IEEE 620-1987

2.1 This guide defines thermal limit curves, recommends a standard procedure for construction of the curves, and provides the definitions and information necessary to properly use these curves. 2.2 The guide also describes thermal limit curves for large squirrel-cage motors defined as those motor ratings built in frames larger than the frame normally used for 500 hp, 1800 r/min motors.

The purpose of this guide is to assist in a uniform understanding of the construction, interpretation, and use of motor thermal limit curves.

New IEEE Standard - Inactive-Withdrawn. Thermal limit curves for induction machines are defined. A procedure is established for the presentation of these curves, and guidance for the interpretation and use of these curves for machine thermal protection is provided.