for sound power level (A-weighted, LWA) and sets maximum A-weighted sound power levels for factory acceptance testing of network‑supplied machines (AC or DC) of standard design, rated 1 kW up to 5 500 kW, and with rated speeds ≤ 3 750 min⁻¹. This is the 5th edition (2021), replacing the 2003 edition and its 2007 amendment.

Key topics and technical requirements

• Sound power measurement methods: procedures to determine A‑weighted sound power level independent of environment, with references to ISO/IEC acoustics methods.
• Maximum sound power limits: tabulated limits for machines at no‑load (Tables 1–3) including separate tables for 50 Hz and newly added 60 Hz machines; levels depend on rated power, cooling method (IC code per IEC 60034‑6) and protection degree (IP code per IEC 60034‑5).
• Test conditions and mounting: standardized test operating conditions and machine mounting (resilient vs. rigid) to ensure repeatable factory acceptance tests.
• Conversion to sound pressure: guidance (Clause 7) to estimate sound pressure levels at a distance using standardized measurement surfaces and indices (Annex A).
• Verification and declaration: rules for declaring sound power values and verifying compliance during factory acceptance testing.
• Converter-supplied machines: guidance on typical noise increments caused by converter supply moved to Annex B (informative); explicit exclusion of noise limits for AC motors powered by converters (see IEC 60034‑17 for application guidance).
• Notable 2021 changes:
  • Coverage extended to additional cooling methods (IC01, IC11, IC21, IC31, IC71, IC81).
  • Added Table 3 for 60 Hz machines and new grading (Grade A and B) to harmonize IEC and NEMA levels.
  • Converter noise guidance relocated to Annex B.

Applications and who uses it

• Motor and generator manufacturers - design validation and factory acceptance testing to ensure compliance with noise limits.
• Test laboratories and acoustic engineers - standard test procedures and measurement best practices.
• OEMs and end‑users (industrial plants, OEM equipment suppliers) - procurement specifications, noise control planning, and selection of machines for noise‑sensitive installations.
• Certification bodies and compliance teams - verification of declared sound power levels for regulatory or contractual requirements.

Related standards

• IEC 60034‑1 (rating & performance), IEC 60034‑5 (IP code), IEC 60034‑6 (IC code), IEC 60034‑17 (motors fed from converters)
• ISO 3741 / 3743 / 3744 / 3745 / 3746 / 3747 series - acoustics measurement methods

Keywords: IEC 60034-9, rotating electrical machines, noise limits, sound power level, A‑weighted, factory acceptance testing, IC code, IP code, converter noise, 50 Hz, 60 Hz.