Abstract: To improve commutation and, particularly, to suppress commutator sparking and arc-over or flash-over, an auxiliary yoke is placed between the main poles and the auxiliary or commutating poles of a salient pole machine, the auxiliary yoke being formed of stacked lamellae, preferably with an adjustable air gap. Adjustability can be obtained by forming the auxiliary yoke with two interengaging sections, one of which is movable with respect to the other, so that commutation at the specific poles can be adjusted by adjusting the air gap of the auxiliary yoke.