This article reviews the history of thermal aging studies of rotating machine insulation, describes how the thermal classes are determined, and identifies some issues with the process that often are not fully understood.

中文翻译：

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确定旋转机械绝缘系统热等级的方法是否有意义？

本文回顾了旋转电机绝热材料的热老化研究的历史，描述了如何确定热等级，并确定了过程中经常无法完全理解的一些问题。