For many of us today, the term ‘electric motor’ conjures up the image of an electric car, but electric motors play an essential role in thousands of other devices. In fact, there is hardly a piece of equipment used in the home that does not have an electric motor in it. But electromobility is, of course, the growth market with electric drive systems found not just in electric cars but also in e-bikes and e-scooters. Electric motors are also used to power drones – the unmanned aerial vehicles that will be playing an increasingly important role in logistics, emergency response and in the traffic and transport sector.
‘When we look for ways to make electric motors more efficient and more environmentally friendly, we tend to focus most of our attention on the battery. But the efficiency of an electric drive system can also be significantly enhanced by reducing losses in the motor itself,’ explains Ralf Busch, Professor of Metallic Materials at Saarland University. Professor Busch is one of the scientists now collaborating with partners in academia and industry to research a method of reducing core losses that could substantially boost the efficiency of an electric motor.
Matthias Nienhaus, Professor of Drive System Engineering at Saarland University, explains their strategy as follows: ‘During the energy conversion process in an electric motor, the magnetic field in the motor changes multiple times every second. Every time the magnetic field changes, there is a drop in efficiency, which cumulatively contributes to reduced overall motor efficiency. Put simply, the lower the losses, the more efficiently the motor can convert electric power into motion. For the all-important mobility sector, this means that the electric motor can power the vehicle for longer and thus increase its range.
The underlying problem is that the motor components that conduct the magnetic field have to be manufactured from iron-based alloys. Unfortunately, iron exhibits relatively high efficiency losses. Ralf Busch and his research colleague Isabella Gallino have come up with a potential solution involving amorphous iron alloys – a solution made possible thanks to recent developments in 3D printing. ‘Amorphous iron alloys are magnetically soft materials and so are easy to magnetize and demagnetize, that’s why they’re suitable as potential replacements for the ferromagnetic materials conventionally used for the cores of electromagnetic coils. The interesting aspect of using amorphous iron alloys is that the core losses are substantially lower.’ Amorphous metals – also known as metallic glasses – are melts that were cooled in a fraction of a second and were therefore unable to form the type of regular crystal lattice found when the melt is allowed to cool more slowly. The properties of these amorphous metals are drastically different to those of their crystalline counterparts, despite the fact that both have the same chemical composition.
‘If we can use amorphous iron alloys in electric motors, we could dramatically reduce core losses. That would represent a major step forward,’ says Matthias Nienhaus, who, together with his research assistant Chris May, plans to construct prototype electric motors from amorphous metal. This is where recent progress in 3D printing comes into play. ‘Around two years ago it became possible to process amorphous metals in 3D printers,’ explains Dr. Gallino, who successfully applied for funding for the project. Up until now, amorphous iron alloys for industrial applications have only been available in the form of very thin strips. At present, their most important application is in the anti-theft tags attached to retail articles. ‘Using novel printing methods, we have now been able to fabricate a larger workpiece made from amorphous iron – one that can be used as a soft magnet in an electric motor,’ explains Isabella Gallino. Expressed simply, the researchers aim to print out one thin strip of the amorphous material after another and then combine them to make a single larger component. If successful, this would immediately usher in the possibility of significantly reducing the core losses currently observed in electric motors.
But there is a huge amount of specialist know-how involved and what the research scientists in Saarbrücken are trying to do is not something that can be achieved with a standard 3D printer from a consumer electronics retailer. ‘Firstly, we – the material scientists – have to design the amorphous iron in such a way that the final component exhibits the required properties,’ says Dr. Gallino. ‘In the next stage of the process, our industrial partner Heraeus supplies the special powder for the 3D printer, which our partners in Sweden and Spain then print into a three-dimensional form using a special laser sintering process. Finally, the workpiece is examined in Italy to determine its magnetic properties. We do this in Italy because that’s where Europe’s top specialists for this type of analysis are located,’ says Gallino.
‘If everything goes well, the workpiece is then delivered to us here in Saarbrücken where we construct the prototype electric motor that we hope will display a much higher level of efficiency,’ explains Professor Matthias Nienhaus, who is the expert responsible for the motor fabrication process.
If the research project is a success, then the four years of basic research may well be followed by a period of technology transfer aimed at developing a marketable product. Although the research team are currently focusing predominantly on smaller motors, Ralf Busch already has one eye on the future: ‘Who knows where this could lead? Over the medium-term, our research could well contribute to a huge improvement in the driving range of electric vehicles.’ And that would be no small contribution to achieving a more sustainable world.