EV Innovation

Much needed electric motor and inverter technology innovations – 2022

The transition from silicon insulated gate bipolar transistors (Si-IGBT) to silicon carbide (SiC) metal oxide semiconductor field-effect transistors is an important development trend for inverters (MOSFET). The advantages of SiC technology are immediately apparent in the low power range, which is the most common operating mode in ordinary driving. Even further optimisations can be accomplished using sophisticated control methods such as variable switching frequency and discontinuous modulation. Higher switching rates that result in significant voltage gradients, on the other hand, make electromagnetic interference and isolation more difficult.

Other notable design advancements include the incorporation of cooling structures directly into the direct bonded copper (DBC) substrate, as well as increased power module integration and modularity. Meanwhile, three-level gallium nitride (GaN) technology deployment on DC-DC converters and traction inverters, two-level SiC with sophisticated gate drivers or soft switching technology, and current source inverters with dual blocking devices are all possibilities.

In Electronic Driver Unit (EDU), the electric motor is the primary source of loss. The efficiency of electric motors must be optimized in order to increase the vehicle’s driving range. It is beneficial to have a clear distinction between prime movers and secondary axles when using traction drives. While prime movers must be efficient over the whole working range, secondary axles are more concerned with reducing cost and drag losses. Externally excited synchronous machines (EESM) and induction machines (IM) are the primary motor technologies for secondary axles due to lower drag losses. The prime mover market is characterized by a wide range of motor topologies.

Because torque is proportional to volume, faster speeds may be attained with the same quantity of raw materials, resulting in increased e-motor power with the same amount of raw materials—a noticeable gain for the environment. The loss density of high-speed motors is a significant drawback. Cooling becomes much more necessary as more power is concentrated in a tiny space, resulting in larger losses.

Coolant can be administered directly to the active portions of the electric motor using oil cooling. As a result, cooling options such as a water jacket, stator oil cooling channels, shaft cooling, spray ring cooling, and rotor spray cooling are available to manufacturers. Understanding the benefits and drawbacks of various technologies, as well as the application case itself, will be critical to the success of high-speed electric motors with high continuous power ratings.

As the speed range of the electric machine increases, single-speed gearboxes are suitable for the bulk of passenger automobile applications. EDUs with multi-speed gearboxes are required for heavy-duty vehicles. This is owing to the wide gap between the required vehicle launch capability and the maximum speed. To fulfil the vehicle’s constant torque needs, the bulk of these applications require to powershift gearboxes.

Locking mechanisms are also becoming required to use park-by-wire technology. Other vehicle uses employ vehicle braking systems, while some electric drives include transmission-side parking locks. A permanent electric powertrain and a temporary electric drive unit are both employed in all-wheel drive applications. Disconnecting mechanisms are installed in these temporary units to allow the operation of electric machines with higher drag torque. A smooth yet quick re-engagement is required here.

When it comes to next-generation e-motor and inverter technology development, there’s so much to innovate to keep the industry growing.

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