448 / 2017-05-02 11:19:35

Fatigue Life of Bellows in a Vacuum Interrupter Subjected to High Gas Pressure and High Operating Velocity

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A design gauge pressure of a novel gas insulated switchgear (GIS) with an application of vacuum interrupters (VIs) ranges from 0.1 MPa to 0.3 MPa. In this case, a high differential pressure imposes on a bellows of the VI, which increases the risk for the bellows leaking from being fatigue failure after cycles of operation. Although, some empirical equations recommended by the Chinese national standard GB/T 12777-2008 are usually used to evaluate the fatigue life of the bellows. There still remains little understanding on the fatigue of the bellow in the VI, especially when the VI is subjected to a high differential pressure and a high operating velocity. The objective of this paper is to determine the fatigue life of the bellows in the VI under the high differential pressure and the high operating velocity. A U-type bellow is used in our investigation, with an inner diameter of 65 mm and an outer diameter of 90 mm. The thickness of the bellow is 0.2 mm, and the compressed stroke is 20 mm. The material of the bellow is 1Cr18Ni9Ti. Three kinds of differential pressure of 0.1 MPa, 0.2 MPa and 0.3 MPa are assigned, respectively. The operating velocity is assigned ranging as 2.0 m/s, 3.0 m/s and 4.0 m/s. A fluid-structure interaction analysis is performed in order to investigate the dynamic stress distribution over the bellow structure during the operating process. The stress concentration is analyzed under different kinds of pressure and operating velocities. The fatigue life of the bellow is simulated based on an E-N characteristic.