Strain Analysis of Vacuum Interrupter Bellows

Abstract

The vacuum interrupter (VI) is the main part of the vacuum circuit breaker (VCB), and an essential component of its design is the bellows. In future high-voltage VCBs, faster switching speeds will lead to higher dynamic impact-type loads, and the oscillation of the bellows after the contact opening and closing could shorten the mechanical life of the bellows. This article provides a 1D computer-aided engineering (CAE) analysis of the strain of the bellows oscillation in a VI caused by the axial load from the impact of the contact. A formula for the oscillation is derived using the longitudinal vibration response of a mass-spring 1D model, calculated by the convolution integral of the input and the impulse response function of the vibration modes. The proposed 1D analysis was verified and shown to be effective under four different experimental conditions. This article also provides a 1D CAE analysis of the mechanical life of the bellows. These 1D analyses estimate the effect of stress reducing countermeasures on the bellows' lifetime without increasing its size.