An EV Drive Unit Built Without Rare Earth Minerals
In this article, I want to share news from Vitesco Technologies about a really cool EV drive unit design the company produced. What really sets it apart from other designs is that it doesn’t depend on rare earth minerals and permanent magnets. For those unfamiliar, let’s take a quick look at what these minerals are so that we can better appreciate not needing them. After that, I’ll go through what Vitesco Technologies is doing and how it has some efficiency advantages, too.
What Are Rare Earth Minerals?
Rare earth minerals, also known as rare earth elements (REEs), are a group of 17 chemically similar metallic elements found within the Earth’s crust. These elements include scandium (Sc), yttrium (Y), and the 15 lanthanide elements (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). Despite their name, these elements are not actually rare in terms of their abundance. They are called “rare earth” because they were originally discovered in rare minerals and were initially thought to be quite scarce.
Rare earth minerals are essential components in many modern technological applications, including electronics, renewable energy, aerospace, defense, and medical industries. They possess unique magnetic, catalytic, and luminescent properties that make them indispensable in various high-tech devices and systems, such as smartphones, electric vehicles, wind turbines, and missile guidance systems.
The extraction and processing of rare earth minerals are challenging due to their geochemical properties. These elements often occur together in the same mineral deposits, and their similar chemical characteristics make it difficult to separate them from one another. Consequently, the mining and refining processes for rare earth minerals are complex, time-consuming, and expensive, which contributes to their limited supply and high market value.
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The global production and distribution of rare earth minerals are concentrated in a few countries, with China being the largest producer and exporter. This has led to concerns over the security of the supply chain, particularly for countries dependent on these critical resources for their core industries, as China has used its rare earth supply to exert pressure on its neighbors in disputes. In recent years, efforts have been made to explore new sources of rare earth minerals and develop alternative technologies that can reduce dependency on them.
Environmental and social concerns also surround the extraction and processing of rare earth minerals, as these activities can have significant negative impacts on local ecosystems and communities. The mining process often produces toxic byproducts and radioactive waste, which can contaminate water, soil, and air if not managed properly. Furthermore, the exploitation of rare earth resources has been linked to human rights abuses, such as forced labor and unsafe working conditions in some countries.
Avoiding Their Use In Drive Units
For all of these reasons, it’s best to avoid using the minerals whenever possible. This lowers cost, environmental impact, and vulnerability to international resource politics. It also leaves more of them available for important applications, like medical imaging. So, it’s great news that a technology company figured out how to build an EV drive unit — the motor, reduction gear(s) and differential — that doesn’t depend on them!
Vitesco’s Life Cycle Engineering effort has led to the expansion of the fourth generation of the fully integrated electric axle drive platform (EMR4, Electronics Motor Reducer) by introducing a new option that enhances its life cycle assessment. The platform development now includes a new rotor without permanent magnets at its core, which constitutes an externally excited synchronous machine (EESM) that operates without the need for rare earths. Consequently, this innovation lowers the rotor’s cost and eliminates the carbon footprint associated with the mining and processing of these ores, along with all of the other advantages you’d expect after reading the last section.
“Top results in the sustainability and efficiency of electric cars will be achieved, if the vehicle drive is optimally adjusted to the specific scenario,” said Thomas Stierle, division head of Vitesco Technologies’ Electrification Solutions. “The externally excited rotor without permanent magnets is a particularly sustainable option for our customers. The higher the performance requirements to the drive, the more economically attractive EESM technology becomes.”
Until recently, the majority of electrified vehicles utilized permanent magnet synchronous motors (PSMs) in their synchronous machines, which were considered efficient and generally easier to produce than externally excited machines. These machines generate magnetic fields using coils in the rotor. Vitesco Technologies has successfully overcome significant challenges in designing externally excited machines by leveraging years of experience from series applications and implementing targeted design modifications.
This has enabled them to achieve the same performance class with both PSM and EESM technologies while utilizing the existing space in the platform design for both options. Employing an advanced winding technique, the innovative EESM rotor becomes a cost-effective choice within the latest drive platform. Particularly when high-performance demands require a large magnet mass in a PSM, EESM machines prove to be more affordable and sustainable.
Besides the cost savings from eliminating permanent magnets and enhanced sustainability, this type of machine provides additional benefits. As Rösel explained, when a vehicle operates efficiently in “sailing” mode, the externally excited machine conserves one watt-hour of electricity per kilometer due to the absence of drag from a permanent magnet field in the rotor. This reduction in drag lowers the drive’s power requirement by up to five percent, all without necessitating a mechanical decoupling device.
The company is also working on several other exciting projects that it showed off at a trade show in April. These include a battery management system (BMS) that bolsters safety, battery longevity, and efficient charging. The “Battery Pressure Sensor” further enhances safety by detecting gas emissions within the battery module. Additionally, Vitesco Technologies’ “Thermal Management Module” ensures that all connected sub-systems of the drive operate within their optimal temperature range, promoting maximum efficiency.
The company also showed its commitment to vehicles smaller than cars, showcasing a demo version of its 48-volt system designed for smaller electric two-wheelers. The system comprises an eDCU (Electric Drive Control Unit) and a compact, powerful electric motor equipped with a unique inductive rotor position sensor. This system is currently under development for series application in collaboration with customer projects.
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