Patent ID: 6960844
Filing Date: 2005-11-01
Classification: H01H

Abstract:
1. An electric switching device for alternating current comprising at least two contact members arranged in a current path through the switching device and a semiconductor device able to block current therethrough in at least a first blocking direction and a unit adapted to control opening of a current path through the switching device by controlling a first of the contact members to open for transferring the current through the switching device to the semiconductor device when this is in or going into the conducting state and then the second contact member to open when the semiconductor device is in a state of blocking current therethrough for breaking the current through the switching device, wherein the total number of contact members of the switching device are at least four with two connected in series in each of two branches connected in parallel in said current path, the semiconductor device being arranged to connect the midpoints between the two contact members of each branch to each other, the switching device comprises at least a member adapted to detect the direction of the current through the switching device, the control unit being adapted to control opening of the current path by controlling the first contact member located before said midpoint with respect to the current direction prevailing of one first branch to open and a second contact member of the second branch located after the midpoint with respect to the current direction to open for transferring the current to a temporary current path through the semiconductor device when this is in or going into the conducting state and then break the current path through the switching device when the semiconductor device is in a state of blocking current therethrough by opening at least one contact member of the switching device arranged in the temporary current path through the semiconductor device, and the control unit being adapted to chose which branch shall be the first one on the basis of information from the detecting member.