"自动停机装置" can be translated as "automatic shutdown device" or "automatic stop mechanism" in English, depending on the specific context and the level of formality required.
Automatic shutdown device is a more straightforward and commonly used term, especially in technical or engineering contexts.
Automatic stop mechanism emphasizes the mechanism or process that causes the shutdown, which might be more appropriate in certain detailed descriptions or technical documents.
Both expressions are accurate and can be used interchangeably in most cases.