Principles for temperature classification of insulating materials

The present AIEE Standard No. 1 - “General Principle upon which Temperature Limits are Based in the Rating of Electric Machines and Apparatus” - was first introduced about 1913. This standard has provided a firm basis for many years despite the arbitrary way in which materials are defined by their chemical composition. In recent years many new insulating materials have become available. The problems associated with classifying these newer materials such as the silicones in the classes as defined in AIEE Standard No. 1 has increased the belief that broad definitions of “composition” might not be sufficient to define temperature classification adequately.