Influence of opening velocity on interruption capacity of intermediate-frequency vacuum switches with consideration of metal vapor density

The interruption capacity of intermediate-frequency (IF) vacuum switches is significantly affected by contact opening velocity and metal vapor density. However, systematic experimental validation of their interaction mechanisms remains limited. In this study, a dedicated IF drawn-arc platform is developed, and interruption experiments are conducted at 4–14 kA RMS under three distinct opening speeds. A transient numerical model is established to compute the metal vapor density at the current zero point (CZP). Based on experimental measurements and numerical modeling, the metal vapor density at CZP is quantitatively analyzes as a function of opening speed and frequency, and critical opening speed configurations are proposed to ensure safe interruption in IF systems. A map of opening speed, current, and frequency was constructed using the critical vapor density criterion, and the calculated safety margins were in good agreement with experimental results. For a 20 mm diameter CuCr25 flat contact, the required speed increases from 0.44 m/s at 360 Hz to approximately 2.20 m/s at 800 Hz for 10 kA RMS interruption. This study establishes that opening velocity governs interruption performance by controlling metal vapor density, thereby providing both a predictive framework for contact velocity design and a quantitative basis for optimizing aviation IF vacuum switches.