This standard outlines a test procedure for comparing two or more insulation systems in accordance with their expected life at rated temperature. The procedure is limited to insulation systems for alternating-current electrical machines using form-wound pre-insulated stator coils and rated 6900 V and below. It is the intent of this procedure to evaluate insulation systems for use in usual service conditions with air cooling. It does not cover such special requirements as machines enclosed in gas atmospheres, subjected to strong chemicals, to metal dusts, or to submersion in liquids, etc. The procedure includes instructions for testing candidate systems in comparison with known systems having a proven record of service experience and interpretation of the results.