IEEE 117-1974

The chief purpose of this test procedure is to classify insulation systems in accordance with their temperature limits by test, rather than by chemical composition. The intention is, Þrst to classify according to the recognized thermal classiÞcation A, B, F, H, and above H categories as referenced in the Appendix. The motorette procedure is intended to be used as an Industry Standard for insulation systems in that data obtained in accordance with this standard can be correlated between testing laboratories. A wide variety of synthetic electrical insulation materials is available for application in electric machinery and apparatus. As there is a growing tendency either to rely solely on these materials as electrical insulation, or to employ them with the old familiar materials in novel combinations, there is a corresponding increase in the problems associated with the selection and evaluation of insulations. Consequently a complete insulation system must be evaluated rather than testing only individual insulating materials. Many of the specifications regulating the use of insulation materials were written before the advent of the newer synthetics and were based upon experience gained with the old materials over a long period of time. Difficulties arise, therefore, when an effort is made to classify these new materials or combinations for insulation purposes under IEEE Std 1-1969 General Principles for Temperature Limits in the Rating of Electric Machinery and supplementary documents IEEE Std 98-1972, Guide for the Preparation of Test Procedures for the Thermal Evaluation and Establishment of Temperature Indices of Solid Electric Insulating Materials, and IEEE Std 99-1970. Guide for the Preparation of Test Procedures for the Thermal Evaluation of Insulation Systems for Electric Equipment. A wide range of properties is available in current synthetic materials, so that it is not feasible to classify them on the basis of their chemical composition alone. Secondly, it is not desirable to wait and acquire the knowledge required to classify them solely on the basis of experience. In the third place, composite systems of insulation, in which materials of different temperature classes are used in different parts of the structure, may give satisfactory service at temperatures higher than normally permitted for the lowest temperature component; and, conversely, compatibility or otherre problems may arise whereby the highest temperature component is rendered unsuitable for use at its classified temperature.This test procedure has been prepared to outline useful methods for the evaluation of systems of insulation for randomwound stators of rotating electric machines. It is expected that the several insulating materials, or components, making up any insulation system to be tested will Þrst be screened in accordance with speciÞc test procedures for each type of material. Normally materials that have given acceptable performance in these separate screening tests would be included in the system evaluation tests outlined in this procedure. This procedure is intended to evaluate insulation systems for use in "usual service conditions" with air cooling. It has also been a useful tool for evaluating systems for special requirements where machines are enclosed in gas atmospheres, subjected to strong chemicals, to metal dusts, or submersion in liquids. However, these special requirements are beyond the scope of this test procedure.

Revision Standard - Inactive-Withdrawn. Useful methods for the evaluation of systems of insulation for random-wound stators of rotating electric machines are given. The chief purpose is to classify insulation systems in accordance with their temperature limits by test, rather than by chemical composition. The procedure is intended to evaluate insulation systems for use in usual service conditions with air cooling. It has also been a useful tool for evaluating systems for special requirements where machines are enclosed in gas atmospheres, subjected to strong chemicals, metal dusts, or submersion in liquids, although these special requirements are beyond the scope of this test procedure.