Abstract
In this paper, a set of correlations for the windage power losses in a 4 kW axial flux permanent magnet synchronous machine (AFPMSM) is presented. In order to have an efficient machine, it is necessary to optimize the total electromagnetic and mechanical losses. Therefore, fast equations are needed to estimate the windage power losses of the machine. The geometry consists of an open rotor–stator with sixteen magnets at the periphery of the rotor with an annular opening in the entire disk. Air can flow in a channel being formed between the magnets and in a small gap region between the magnets and the stator surface. To construct the correlations, computational fluid dynamics (CFD) simulations through the frozen rotor (FR) method are performed at the practical ranges of the geometrical parameters, namely the gap size distance, the rotational speed of the rotor, the magnet thickness and the magnet angle. Thereafter, two categories of formulations are defined to make the windage losses dimensionless based on whether the losses are mainly due to the viscous forces or the pressure forces. At the end, the correlations can be achieved via curve fittings from the numerical data. The results reveal that the pressure forces are responsible for the windage losses for the side surfaces in the air-channel, whereas for the surfaces facing the stator surface in the gap, the viscous forces mainly contribute to the windage losses. Additionally, the results of the parametric study demonstrate that the overall windage losses in the machine escalate with an increase in either the rotational Reynolds number or the magnet thickness ratio. By contrast, the windage losses decrease once the magnet angle ratio enlarges. Moreover, it can be concluded that the proposed correlations are very useful tools in the design and optimizations of this type of electrical machine.
Highlights
Axial flux permanent magnet synchronous machines (AFPMSMs) are quite modern devices with extensive flexibility at high-speed-low-torque and at low-speed-high-torque applications [1,2,3]
The results of the correlations for the variations of windage losses due to viscous forces for the surfaces in the gap are compared with the results reported by Wrobel et al [21] in Figure 9, and a good agreement is observed
The windage power losses in an axial flux permanent magnet synchronous machine have been studied in this research paper
Summary
Axial flux permanent magnet synchronous machines (AFPMSMs) are quite modern devices with extensive flexibility at high-speed-low-torque and at low-speed-high-torque applications [1,2,3]. Carried out a computational fluid dynamics (CFD)-parametric study to calculate the windage losses in an AFPMSM concerning variable magnet thickness He showed that an increase in the magnet groove depth from 2 to 18 mm can noticeably raise the windage losses (up to 60 W) through the generator with the rotor diameter of 220 mm, gap size distance of 2 mm and the angular velocity of 1500 rpm. Wrobel et al [21] performed CFD simulations to assess the windage losses in an AFPMSM They investigated the aerodynamic effects occurring within the air-gap. CFD simulations are performed for the practical ranges of geometrical parameters including the magnet thickness, the magnet angle, the air-gap distance as well as the rotational speed of the rotor. Details of the proposed method and the results are discussed
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