Abstract A vacuum switch for making and breaking an inductive electric circuit is composed of a highly evacuated envelope and a pair of separable electrodes located within the envelope. At least one of the contacts of the electrodes is made of a sintered alloy essentially composed of a metal carbide, such as tungsten carbide, having low work function, another electrically conductive metal, such as silver, which also offers good machining characteristics, and certain wettable materials which allow the silver to impregnate the tungsten carbide by filling in the interstices between the particles thereof. When the contacts are opened, or separated, the resultant heat of an arc initiated therebetween causes the tungsten carbide to emit thermionic electrons which are effective for ionizing the gas, or metal vapors, emanating from the contact surfaces, whereupon the arc is maintained until the first current zero is reached even when only small currents are flowing through the same and chopping problems are generally prevented.
In a vacuum type switch for maintaining an arc at low current levels comprising a highly evacuated envelope and a pair of separable contacts located in the envelope so as to make and break an electric circuit, the improvement comprising: at least one of the separable contacts being formed of a sintered metal carbide being selected from a group consisting of WC, MoC, ZrC, TiC, VC, SiC, and the combinations thereof, and including a wettable material composed of 0.1 to 5 percent by weight of Ni, 0.1 to 1 percent by weight of Cu and 0.1 to 5 percent by weight of Co, the sintered metal carbide further being impregnated with an electrically conductive metal amounting to between 10 and 60 percent by weight of the total weight of said sintered metal carbide, said wettable material and said electrically conductive material.
Claim 2
Dependent Claim
141 words
In a vacuum type switch for maintaining an arc at low current levels comprising a highly evacuated envelope and a pair of separable contacts located in the envelope so as to make and break an electric circuit, the improvement comprising: at least one of the separable contacts being formed of a sintered metal carbide being selected from a group consisting of WC, MoC, ZrC, TiC, VC, SiC, and the combinations thereof, and including a wettable material composed of 0.1 to 5 percent by weight of Ni, 0.1 to 1 percent by weight of Cu and 0.1 to 5 percent by weight of Co, the sintered metal carbide further being impregnated with an electrically conductive metal amounting to between 10 and 60 percent by weight of the total weight of said sintered metal carbide, said wettable material and said electrically conductive material.
Claim 3
Dependent Claim
16 words
In a vacuum type switch according to claim 1, said electrically conductive material being silver (Ag).