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IEC 60404-12:2023 is applicable to surface insulation coatings on electrical steel strip and sheet classified in IEC 60404-1-1.
This document defines the general principles and technical details of the tests for the assessment of the thermal endurance of surface insulation coatings on electrical steel strip and sheet.
The assessment is made by evaluating the change of a specified property of the surface insulation coating due to a heat treatment at a specified temperature up to 850 °C for a specified duration time up to 2 500 h. The specified property is measured at an ambient temperature of (23 ± 5) °C both without heat treatment and after heat treatment.
This edition includes the following significant technical changes with respect to the previous edition:

1. the method of test for adhesion has been modified to match to the method of bend test specified in ISO 1519 using a cylindrical mandrel of 32 mm in diameter instead of the 30 mm diameter mandrel specified in the first edition;
2. the method of test for interlaminar insulation resistance has been modified to match to the method specified in IEC 60404-11 and the modified Franklin test has been removed;
3. the method of test for compressibility has been modified to match to the method of test for stacking factor specified in IEC 60404-13;
4. the concept of "resistance grades" has been removed;
5. the clamping pressure to be used at temperature ratings above 500 °C has been reduced to (0,01 ± 0,001) N/mm2;
6. the testing for continuous exposure has been made a subject to an agreement between the manufacturer and the purchaser and the procedure has been moved to an informative Annex A.