Slot/pole combinations choice for concentrated multiphase machines dedicated to mild-hybrid applications

Abstract

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

“…Considering both fault-tolerant capability and power density, the slot/pole combinations for five-phase fault-tolerant PMSMs which satisfy 2p = Q ± 2 (where Q is number of slots, and 2p is number of poles) are proposed [36]. The rotor losses on such slot/pole combinations are thoroughly investigated in [15,19], and the analysis results indicate that in comparison with the low pole-number choice (2p = Q − 2), the high pole-number choice (2p = Q + 2) leads to higher rotor losses, which will reduce the power density. However, for the direct-drive outer-rotor machine used for four-wheel-drive EVs, the space limitation is serious, and compared with a low pole-number choice, the high pole-number choice results in a very shallow rotor core back and creates a "ring" type structure, and the center of the ring can be used to house the cooling system.…”

“…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].…”

“…Due to irregular MMF distribution, FSCW introduces unbalanced radial forces, and this causes considerable vibration and noise. The impacts of slot/pole combination choices on unbalanced radial forces and vibration modes are analyzed in [15]. The radial force density harmonics and vibration characteristics of fractional-slot PM machines are investigated in [23][24][25][26], and since FSCW machines are more susceptible to low frequency resonant vibrations, hence, for EV applications where a silent and smooth operation is required, the characteristics of the magnetic forces should be considered during the machine design process.…”

Comparison and analysis of post-fault operation modes in a five-phase PMSM considering thermal behavior

“…Fig.1-a and Fig.1-b show the 20-slot/14-pole five-phase PMSM [16], in which fractional slot tooth concentrated winding and IPM rotor are used.…”