Electric strength of vacuum systems with Co-Mo alloy coated Cu electrodes

The paper presents the results of investigations of the electric strength at 50 Hz AC voltage of vacuum insulation systems that were not subjected to conditioning. The experiments have shown that a Co-Mo alloy coating electrolytically deposited on the surface of copper electrodes causes, at the pressure 2 mPa, >25% increase of electric strength of unconditioned vacuum insulation systems. This breakdown strength decreases with increasing gap spacing between the electrodes, and amounts ~17 kV/mm for systems with Cu electrodes at the electrode gap of 1 mm, and ~9 kV/mm at a gap of 6 mm. Plane electrodes with rounded-off edges of Rogowski´s profile were used in the investigations. The electrodes with 50 mm diameter, were made of OFHC Cu. The paper shows the influence of the value of pressure from ~1 mPa to 1 Pa and at constant pressure of ~1 mPa, the length of vacuum gap, and the presence of a Co-Mo alloy layer coating the electrodes