2019-Sustainable Industrial Processing Summit
SIPS2019 Volume 13: Composite, Ceramic, Nanomaterials, Polymers, and Mathematics
| Editors: | F. Kongoli, M. de Campos, S. Lewis, S. Miller, S. Thomas |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2019 |
| Pages: | 171 pages |
| ISBN: | 978-1-989820-12-4 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Magnetic Materials employed in Electric Vehicles
Marcos de Campos1; Jose Adilson de Castro1;1UFF - FEDERAL FLUMINENSE UNIVERSITY, Volta Redonda, Brazil;
Type of Paper: Regular
Id Paper: 207
Topic: 16
Abstract:
A subject of recent interest nowadays is electric and hybrid cars. Most of the high-efficiency motors use magnets in the rotors because this saves the current used in the magnetization of the soft magnetic material. The IE4 European efficiency specification (Super Premium Efficiency) also request motors with magnets in order to achieve the specifications of the manufacturers. Thus, it is forecasted that the market of magnets for electric motors should increase considerably in the forthcoming years.
The electric vehicles industry put emphasis on the optimization of batteries and on the reduction of the weight of the cars. The increase of efficiency of the motors, however, has been much neglected, especially from the material point-of-view.
The idea presented here in this paper is that both the soft magnetic material and the hard magnetic material need to be optimized at the same time [1]. For example, by using a better soft magnetic material, the losses are reduced, and also, less heat is generated. Thus, a magnet without Dysprosium can be used since optimized electric steels are used. The recent motors designed for electric vehicles can work at very high frequencies. In this case, resistivity of the magnets is an issue. Axial flux machines are in development nowadays. Some of the prototypes of axial flux machines use strontium ferrite magnets. One reason for the choice of ferrites is that the resistivity of ferrites is much lower than in the case of NdFeB or SmCo magnets.
The automotive industry is a mass production industry and requests cheap materials. Thus, there is pressure for avoiding expensive magnets which use Dysprosium or Terbium. Most of the manufacturers of electric motors, however, need magnets with high coercivity which is specified in the motor design. In these motors, irreversible reversal of magnetization of even parts of the grains of the magnets is a big problem, resulting in reduction of motor performance. This motivates the choice of high coercivity NdPrFeB type magnets. SmCoFeCuZr would have excellent performance, but the high cost of cobalt makes its use avoidable.
In this paper, we discuss how to model the losses in soft magnetic materials (electric steels) and also on the magnets. One relevant result of the modeling is that rotors with surface mounted magnets expose the magnet to high fields and strong eddy currents. Thus, buried magnets are a better option. Several types of magnet configurations have been tested as the V type used in the Toyota Prius and Tesla Model 3, the double V used in the GM Chevy Volt and the Delta type used by the Nissan Leaf. Many manufacturers have opted for the V type, but the concept used by BMW i3, the Hybrid Synchronous motors, is a possibility. The motor of the Tesla Model 3 makes use of the Halbach effect, and the benefits of using the Halbach array will be discussed. The Halbach array allows the soft magnetic material (the electrical steel) to be magnetized at the fields near the magnetic saturation.