A.C. machine windings with reduced harmonic content

This paper describes a type of double-layer winding known as an interspersed winding, which may be used in a.c. machines to reduce harmonic components of induced e.m.f. or load m.m.f. The principles underlying the design of interspersed windings are described and compared with the standard analysis of conventional windings in terms of harmonic winding factors. Design and performance details are then given for a complete range of 3-phase interspersed windings covering equivalent values of slots/pole per phase from 4 to 9. It is shown that control of the largest low-order harmonics may be achieved with insignificant alteration to manufacturing methods, and this type of winding should therefore find useful application in large generators and motors where the reduction of stray load losses is an important consideration.