A contactor for medium voltage electric systems comprising: - one or more electric poles; - for each electric pole, a fixed contact and a corresponding movable contact reversibly movable between a first position, at which said movable contact is decoupled from said fixed contact, and a second position, at which said movable contact is coupled with said fixed contact; - an electromagnetic actuator comprising a magnetic yoke (41, 42) having a fixed yoke member and a movable yoke member, said movable yoke member being reversibly movable between a third position corresponding to the first position of said movable contacts, at which said movable yoke member is decoupled from said fixed yoke member, and a fourth position corresponding to the second position of said movable contacts, at which said movable yoke member is coupled with said fixed yoke member, said electromagnetic actuator further comprising an excitation circuit assembly comprising at least an excitation coil electrically connected with an auxiliary electric power supply, said excitation coil being fed with an excitation current (ii) to generate an excitation magnetic flux to move said movable yoke member from said third position to said fourth position or to maintain said movable yoke member in said fourth position, said excitation coil being not fed with an excitation current (ii) when said movable yoke member moves from said fourth position to said third position; - one or more opening springs operatively coupled with said movable yoke member to move said movable yoke member from said fourth position to said third position, when said excitation coil is not fed with an excitation current (i 1); - a kinematic chain to operatively connect said movable yoke member with said movable contacts; wherein said electromagnetic actuator comprises a damping circuit assembly (45, 47, 48) comprising at least a damping coil and arranged to form a conductive loop at least partially enchained with the excitation magnetic flux generated by the excitation current (ii) flowing along said excitation coil, when said auxiliary electric power supply provides said excitation current to said excitation coil, in such a way that a secondary current (i 2) circulates along said damping coil when said excitation magnetic flux is subject to a transient generated when said excitation coil is fed with a pulse of said excitation current (ii) or when said excitation current (ii) stops circulating along said excitation coil, said secondary current (i 2) having an opposite direction compared to said excitation current (ii) when said excitation coil is fed with said excitation current (ii), said secondary current (i 2) having a same direction of said excitation current (i 1) when said excitation current (i 1) stops circulating along said excitation coil characterised in that said excitation coil and said damping coil are wound around said fixed yoke member. - one or more electric poles; - for each electric pole, a fixed contact and a corresponding movable contact reversibly movable between a first position, at which said movable contact is decoupled from said fixed contact, and a second position, at which said movable contact is coupled with said fixed contact; - an electromagnetic actuator comprising a magnetic yoke (41, 42) having a fixed yoke member and a movable yoke member, said movable yoke member being reversibly movable between a third position corresponding to the first position of said movable contacts, at which said movable yoke member is decoupled from said fixed yoke member, and a fourth position corresponding to the second position of said movable contacts, at which said movable yoke member is coupled with said fixed yoke member, said electromagnetic actuator further comprising an excitation circuit assembly comprising at least an excitation coil electrically connected with an auxiliary electric power supply, said excitation coil being fed with an excitation current (ii) to generate an excitation magnetic flux to move said movable yoke member from said third position to said fourth position or to maintain said movable yoke member in said fourth position, said excitation coil being not fed with an excitation current (ii) when said movable yoke member moves from said fourth position to said third position; - one or more opening springs operatively coupled with said movable yoke member to move said movable yoke member from said fourth position to said third position, when said excitation coil is not fed with an excitation current (i 1); - a kinematic chain to operatively connect said movable yoke member with said movable contacts;