Semiconductor switching device

A 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 a power system, wherein input terminals of a DC voltage converter are connected in parallel to the capacitor, and output terminals of the DC converter are connected to power input terminals of a gate drive circuit for driving the semiconductor switching elements, the DC voltage converter converting a voltage stored in the capacitor to a voltage driving a source controlling at least one of the self-quenching semiconductor switching elements.

A 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 a power system, wherein the non-linear circuit comprises series connected non-linear units and the capacitor comprises series connected capacitors, each of which is connected in parallel with one of the non-linear units, input terminals of a DC voltage converter are connected in parallel to at least one of the capacitors at a lower voltage side, and output terminals of the DC voltage converter are connected to power input terminals of a gate drive circuit for driving the semiconductor switching elements, the DC voltage converter converting a voltage stored in the capacitor to a voltage driving a source controlling at least one of the self-quenching semiconductor switching elements.

A 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 a 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 a power system, wherein the diode is a large Qrr diode, in which reverse recovery charge is at least 10 percent of forwardly flowing charge when the semiconductor switching element turns off.