A method of analysing dynamic properties of direct current machines with regard to the real brush width

Abstract

In mathematical models of direct curent machines a point contact between the brush and the commutator is usually assumed ignoring the effect of the armature coils short-circuited by the real brush. This paper presents an analysis of d.c. machines taking into account the real width of the brush. The operation of a real brush covering any number of commutator bars was modelled using ap system of point brushes (the first of which represents the entering edge and thep brush stands for the leaving edge of the real brush) connected together short-circuiting thereby a part of the armature coil. General equations for the machine incorporating this model of the real brush were presented. The chosen transients of the investigated motor were presented and the conclusions formulated on the basis of the proposed model and the numerical calculation carried out.