Suppression of Electron Emission and Secondary Electron Multiplication to Improve the Flashover Voltage of Vacuum Interrupter by Surface Coating Modification

Vacuum surface flashover at high voltage limits the development of vacuum interrupter(VI) towards high voltage and miniaturization. In order to improve the vacuum surface flashover voltage of the vacuum interrupter, the Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coatings is constructed at the shield ring to suppress electron emission, and Cr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating is constructed on the surface of the ceramic shell to suppress secondary electron multiplication by atmospheric plasma spraying. The effect of the coatings on the vacuum surface flashover characteristics is studied. The conditioning characteristics of flashover voltage and voltage-current waveforms under positive impulse voltage before and after coating construction are compared. The change of work function before and after the construction of alumina coating at the shield ring and the change of secondary electron emission coefficient before and after the construction of Cr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating on the surface of ceramic shell were measured. The results show that the construction of Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating at the of the shield ring improves the surface flashover voltage of the VI. The insulation characteristics of the 40μm thick Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating are better than that of the 20μm thick Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating, but the vacuum surface flashover characteristics of the 100μm thick coating are deteriorated. The construction of Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating at the end of the shield increased the work function of the shield ring from 4.51 eV to 5.39 eV. Cr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> coating along the surface of the ceramic shell reduces the maximum secondary electron emission coefficient of the ceramic shell from 6.4 to 1.49, thus improved the surface insulation characteristics of the vacuum interrupter.