Insulation systems for direct-current machines are classified in accordance with their limiting temperatures as determined by test rather than by chemical composition. The intention is to classify according to the recognized A, B, F, and H categories by determining thermal capability in accordance with machine temperature-rise standards. This test procedure has been prepared to indicate accepted tests. It is applicable to insulation systems for use in usual service conditions. This standard does not cover special requirements such as for machines in gas atmospheres being subjected to strong chemicals, metal dusts, or submersion in liquids.

This section recommends an appropriate and convenient sample whereby insulating systems for small random-wound direct-current field coils may be subjected to the exposures and conditions outlined in Section to simulate and evaluate their behavior in service. It is felt that the one insulation specimen as defined in the following will adequately represent direct-current field coils as used in small integral-horsepower motors and of 600 V or less rating. Other specimens may be required to represent machines in the fractional-horsepower range as well as other than random-wound coils.

The purpose of this test procedure is to classify insulation systems for direct-current machines in accordance with their limiting temperatures as determined by test rather than by chemical composition, in accordance with IEEE Std 1-1969, General Principles for Temperature Limits in the Rating of Electric Equipment. The intention is to classify according to the recognized A, B, F, and H categories by determining thermal capability in accordance with machine temperature-rise standards. However, no standard hot-spot allowances have yet been established for direct-current machines, at least for integral-horsepower motors. These would, of course, vary with the v...