Fatigue life simulation of vacuum interrupter bellows subjected to high gas pressure and high operating velocity

A design gauge pressure of an eco-friendly gas insulated switchgear (GIS) with an application of vacuum interrupters (VIs) ranges from 0.1 to 0.3MPa. Therefore, a high differential pressure is imposed on bellows of the VIs, which increases the fatigue failure risk of the bellows after cycles of operations. Although, there are some empirical equations recommended by the Chinese National Standard GB/T 12777-2008 which can be used to evaluate the fatigue life of the bellows, there still remains little understanding on the fatigue life of the bellows when the VI is subjected to a high differential pressure and a high operating velocity. The objective of this paper is to determine the relationship between the fatigue life of bellows and high differential pressure and high operating velocity. A fluid-structure interaction simulation is set up to analyze the equivalent stress and the fatigue life of VI bellows under differential gauge pressure ranging from 0.1MPa to 0.3MPa, and under differential operating velocity ranging from 2m/s to 4m/s. The simulation result shows that with an increasing of the pressure and operating velocity, the equivalent stress increases and the fatigue life decreases from 47957 cycles under 0.1MPa and 2m/s to 489 cycles under 0.3MPa and 4m/s. At last, a comparison between the simulation result and the empirical equations shows a limitation of the empirical equations, in which there is lacking of the operating velocity.