Available Technology

High-Power/Pulsed-Power Electrical Switch

Mercury-free ignitron for fast switching under high voltage/current
Ignitrons are high-current switches that can open and close very quickly by using vaporized-metal plasma arcs to complete a circuit. Mercury is typically used because it does not tend to plate out the internal surfaces of the ignitron structure and cause a short-circuit pathway, permanently closing the switch. Mercury is toxic, making the ignitrons difficult to manufacture, dispose of, and service. Gallium and its alloys have been considered as alternatives to mercury. Not only are they liquid at typical use temperatures like mercury, but they exhibit a lower vapor pressure to withstand even higher voltages. The key obstacle is that using gallium or its alloys in typical ignitron designs results in rapid plating of internal surfaces and premature failure of the switch. The NASA innovation overcomes this obstacle through the use of a novel internal structure of the ignitron that prevents plating of the liquid metal on inner surfaces. Ignitrons are capable of conducting high currents and withstanding high voltages, thus providing high, instantaneous power over a very short time. Such pulsed-power applications as pulsed lasers, pulsed fusion, and power rectification are important to NASA. Other defense, industrial, and commercial applications can benefit from this NASA innovation as well.
Patent Abstract: 
Ignitron electrical switches have traditionally been used in a number of industrial applications in which the high-speed switching of electrical current under high voltage is needed. Today, many of these applications are served by solid-state, semiconductor-type switches, in part due to the toxicity of the mercury used in ignitrons and the lack of suitable alternative designs. On the whole, however, ignitrons can offer much greater durability and reliability over solid-state switch designs, and can handle even higher speeds and higher voltages. NASA scientists have developed a novel ignitron design that uses nontoxic gallium and gallium alloys. The design circumvents plating problems typically experienced with these metals that could lead to short-circuit reliability and durability problems. The result of the NASA innovation is an electrical switch that is ideally suited to the ultra-fast switching of high currents under very high voltages.
Benefits 

Provides an electrical switch that can operate at very high switching speed and high current while withstanding extremely high voltages

applications 

Energy and power: circuit protection systems in the electric power grid

Military: high-power and pulsed-power applications

Materials: high electric power and pulsed power for materials processing

Reps: 
Patent Number: 
8,710,726
Internal Laboratory Ref #: 
MFS-TOPS-56
Patent Status: 
Patent Issue Date: 
September 1, 2015
Agency
NASA
Region
Southeast
State: 
Alabama
Phone: 
256-544-9151
Email: 
terry.taylor@nasa.gov
Lab Representatives
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