Switching device for medium voltage electric power distribution installations

A switching device comprising:

• one or more fixed contacts and one or more movable contacts, each movable contact being reversibly movable between an opening position, at which said movable contact is decoupled from a corresponding fixed contact, and a closing position, at which said movable contact is coupled with the corresponding fixed contact;
• an electromagnetic actuator adapted to move said movable contacts between said opening and closing positions, said electromagnetic actuator comprising a fixed yoke and a movable armature operatively associated with said fixed yoke to form a magnetic circuit, said movable armature being reversibly movable between a first position, which corresponds to the opening position of said movable contacts, and a second position, which corresponds to the closing position of said movable contacts;
• a kinematic chain to operatively connect said movable armature with said movable contacts;
• wherein said electromagnetic actuator comprises a first excitation coil and a second excitation coil wound around a first section of said fixed yoke and in that said switching device further comprises a first power drive circuit adapted to drive said first excitation coil by providing a first excitation current to said first excitation coil and a second power drive circuit adapted to drive said second excitation coil by providing a second excitation current to said second excitation coil, said first and second power drive circuits being galvanically separated one from another and capable of operation independently one from another,
• wherein said control means are configured to control said first and second power drive circuits so that, to perform a closing manoeuvre of said switching device;
• said first power drive circuit provides a launch pulse of said first excitation current to said first excitation coil at a first launch instant, said launch pulse of said first excitation current having an amplitude lower than the amplitude of an excitation current needed to move said movable armature;
• said second power drive circuit provides a launch pulse of said second excitation current to said second excitation coil at said first launch instant, the launch pulses of said first and second excitation currents having a same amplitude and duration, and
• wherein said control means are configured to control said first and second power drive circuits so that:
• if operation of said first excitation coil is affected by a failure, said second power drive circuit provides a further launch pulse of said second excitation current to said second excitation coil at a second launch instant following said first launch instant, said further launch pulse of said second excitation current having an amplitude equal to the amplitude of the excitation current needed to move said movable armature;
• or
• if operation of said second excitation coil is affected by a failure, said first power drive circuit provides a further launch pulse of said first excitation current to said first excitation coil at a second launch instant following said first launch instant, said further launch pulse of said first excitation current having an amplitude equal to the amplitude of the excitation current needed to move said movable armature.