Vacuum switch

A vacuum switch fitted with a vacuum valve comprising:

• an insulation tube to both ends of which is fitted an end plate;
• a fixed-side conductive rod, which is fitted loosely into one side of said insulation tube and a base of which is fixed to a first end plate and a fixed-side contact fixed to a tip of said fixed-side conductive rod;
• a moveable-side conductive rod which is fitted loosely into a second end-plate via a bellows;
• a movable-side contact fixed to a top of said movable-side conductive rod, wherein an outer periphery of said movable-side contact faces an outer periphery of said fixed-side contact;
• and
• a circular third electrode, fitted coaxially at an intermediate part of an inner periphery of said insulation tube, an inner periphery of said circular third electrode between and facing said fixed-side contact and said movable-side contact, wherein when a gap between said fixed-side contact and movable-side contact is d1, one half of a difference between an inner radius of said third electrode and outer diameter of said fixed-side contact and said movable-side contact is d2, a radius of curvature of a chamfered part of an outer periphery of facing sides of said fixed-side contact and movable-side contact is R1, a radius of curvature of said chamfered part of other ends of and inner periphery of said third electrode is R2 and a width of said third electrode in an axial direction is L, then
• d2=(0.4˜0.8)d1
• R1=(0.1˜0.4)d1
• R2=(1.2˜2.0)R1
• L=(0.6˜0.95)d1.