Analysis of a hybrid excitation DC motor

In some niche applications, e.g. emergency pumps operating in case of fire, a high reliability and a constant speed operation capability are basically required. This paper deals with the use of hybrid excitation in DC motors to permit a highly reliable operation under adjustable field supply and unregulated armature supply, e.g. provided by an emergency accumulator. In fact, the field winding permits to retain a possibly adequate speed regulation capability, while the magnets ultimately allow an uncontrolled operation even in case of full failure of the excitation system. The paper presents a preliminary design and its validation and optimization by means of FEM analysis.