Abstract: A composable protection and control apparatus for motors is provided with a power case including semiconductor switches controlling the switching on and off of the power of the phase currents as well as a detector for detecting all or part of these currents and a control module which can be removably fixed to said case and be connected to the switches and to the detector. This module contains a logic circuit for managing the switches which includes a circuit for identifying the size of the power case and a circuit for selecting the working characteristics of the apparatus as a function of this size.