Emerging Electric Motor Technologies for the EV Market
Apr 5, 2023
12 min readAdd to Favourite
Apr 5, 2023
12 min readAdd to Favourite
Electric vehicles (EVs) are a promising global strategy for decarbonizing the transportation sector. Tighter emission standards and improved batteries (in terms of lower cost and longer range) helped EVs gain traction.
The electric motor (the heart of an electric vehicle), along with batteries and power electronics, is one of the key components of an electric vehicle’s powertrain. Automotive OEMs are at the forefront of electric vehicles with the notion of sustainability.
The rapid growth of the electric vehicle market has created significant demand for electric motors for different types of vehicles, including the commercial/passenger vehicle segments, in different parts of the world. At the same time, the demand for electric motor parts and related materials is increasing.
FutureBridge delves into the different trends/developments in the field of electric motors for electric vehicles.
What drives the demand?
Concerning electric motors, the reduction of installation space, increasing power density, optimizing cooling concepts, and increasing controllability are key drivers for electric motor innovations. Reduction in reliance on rare earth metals also drives electric motor innovations. Innovations in enabling technologies like thermal management and power electronics are other drivers of motor innovations.
Unlike other industrial motors, the transmission system of a vehicle electric motor must not only be affected by the structural size of the vehicle but also meet operating conditions under complex conditions. High efficiency, lightweight, high power density, small size, reliability, and low cost are required for EV motors. In addition, the EV motor must adapt to the frequent starting, stopping, climbing, accelerating, and decelerating conditions of the vehicle. It requires a wide speed range and high overload factor for automotive geared motors to meet the performance requirements of high torque at low speeds or uphill or low torque at low speeds.
1. Axial Flux Motors
One of the key emerging motor types is the Axial flux motor which is gaining momentum in the electric vehicle sector. Axial flux motors have many EV design advantages over their radial flux counterparts. Magnetic flux is parallel to the axis of rotation in an axial flux motor (compared to perpendicular in radial flux machines). Axial flux motors provide substantially more power while having a lower weight density.
Although used for many years in stationary applications such as elevators and agricultural machinery, over the past decade many developers have improved the technology to make electric motorcycles, airport containers, delivery trucks, electric vehicles, and even aircraft.
Industry players viz. Mercedes has shown keen adoption with the investment and acquisition of YASA. It implies a greater interest in axial motors for automotive applications. Daimler will be using YASA for their motors in the upcoming AMG electric platform and Renault has partnered with WHYLOT to use axial flux motors in their hybrids starting in 2025.
Axial flux motors often have power densities above 6Kw/kg and still have good efficiencies.
With emerging e-mobility trends, the adoption and demand of Axial flux motors are expected to witness huge growth in coming years especially in high-performance vehicles and in applications where power density is critical.
Interesting development to look at Additive manufacturing player ExOne is working with Maxxwell Motors to develop a copper e-winding design for its axial flux electric motors that can be printed with metal binder jetting technology.
2. In-wheel Motors
One of the emerging electric motor configurations is the “INWHEEL MOTOR or Hub motor” with a direct drive mechanism. It can either be radial flux or axial flux motors. While a few companies have developed concepts that are marketed as IWMs, most include motors that are mounted far from the wheel (The Eco-move Q wheel, Nissan blade glider concept, etc.). Protean Electric, Elaphe, etc. are major propones of IWMs.
The modular approach of this system enables it to be retrofitted to any existing vehicle platform with no vehicle modifications (Some systems like the brakes have to be removed, but nothing needs to be modified).
Slovenia-based startup GEM motors have developed a patented modular multiphase technology to perfect its GEM motor. Its solution is at the forefront of the technology trend toward a fully integrated electric motor near the wheel. This technology simplifies the electrification of the vehicle and minimizes the number of parts while reducing weight and space.
Industry developments in ‘In-wheel-motor’ adoptions
3. Switched reluctance motors (SRMs)
Switched reluctance motors (SRMs) are coming up as an emerging alternative for e-mobility applications, with decades of reliability testing in zero-fault-tolerant applications, and no rare earth. Recent advances in power electronics and IoT are boosting SRMs to new, highly energy-efficient applications.
Some of the key developments in SRM technology include:
4. SynRM-IPM (PMaSynRM)
SynRM-IPM (PMaSynRM) has become another attractive electric motor type in the automotive industry for small electric vehicle segments. It outperforms other variants of traction motors in delivering higher torque with an increase in saliency due to air barriers and enhanced speed capability.
SynRM-IPM is a combination of an internal permanent magnet motor type and a synchronous reluctance motor rotor type that achieves more desirable characteristics in low-speed and high-speed high-efficiency EV applications. The advantages of adding PMs to the synchronous reluctance motor rotor construction are the increased motor power factor and thus reduced motor stator ohmic losses. The construction of SynRM-IPM involves placing small permanent magnets (often simpler ferrite ones) in some of these voids of SynRM to take advantage of both magnetic and reluctance torque while minimizing cost and the back EMF (or counter-electromotive force) high-speed inefficiencies that permanent-magnet motors suffer.
Tesla Model 3 features a SynRM-IPM motor. Tesla is not the first to use this type of motor, but its version is considered one of the best. Tesla’s specific innovation is the segmented magnets (four parts instead of the more typical single solid magnet). It helps to reduce the eddy currents and lowers the risk of magnets overheating. OEMs have been utilizing SynRM-IPM for hybrid and EVs.
The SynRM IPM technology is adopted for e-mobility applications by Tesla and Toyota and more. The use of high-efficiency and high-density motors is also spreading in traction, including the road ambit (from bicycles to heavy vehicles and operating machines), the railway/tramway sector, and the industrial one (forklifts and similar).
With new technologies, from 3D printing to in-wheel motors (IWMs) that allow a car to spin on the spot, electric motors could be grabbing more of the limelight. Electric motor improvements are pushing innovation in motor controls, thermal management, and other subsystems.
New Motor Topologies
FutureBridge has analyzed new motor topologies within the demanding electric motor ecosystem for other than Axial flux, SynRM-IPM, and SRMs.
Other emerging motor innovations are:
FutureBridge analysis also indicates the potential of SynRMs which are currently employed for industrial application to be utilized for traction application in near future.
Rare earth-free motors
Rare Earths is a major geopolitical issue with China in the epicenter. They are extremely destructive to the environment. For the most part, the vast majority of electric vehicles today with the most advanced electric propulsion technology need these very rare, very expensive, and environmentally destructive materials to achieve this high performance. – FutureBridge analysis anticipates greater demand for Switched Reluctance Motors and similar alternatives.
The Chinese counterparts in the EV ecosystem like BYD and Xpeng are proponents of Permanent Magnet Synchronous Motors wherein, NIO is advocating asynchronous permanent magnet motors (IMs).
Western automakers have adopted several strategies for reducing the rare earth metals in electric motors. Some, such as Toyota, still use permanent magnets but have reduced the use of rare-earth by developing magnet that requires 20-50% less neodymium. Others, such as BMW have made design changes. Its design reduces space and weight by integrating the engine, electronics, and transmission into one package.
Tesla’s S and X models have motors with and without rare earth magnets. Induction motors provide more power while permanent magnet motors are more efficient. Volkswagen also uses both types of engines in the new ID.4 crossover.
According to FutureBridge, Environmental and Supply challenges are the driving force for ‘Rare earth-free motor strategies by OEMs. OEMs such as Nissan and Honda have reduced or eliminated heavy rare earth elements such as dysprosium.
Despite the potential reduction in the use of materials such as neodymium per vehicle, the overall growth of the global electric vehicle market will lead to an overall increase in the demand for rare earth materials which would be an opportunity and threat at the same time.
Electric Motors and the associated ecosystem are set to play a critical role in achieving zero-emission propulsion and are poised for rapid growth over the next decade. It is expected that the electric motor will dramatically change in the next 8 to 10 years. It will be unrecognizable from what we see today, not in how it looks – but also in what it does.
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