Investigation of mechanical loss and heat transfer in an axial-flux PM machine

Abstract

This paper investigates components of the mechanical loss together with heat transfer effects in an axialflux PM motor. The mechanical loss components generated within electrical machines are well known, however, their prediction or derivation has not been widely reported in the literature. These, together with the electromagnetic loss sources and heat transfer effects are crucial and must be accounted for when considering high-power density, high-speed and/or compact machine design. This research is focused on separating the mechanical loss components to gain a more in depth understanding of the effects and their importance. Both experimental and theoretical techniques have been employed in the analysis. In particular, hardware tests with dummy rotors have been performed to measure the bearing and windage/drag loss components. These have been supplemented with CFD analysis to theoretically evaluate the aerodynamic effects occurring within the mechanical air-gap accounting for loss and heat transfer. Further to these, a 3D lumped parameter thermal model of the axial-flux PM demonstrator has been developed to validate predictions of the mechanical loss components and heat transfer mechanisms. The theoretical findings show good agreement with experimental data. Moreover, the research outcomes suggest that the mechanical and aerodynamic effects require careful consideration when a less conventional machine design is considered. I.

Experimental calibration in thermal analysis of PM electrical machines

“…The winding assembly incorporates thermal sensors in the middle of the active length (thermocouple 4 and mirrored over the symmetry planes 5, 6, and 7) and at the top, middle and bottom of the end winding (sensors 1-3 and 8-10). The stator core pack, or back iron, is divided in two regions, the tooth (thermocouples [16][17][18][19][20][21] and mirrored over the symmetry plane 27-32) and the yoke (thermocouple [16][17][18][19][20][21] and mirrored over the symmetry plane 27-32). The large number of thermocouples allows for an investigation to be carried out on the influence of the thermal sensor location on the model calibration.…”

“…5. An alternative technique for TEC definition is to make use of the FEM predictions to calculate the average temperature for each model sub-region and the heat flux across the sub-region boundaries [19]. The thermal resistances are then directly obtained from the temperature difference between the sub-regions divided by the heat flux across the boundaries multiplied by the area across which the heat is transferred.…”

3D Thermal Analysis of a Permanent Magnet Motor with Cooling Fans

“…In this paper, a novel and special cooling system design for an axial flux permanent magnet (AFPM) machine is carried out as a case study. In the literature there has been much research on the electromagnetic aspects of AFPM machines, but their thermal performance has not been fully investigated (Mellor et al, 1991;Hendershot and Miller, 1994;Lee et al, 2000;El-Refaie et al, 2004;Boglietti et al, 2005;Mezani et al, 2005;Dorrrell et al, 2006;Trigeol et al, 2006;Yu et al, 2010;Wrobel et al, 2013;Chong et al, 2014;Dong et al, 2014). For other types of electrical machines, there are four methods generally used for thermal analysis.…”

A Computationally Efficient PM Power Loss Mapping for Brushless AC PM Machines With Surface-Mounted PM Rotor Construction

“…Mechanical loss is attributed to the frictional effects within the bearing assembly (bearing loss) and fluid dynamics or aerodynamics effects within the motor body (windage or drag loss) [5]. Electromagnetic losses are usually associated with active parts of the motor assembly and include the iron, winding and permanent magnet (PM) loss components [6]- [8].…”