The invention discloses a switching device (3) for disconnecting or connecting an electric machine (10), a converter 10 or a plurality of electrical loads supplied with AC power from a power supply (4) and controlled by a control unit (6). The switching device comprises a current sink (2)and at least one mechanical switch (1) in the switching device (3) are arranged in a circuit. The current sink is arranged, upon receipt of a signal, to close and sink the current, and the at least one mechanical switch (1) is arranged to open and break the current on receipt of a signal to open supplied to the electric machine (10) when the current load is at or close to zero.In other aspects of the invention a method and a computer program for carrying out the method are described.