Project Seeks to Optimize Composition of Magnets for Traction Motors to Improve Economic Competitiveness
A research project currently underway at St. Pölten University of Applied Sciences (Austria), in cooperation with the University of Sheffield (UK), is exploring the ideal composition and structure for high-performance permanent magnets intended for use in hybrid and electric car motors—specifically, how the proportion of dysprosium can be reduced without compromising the thermal stability of the magnets. By optimizing magnets, the researchers suggest, hybrid and electric cars can be made economically competitive.
Overall, an electric or hybrid drive contains around 2 kg (4.4 lbs) of magnetic material in their motors. At present, neodymium iron boron magnets form the basis of this. These have considerably less mass than conventional magnets, but deliver the same level of performance. In order to ensure the magnetic properties are retained even at high temperatures—such as those that occur within a car—the rare earth element neodymium is partially replaced by dysprosium, another rare earth element. This increases the coercive force of the magnet—its stability against demagnetization. However, notes Prof. Thomas Schrefl, project leader:
Compared to neodymium, the proportion of dysprosium in the ore is less than 10 percent. However, the high-performance permanent magnets currently used for hybrid and electric cars contain up to 30 percent dysprosium. In the long term, this will prove problematic when it comes to raw materials, particularly if you consider that, in just a few years, all new cars will be fitted with a hybrid or electric drive.—Prof. Schrefl
The research project is applying computer simulation to examine how the chemical composition and structure of a magnet influences its performance. This information will then be used to identify ways to optimize the magnetic material so that it requires fewer expensive raw materials, yet continues to deliver the best possible performance.
Applied in conjunction with the finite element method, simulation is helping to reveal the internal workings of a magnet. The computer is used to break down complex structures into individual elements so that they can be evaluated.
We reconstruct the magnet on the computer and break the granular structure of the magnet down into finite elements. By breaking down the microstructure into millions of tetrahedrons and prisms, we can recreate the spatial distribution of the metallic phases within the magnet in a computer model. We can then use the computer to simulate the effect that changes in the proportion of dysprosium have on the coercive force of the magnet.—Prof. Schrefl
The finite element method has already been applied in the automotive industry for carrying out computer-based crash tests and wind tunnel tests.