Impact of Winding Layer Number and Slot/Pole Combination on AC Armature Losses of Synchronous Surface PM Machines Designed for Wide Constant-Power Speed Range Operation

This paper examines the impact of the winding layer number (single- and double-layer), and magnet type (sintered and bonded), as well as slot/pole combinations on AC stator losses in surface permanent magnet (SPM) synchronous machines equipped with fractional-slot concentrated windings that are designed for wide speed ranges of constant-power operation. It is shown that the use of bonded magnets instead of sintered magnets tends to increase the AC losses, while magnetic saturation of the tooth-tips tends to reduce these losses. The effect of terminal conditions, i.e. series and parallel connections, on AC losses is also investigated. The effect of leakage flux on AC losses is studied for the various slot/pole combinations within the same slot/pole/phase (spp) family as well as for different spp values, indicating that high numbers of stator poles tend to increase the AC losses. An AC loss index has been defined incorporating these effects to serve as a quick screening tool for the various slot/pole combinations under consideration.