Uwe Kellner-Werdehausen

Periodic and traveling current-density distributions in high-voltage diodes caused by avalanche injection

Fast switching of high-voltage diodes from the forward-conducting state to the blocking state may result in avalanche injection at diode voltages far below the static breakdown voltage, when the concentration of free charge carriers in the space charge region exceeds the doping concentration. Under such conditions, the current-density may become non-uniform. Our numerical investigations on 3.3-kV and 13-kV diodes show that-depending on the turn-off conditions-diverse current-density patterns may arise. Two completely different types of periodic current-density distributions that may appear in high-power diodes during the reverse recovery period are investigated in detail by means of numerical calculations. Furthermore, the influence of the charge carrier lifetime and thermal effects on the evolution of the current-density patterns emerging from the periodic current-density distribution is discussed

Silicon Thyristors for Ultrahigh Power (GW) Applications

Evolution of thyristor technology and the design concepts, which brought and maintain the phase control thyristor (PCT) at the top of a power pyramid, are discussed. The state-of-the-art device concepts like electrically triggered thyristor and light triggered thyristor are described for voltage classes up to 8.5 kV and maximal on-state rated current of 6 kA. Main focus is laid on the PCTs for high-voltage direct current transmission, the enabler of power transmission beyond the 10-GW level.