The invention relates to a permanent magnet synchronous motor, in particular an electric three phase motor, comprising a stator in which stator teeth with interposed stator grooves are arranged, at least one winding made of an electrically conductive material being provided on each stator tooth, further comprising a rotor with permanent magnets which are arranged radially in a spoke-like manner in the rotor. Said synchronous motor has a predetermined and defined maximum brake torque based on a predetermined diameter-length-ratio of the rotor, a number of rotor poles and a number of stator grooves. The present invention further relates to an electric power-assisted steering system.