The MAHLE MCT Electric Motor for Cars and Commercial Vehicles Shines with Groundbreaking Advances: No Need for Rare Earths and Contactless Energy Transfer from Stator to Rotor.
Rare earths are metals that are not as rare worldwide as their name suggests. However, their extraction and processing are highly complex, often environmentally harmful, and lead to dependence on raw material imports, mainly from China. Therefore, eliminating rare earths offers advantages in manufacturing costs, sustainability, and supply capability.
This feat is achieved through the design of the MCT Electric Motor (MCT stands for Magnet-free Contactless Transmitter), which is a type of externally excited synchronous machine. In this design, the magnetic field required for operation is generated contactlessly through induction by exciter coils in the rotor. This technology does not require permanent magnets, thus avoiding the use of rare earth elements like neodymium, which are components of magnet alloys.
The contactless energy transfer makes the MCT Electric Motor wear-free, as unlike traditional externally excited synchronous machines, the rotor current is transmitted without mechanical friction. This results in significant advantages: a higher possible speed level and a compact design due to the absence of the slip ring-brush system.
The unit operates across a broad performance range and is especially energy-efficient at high speeds. These features mark a significant advancement by MAHLE in this type of motor construction. At operation points relevant for everyday use, the energy transfer into the MCT rotor achieves excellent efficiency, contributing to minimal overall energy consumption of the externally excited synchronous machine.
Since the unit is maintenance-free, it is suitable for a wide range of applications. In e-mobility, the MCT Electric Motor, with its compact design and scalability, can be used in everything from small cars to heavy commercial vehicles. Its durability makes it an ideal long-term performer.
In electric motors, increased power demand generates more heat in the system. Current electric motors, therefore, only deliver peak performance for a short time and require a reduction to about 40 to 60 percent of their peak power in continuous operation to avoid critical component temperatures that could significantly shorten product life or cause damage. The cooling concepts of current electric traction motors are mostly based on a water-glycol mixture circulated around the stator. The primary goal of cooling is to maximize the ratio of continuous to peak torque.
To make progress in this area, MAHLE has developed SCT Technology (Superior Continuous Torque) for permanently excited drive motors. The direct oil cooling concept enables a class-leading torque ratio and a significantly more durable and lighter electric traction motor. The cooling system's oil is drawn into the rotor and spreads in its hollow shaft to cool the permanent magnets. Then, the oil flows around the right stator winding head and is circulated multiple times to enhance cooling. Afterward, the oil is directed to the left side of the motor, where it also circulates around the end winding, absorbs the heat generated there, and is removed from the motor. As this concept minimizes drag losses, the highest efficiency levels are achievable. The waste heat from the coolant can be used to temper the batteries or the vehicle.
The oil cooling of MCT Electric Motors significantly reduces the motor's size and mass compared to water jacket cooling technology. Material savings and increased efficiency also indirectly lead to positive environmental effects, as CO2 emissions can be minimized both in the manufacturing and usage phases of the product.