270-V Dc Hybrid Switch

High-voltage direct current (dc) power is one of the most efficient, reliable, and lightweight methods to generate and distribute energy. This power system is not in common use today on aircraft or other weight- and reliability-sensitive applications because of difficulties in switching high-voltage dc power. This difficulty becomes acute when switching at high altitude because of the very low mobility of an arc in low pressure. Direct application of power semiconductor switching devices is feasible but would result in severe thermal problems for other than the lowest current applications. A novel switching device is described that overcomes these shortcomings. This device is based on a unique combination of power semiconductor and contact structure switching systems. This hybrid switching device exhibits arcless switching for currents below two times the device rating. Above this current level the contact structure limits the current to a level that can be handled by the power semiconductor. The contact structure develops this currentlimiting capability over a range of pressure from atmospheric to 20 torr. At low pressures a high arc mobility is achieved through a novel approach where the arc develops its own environment. The arc plasma decomposes plastic wall materials to produce an environment that is conducive to high arc mobility.