Semiconductor switching device

Abstract

Self-quenching switching elements are connected in series in a semiconductor switching device. Snubber circuits including a diode, a capacitors, and a non-linear circuit are connected in parallel with the respective semiconductor switching elements. In the snubber circuit, the diode and the capacitor are connected in series, and the non-linear circuit is connected in parallel with the capacitor. The non-linear circuit includes an impedance element, a Zener diode, and a controlling semiconductor element and draws current through the controlling semiconductor element when applied voltage exceeds the Zener voltage of the Zener diode. The Zener voltage is larger than a divided voltage applied to the semiconductor element during a fault in a power system.

1 . A semiconductor switching device connected to receive power from a power system producing a voltage that rises when a fault occurs in the power system, the semiconductor switching device comprising: 
 self-quenching semiconductor switching elements connected in series, and    snubber circuits connected in parallel to respective semiconductor switching elements, each snubber circuit comprising a diode and a capacitor connected in series, and a non-linear circuit connected in parallel with the capacitor, said non-linear circuit drawing current when an applied voltage exceeds a clamp voltage, wherein the clamp voltage is at least 1.27 times larger than a divided voltage normally applied to each of the semiconductor elements, and which is larger than a divided voltage applied to one of the semiconductor elements during a fault in the power system.    
   
   
       2 - 12 . (Cancelled).  
   
   
       13 . The semiconductor switching device of  claim 1 , wherein the diode is replaced with a power regeneration switch.  
   
   
       14 . (Cancelled).  
   
   
       15 . The semiconductor switching device of  claim 1 , including a diode-on delay device connected to the diode, in parallel.