An electric generator having a rotor with permanent magnets, configured for rotating about a rotation axis; a stator having at least one magnetic yoke with arms extending axially inside or outside of the rotor so as to be adjacent to a radial inner or outer side, respectively, of the rotor; wherein the arms of the at least one magnetic yoke are circumferentially distributed so as to form a slot between each pair of adjacent arms, each slot and each arm showing a width. The widths of the arms and/or the widths of the slots have different values distributed along the circumference. The invention is also directed to a valve having the electric generator equipped with a turbine wheel for being driven by a flow of gas in the valve.