Advanced Electric Machines (AEM) has presented what qualifies as the most sustainable electric motor in the world since it is completely free of permanent magnets composed of rare earths. The HDSRM and SSRD engines maintain and even exceed the performance and efficiency of electric motors that need permanent magnets, but eliminate all their environmental drawbacks. The company has already completed the development of both engines, intended for commercial electric vehicles and electric passenger cars, and is now seeking financing for its large-scale production.
A synchronous electric motor It generally incorporates permanent magnets composed of rare earths such as dysprosium, gadolinium or neodymium. These magnets provide a magnetic flux when magnetized by another magnetic field and do not lose their properties once the cause of the magnetism ceases. Embedded in the rotor of the motor, they eliminate the need to implement an external excitation system, and brushes, necessary to generate the corresponding magnetic field in the rotor and make it rotate when exposed to the field generated externally in the stator.
Rare earths and the environment
According to an independent research study, each ton of rare earth material extracted from the ground generates up to 1.4 tonnes of radioactive waste, 200 m3 of wastewater containing acid, 60,000 m3 of off-gas containing hydrochloric acid and 27.6 tons of CO2. Based on a world automobile production of 97 million vehicles, AEM’s technology could save the emission of 133 million tons of CO2annually into the atmosphere and avoid the accumulation 300,000 tons of radioactive waste.
Rare earths and supply
For most countries, rare earths also appear as one of the critical and long-term worrying materials in terms of security of supply. The result of this uncertainty is that, for example, the price of neodymium, which is commonly used in permanent magnet electric motors, has increased by more than 240% between March 2020 and March 2021. These trends make rare earths financially unsustainable and environmentally problematic materials.
Recycling of motors
In addition to rare earth metals, traditional permanent magnet motors also use copper windings. At the end of its useful life, copper must be removed from motor before recycling, but the presence of permanent magnets, which must be separated by special procedures, makes the process difficult and expensive. AEM claims that its technologies can be produced using only steel and aluminum, which means it can be quickly, cost-effectively and completely recycled.
The two AEM electric motors
Unlike today’s standard electric motors, AEM has created two electric motors called HDSRM and SSRD, totally free of magnets formed by rare earths such as neodymium or dysprosium. In order to eliminate them completely, AEM proposes the use of switched reluctance motors (SRM) in which the rotor is made of electromagnetic material but is not a permanent magnet.
The reluctancia is the resistance of a material to the passage of a magnetic flux when it is influenced by a magnetic field. Unlike common motors that require external excitation to create the magnetic fields, the energy is sent to the stator windings rather than the rotor. This greatly simplifies the mechanical design since the energy does not have to be delivered to a moving part, but it complicates the electrical design since it is necessary to use some type of switching system to deliver energy to the different windings.
The development of both engines is completely finished. The company is in the financing search phase with the intention of implementing the assembly lines for its serial production. AEM works closely with different organizations in the UK, the US and Europe to achieve this goal. The facilities that can manufacture them can produce 12,000 engines per year to meet short-term demand. It is also working to implement global expansion plans that meet the longer-term requirements of its customers.
HDSRM, the electric motor for commercial electric vehicles
HDSRM is an SRM engine that runs on standard power electronics used by most electric vehicle drivetrains. Its design and technologies, both patented, differ from the SRMs that the industry offered until now, since it can run silently and with minimal torque fluctuation, the main drawback of this technology.
The company assures that from the initial stage, in the still conceptual phase, they have been able to demonstrate that HDSRM equals the performance of the best permanent magnet motor of the same size by adding a greater efficiency. In addition, the robustness of its construction avoids the risk of demagnetization due to overheating and ensures the ability to free run without electromagnetic losses. Two features that allow a greater range and lower costs in the transmission system compared to other alternatives.
HDSRM has been specifically developed for use in commercial vehicles, which require very high levels of continuous performance and long service life. It has been designed as a modular solution, so it is possible to scale to higher levels of power and torque, or combine several HDSRMs to make the output more flexible according to the particular needs, allowing an even wider maximum efficiency zone.
HDSRM can also be combine with internal combustion engines that act as a traction motor or generator for hybrid solutions. AEM offers transmissions for these cases that can link the output of up to three HDSRM motors, reaching a maximum torque of 4200 Nm. Furthermore, it provides tailor-made gearboxes with ratios adapted to the application of each vehicle.
AEM currently offers HDSRM in three different settings. In its standard form, the HDSRM300 offers power up to 214 kW (287 CV) and a maximum torque of 380 Nm. With less power, 166 kW (221 CV), the HDSRM300T increases torque to 520 Nm. Both engines weigh 75 kg and are liquid-cooled. Finally, the smaller, air-cooled HDSRM150C weighs just 25 kg and offers a maximum power of 50 kW (67 CV) and a maximum torque of 100 Nm.
SSRD, the electric motor for electric passenger vehicles
The second of the electric motors is the SSRD, which according to AEM “takes this technology to the next level, delivering performance benefits that meet industry goals for 2035.” It is designed for high volume applications. Can deliver 50% more power with 35% less weight compared to permanent magnet motors used in electric passenger vehicles. The flexibility of its technology allows it to offer power densities ten times higher than these, reaching up to 29 kW per liter.
The SSRD has been developed and patented for use specifically in electric passenger cars. It allows a power delivery that goes from 125 kW (168 CV) with a single motor up to 600 kW (805 CV) operating as an electric axis. The production of the SSRD is extremely profitable, since the list of materials that comprise it is much shorter than that of a permanent magnet motor. Others, add aa 10% efficiency improvement and 100% recyclability.