IEC 60172:2020

Overview

IEC 60172:2020 - Test procedure for the determination of the temperature index of enamelled and tape‑wrapped winding wires - specifies a standardized method to evaluate the thermal capability of winding wire insulation. Aligned with IEC 60216‑1, the procedure exposes specimens to controlled heat‑storage cycles in air at atmospheric pressure and periodically applies AC proof voltage tests to monitor insulation deterioration. The temperature index (TI) is the Celsius temperature corresponding to an extrapolated lifetime of 20 000 hours on an Arrhenius thermal‑endurance plot.

Key topics and requirements

• Scope and exclusions: Applies to enamelled wire (varnished or unvarnished, with or without impregnation) and tape‑wrapped round/rectangular wire. Does not apply to fibre‑insulated wire or tapes containing inorganic fibres.
• Specimen preparation: Detailed methods for enamelled non‑tape wrapped round wire (nominal conductor diameters from 0.224 mm up to 2.65 mm) and for tape‑wrapped round/rectangular wire are specified to ensure repeatable results.
• Test cycle: Repeated heat‑storage exposure at selected temperatures followed by room‑temperature AC proof voltage tests until sufficient specimen failures occur.
• Data analysis: Calculation of specimen failure time, time‑to‑failure statistics, linear regression of log(life) versus reciprocal absolute temperature, and plotting on thermal endurance graph paper to derive TI.
• Reporting: Test report must include results and statistical metrics - Clause 9 now requires inclusion of the correlation coefficient (r) for the regression.
• Normative references: IEC 60216‑1 (ageing procedures/evaluation) and IEC 60216‑3 (calculating thermal endurance characteristics).

Applications and who uses it

• Winding wire manufacturers use IEC 60172 to characterize enamel and tape insulation and to support product datasheets (temperature index, thermal class guidance).
• Motor, transformer and generator designers rely on TI data to select appropriate winding wire for insulation systems and for further equipment qualification tests.
• R&D and materials engineers use the method to compare insulation formulations, varnish impregnation effects, or tape systems under accelerated thermal ageing.
• Test laboratories and certification bodies apply this standardized procedure to provide reproducible, comparable thermal‑endurance data.

Practical value

• Provides a reproducible, internationally recognized method to quantify insulation thermal performance.
• TI data support material selection, comparative evaluations, and risk‑based design decisions for electrical rotating machines and other wound components.
• Inclusion of statistical metrics (e.g., correlation coefficient r) increases confidence in TI extrapolations and design use.

Related standards

• IEC 60216‑1 - Electrical insulating materials: Thermal endurance procedures and evaluation.
• IEC 60216‑3 - Instructions for calculating thermal endurance characteristics.

Keywords: IEC 60172, temperature index, enamelled winding wire, tape wrapped winding wire, thermal endurance, AC proof voltage, winding wire testing, IEC 60216.