3D Finite Element Analysis Method for the Characterization of Axial Flux Permanent Magnet Synchronous Machines: Application to Hybrid Electric Vehicles
Résumé
In the context of vehicle electrification, car manufacturers are facing ever more constraining
standards. Consequently, embedded electrical machines which are critical
components of a vehicle power system have to be highly efficient and remain at an
acceptable cost. In the HEV and EV markets, permanent magnet synchronous machine
(PMSM) have now reached a major place thanks to their high torque/power
density, their high efficiency and their large constant power speed range capability
(Z.Q. Zhu and D. Howe, ”Electrical Machines and Drives for Electric, Hybrid,
and Fuel Cell Vehicles” in Proceeding of the IEEE, Vol. 97, No 4, 2007). Axial
flux permanent magnet synchronous machines (AFPM) provide high compactness
and high torque capability, due to their particular disc-shaped geometry, and consequently
appear as a relevant solution for HEV (A. Cavagnino, M. Lazzari, F.
Profumo and A. Tenconi. ”A Comparison Between the Axial Flux and the Radial
Flux Structures for PM Synchronous Motors”, in IEEE Transactions on Industry
Applications, Vol. 38, No. 6. 2002). However, 3D aspects relative to an axial flux
machine electromagnetic problem are to be considered for an accurate analysis.
Therefore, 3D-FEA is required though their computation is time consuming.
For a variable-speed traction application, requirements usually comprise torque/power
versus speed profiles and voltage and current inverter rankings. FEA is then an efficient
way to check these requirements and to know better the machine characterics
as well. At this point, it is not obvious to decide which simulation is necessary (e.g.
magneto-static or magneto-dynamic application) and what are the interesting values
to analyse each time. Moreover, it is important to choose a convenient configuration
of the simulation and to determine an efficient simulation sequence. This problem
becomes even more relevant when several machines are to be compared. In this
perspective, this paper proposes a methodology to deal with 3D-FEA of an AFPM
machine using CEDRAT-Flux3D
R commercial software. According to the design
requirements, it is explained the necessity of each simulation, and the sequence in
which it should be achieved. A particular emphasis on simulation configuration (i.e.
meshing and parametric discretization) is provided. Finally, a comparison between
a surface mounted permanent magnet synchronous and an interior permanent magnet
synchronous machine, both axial flux structures, is proposed to illustrate the
approach. Problem definition and solving processes times are given to show how
this methodology can be profitable.