The present invention relates to armature windings for DC electrical machines, and in particular to those that use electronic commutation and have relatively few slots per pole-pair. The armature windings are particularly well suited for use with rotating DC electrical machines that have a large diameter and a large number of poles such as those that might be directly coupled to the turbine blade assembly of a wind turbine. The armature winding is arranged in relation to the magnetic field generated by a field winding or by permanent magnets such that a number of commutation events during the time taken for the relative movement between the armature and the field system of one pole-pair is much larger than the number of coils per pole-pair.