Clamping system of special conductors (S1, S2, S3) for a stator or rotor bar winding (U1, S1, S2, S3) for an electric machine, such as connection terminals, jumpers, neutrals or star points, etc., suitable for clamping said special conductors (S1, S2, S3) during a twisting step and/or a step of picking up such conductors from a twisting device, said clamping system comprising: - a system axis (T-T); - a plurality of grippers aligned or adapted to be aligned along a circumference lying on a plane substantially perpendicular to the system axis (T-T), each gripper including a pair of jaws or holding arms (32, 33) mounted so as to be mobile in a plane transversal to said system axis (T-T); and - actuation elements (50, 60, 70, 80, 90) of the grippers adapted to be activated to make each gripper take up an operative clamping configuration, in which said holding arms (32, 33) are relatively closer together to clamp on two opposite sides a portion of at least one of said special conductors (S1, S2, S3), and an operative release configuration, in which said holding arms (32, 33) are relatively farther apart to release said portion of the special conductor (S1, S2, S3); said clamping system being characterised in that: - each of said grippers comprises a gripper body slidably mounted along a sliding direction transversal to the system axis (T-T), the gripper body including a body portion to which said holding arms (32, 33) are independently hinged and being suitable for taking up a position relatively more advanced towards the system axis (T-T) when the gripper takes up said clamping configuration, and a position relatively more set back with respect to said advanced position when the gripper takes up said release configuration; and - comprises automatic closing elements and automatic opening elements of the arms (32, 33) of the grippers, said automatic closing elements comprising a forced passage arranged frontally to each pair of holding arms (32, 33) and suitable for engaging such arms (32, 33) during the sliding of the gripper body towards said advanced position to make the gripper take up said clamping configuration, and said automatic opening elements comprising elastic elements connected to said pair of holding arms (32, 33) and suitable for spreading apart such arms (32, 33) while the gripper slides towards said set back position leaving the forced passage so as to allow the gripper to take up said release configuration. - a system axis (T-T); - a plurality of grippers aligned or adapted to be aligned along a circumference lying on a plane substantially perpendicular to the system axis (T-T), each gripper including a pair of jaws or holding arms (32, 33) mounted so as to be mobile in a plane transversal to said system axis (T-T); and - actuation elements (50, 60, 70, 80, 90) of the grippers adapted to be activated to make each gripper take up an operative clamping configuration, in which said holding arms (32, 33) are relatively closer together to clamp on two opposite sides a portion of at least one of said special conductors (S1, S2, S3), and an operative release configuration, in which said holding arms (32, 33) are relatively farther apart to release said portion of the special conductor (S1, S2, S3); an operative clamping configuration, in which said holding arms (32, 33) are relatively closer together to clamp on two opposite sides a portion of at least one of said special conductors (S1, S2, S3), and an operative release configuration, in which said holding arms (32, 33) are relatively farther apart to release said portion of the special conductor (S1, S2, S3); - each of said grippers comprises a gripper body slidably mounted along a sliding direction transversal to the system axis (T-T), the gripper body including a body portion to which said holding arms (32, 33) are independently hinged and being suitable for taking up a position relatively more advanced towards the system axis (T-T) when the gripper takes up said clamping configuration, and a position relatively more set back with respect to said advanced position when the gripper takes up said release configuration; and - comprises automatic closing elements and automatic opening elements of the arms (32, 33) of the grippers, said automatic closing elements comprising a forced passage arranged frontally to each pair of holding arms (32, 33) and suitable for engaging such arms (32, 33) during the sliding of the gripper body towards said advanced position to make the gripper take up said clamping configuration, and said automatic opening elements comprising elastic elements connected to said pair of holding arms (32, 33) and suitable for spreading apart such arms (32, 33) while the gripper slides towards said set back position leaving the forced passage so as to allow the gripper to take up said release configuration. said automatic closing elements comprising a forced passage arranged frontally to each pair of holding arms (32, 33) and suitable for engaging such arms (32, 33) during the sliding of the gripper body towards said advanced position to make the gripper take up said clamping configuration, and said automatic opening elements comprising elastic elements connected to said pair of holding arms (32, 33) and suitable for spreading apart such arms (32, 33) while the gripper slides towards said set back position leaving the forced passage so as to allow the gripper to take up said release configuration.