Considerations on Selecting Fractional-Slot Nonoverlapped Coil Windings

Abstract

This paper focuses on the selection of a fractional-slot winding for permanent-magnet (PM) machines. The choice of the proper combination of the number of slots and number of poles, together with the corresponding winding layout, has a strong impact on the PM machine performance, in terms of torque density, torque ripple, magnetomotive force harmonic content, and induced rotor losses, as well as the capability to limit the short-circuit current and other fault-tolerance features. Considering these characteristics, this paper aims to help the PM machine designer to select the proper winding configuration, giving useful indications. The winding choice criteria are given using analytical equations, so that their implementation is easy. In this way, the collection of such criteria becomes a helpful tool in the design process

Application of Fractional-Slot Concentrated Windings to Synchronous Reluctance Motors

“…Reduction of these MMF space harmonics may be possible by using a 4 layer winding with tooth-wound [36]. This would imporve the saliency, power factor and torque capability but would increase manufacturing complexity and increase cost.…”

Research on a 20-Slot/22-Pole Five-Phase Fault-Tolerant PMSM Used for Four-Wheel-Drive Electric Vehicles

“…For the chosen 20-slot/22-pole winding configuration, the winding factor of single-layer winding is 0.9877, which is a little higher than that of double-layer winding, i.e., 0.9755. But double-layer winding features advantages in rotor losses and mechanical balancing [15,16], combining the high-efficiency requirement of EV applications, the 20-slot/22-pole double-layer winding configuration is further investigated in this paper. …”

“…But FSCW also introduces many lower and higher order space harmonics, which have negative effects on machine performance, including localized saturation, eddy current losses in permanent magnets (PMs), possible resonance and noise, etc. The impacts of slot/pole combinations and magneto-motive force (MMF) harmonics on rotor eddy current losses in concentrated winding PM machines were analyzed by Aslan and Semail and Bianchi and Fornasiero, respectively [15][16][17][18]. By studying the interaction between MMF harmonics wavelengths and PM pole dimensions, a general analytical model of PM eddy-current losses is developed for comparison of multiphase PM machines [19,20].…”

Reduction of Eddy Current Loss of Permanent-Magnet Machines With Fractional Slot Concentrated Windings

“…Considerable efforts have been devoted to investigating and reducing those harmonics, including: 1) using multi-layer tooth concentrated winding and shifting the winding systems by a specific number of slots [11][12][13]; 2) using different turns per coil or different turns per coil-side [14]; 3) modifying the stator yoke in specific locations by using magnetic flux-barriers in stator yoke [14]; 4) doubling the number of stator slots and using two winding systems [15,16], 5) using delta-star windings with different turns per coil [17,18]; 6) using the multiple three-phase concentrated windings [19][20][21]. Although these techniques have been adopted, the FSCW PM machines still suffer from either sub-or high MMF harmonics.…”