Patent ID: 7977824

Claim:
A device for switching in and out a load with respect to an alternating voltage feeder, said device having at least one mechanical switch in a current path adapted to connect the feeder and the load, as well as a unit adapted to control said switch to close and open for performing said switching in and out, respectively, characterized in that the device comprises a first and a second mechanical switch each adapted to be connected in series in said current path and each having a by-pass branch with at least one member with ability to block current therethrough in at least a blocking direction and conduct current therethrough in at least one direction, a third mechanical switch arranged as a middle switch between and in series with said first and second mechanical switches and with each said at least one member, and that said unit is adapted to control a procedure of a switching out in synchronization with the current in said current path by opening said first mechanical switch when a first said at least one member in parallel therewith is in the conducting state for transferring the current therethrough and opening another mechanical switch of the device in series with said first at least one member when this first member is in the blocking state and to control a procedure of a switching in in synchronization with the voltage in said feeder by, when a second said at least one member in parallel with said second mechanical switch is in the blocking state, closing said third mechanical switch of the device and closing said second mechanical switch when said second at least one member in parallel therewith is in the conducting state; wherein said unit is adapted to control a procedure of said switching out by starting from a state in which the first, second, and third mechanical switches are closed and to control said first mechanical switch to open when said first at least one member in parallel therewith is in a conducting state for transfer of the current therethrough and to control said third mechanical switch to open when said first at least one member is in the blocking state; and to control a procedure of a switching in by controlling said first mechanical switch to close, then said third mechanical switch to close when said second at least one member associated with the second mechanical switch is in the blocking state and finally said second mechanical switch to close when said second at least one member in parallel therewith is in the conducting state.