Brush Wear Modelling in High Speed Universal Motors

The brush wear in small rating, high speed, universal motors is analysed, developing a model for its estimation, as a function of the operating and constructive quantities. Particular attention is devoted to the effect of the turns distribution in the armature slots: to this aim, two universal motors are considered, with the same constructive quantities, except for the number of turns of the two coil sections per layer-slot; in the former motor this number is the same, in the latter different, maintaining nevertheless the same sum. Using a suited equivalent network to study the commutation, the significant figures of merit are found out, giving an explanation of the different wear in the two cases