Abstract: How to shorten the pumping time and reduce the cost under the premise of ensuring the vacuum impregnation quality of capacitors is a problem that every capacitor manufacturer pays close attention to. For a long time, because there is no objective measurement data to effectively judge the vacuum impregnation end point, the vacuuming stage time is often prolonged. This paper describes the development results of a water molecular mass spectrometer. From the molecular weight level, the vacuum impregnation endpoint of the capacitor was judged. The number of vapor molecules of the pumped gas can be measured and calculated, and thereby achieving an accurate and effective judgment of the endpoint of the vacuum immersion process.

Key words: vacuum impregnation, vacuum endpoint determination, mass spectrometry, residual gas, water mass spectrometer