Polyphase electric rotary machine

Multi-phase rotating electric machine able to be used in a motor vehicle with an internal-combustion engine, on the one hand, as an electrical generator and, on the other hand, as an electric motor for starting of the internal-combustion engine, including a shaft (3) carrying a rotor (4) with magnetic poles surrounded by a multi-phase stator (8) carried internally by a hollow support (S) equipped with a front end plate (13) and with a rear end plate (14) which are linked together and each centrally possess an end-plate means (11, 12) traversed by the end of the shaft (3) carrying the rotor (4), in which means (50, 52) of the magnetic type for tracking the rotation of the rotor are provided and include at least one sensor (52) associated with a target (50), characterised in that the target (50) is a target with axial or radial reading, in that the target (50) is fixed onto a target holder (60) locked in rotation onto the rotor (4) and is installed axially between the rotor (4) and one of the front (13) or rear (14) end plates adjacent to the target holder (60), and in that the front (13) or rear (14) end plate adjacent to the target holder (60) carries the sensor (52) detecting the passing of the magnetic target (50).