The future of integrated drive modules

Online Editor

Explore the conceptualisation and development of next-gen drive modules, pushing technological advancement to new heights.

The next-generation drive module responds to market demands for ultra-compact systems aimed at reducing costs and offering higher efficiency than traditional systems. The fully integrated high-speed drive module is equipped with a high-speed differential gearbox at the rotor shaft of the electric motor, as well as two gearboxes for low torques. By integrating a differential unit with lower torque capacity, the required space compared to similar concepts has been significantly reduced.

Due to system requirements, the electric motor has been completely redesigned compared to currently produced motors. Taking these requirements into account, new rotor properties have been developed, allowing speeds of over 20,000rpm. Despite further reduction in rotor losses, such a concept requires additional optimisation of motor cooling. The solution involves complete immersion cooling of the stator winding heads in circulating oil flow.

E-motors: High-voltage hairpin technology

Hairpin technology for electric motors has achieved a power density and maximum efficiency of over 97% with the latest hairpin stator winding technology (HVH) for the high-voltage range. The motors in the HVH series are available in multiple versions with various configurations of different lengths, cooling methods, and winding options, either as a complete motor with housing or as a rotor-stator unit. The product portfolio starts with an outer diameter of 146mm (HVH146) and a peak power of 90kW. The medium-size and power range are covered by several variants of the HVH180 with peak powers up to 190kW. For applications requiring higher power, BorgWarner offers several versions of the HVH220 with a peak power of 350kW.

At the top end of the product range for passenger car applications is the high-performance version with an outer diameter of 264mm (HVH264) and a peak power of 450kW. Especially in the high-power versions, regulated oil cooling is used for the rotor, where the cooling medium is brought close to the permanent magnets. This proximity to the magnets is crucial for continuous power and also allows the use of magnets with lower rare earth element requirements.

The HVH320 is a novel development for applications requiring high torque at low speeds. This new HVH320 platform, launching in 2024, will be produced in three versions with maximum power/maximum torque of 1,280Nm/485kW, 1,500Nm/525kW, and 1,650Nm/575kW. The motor features innovative wire insulation (single-layer polyether ether ketone) meeting the highest quality standards, as well as immersion cooling of the winding heads to deliver the highest possible continuous torque. Fully bonded laminated core packages in the stator and rotor ensure high efficiency. The end winding and stator are designed to provide sealing against a thermal protection cover that directs oil flow.

In motors with interior permanent magnets (IPM), neodymium permanent magnets are used in the current large series with a low proportion of heavy rare earth elements dysprosium or terbium. The next development focuses on a concept that aims for sustainability without heavy rare earth elements. Since heavy rare earth elements protect against demagnetisation under extreme operating conditions, new magnet techniques, further improvements in stator and rotor cooling, and optimisation of motor control, which can limit the current peaks when switching to active short circuit (AKS), are combined in a holistic approach.

S-winding technology

The second generation (S-Wind Gen2) is widely employed in P2 drive modules for hybrid vehicles in the EU and Chinese markets, with an outer diameter of 270mm (SW270). The latest generation (S-Wind Gen3) is utilised in 48-V P3 modules with an outer diameter of 130mm (SW130) for drive motors.

Compared to hairpin technology, S-winding offers clear packaging advantages due to the length of the winding head, eliminating the need to weld individual pins. This is particularly crucial for P2 module applications. The S-winding technology is based on a stator geometry with open stator slots. A special winding process enables the extension of the formed continuous wire initially wound onto a mandrel into the stator. According to measurements conducted in accordance with the Worldwide Harmonised Light-Duty Vehicles Test Procedure (WLTP), the efficiencies of both concepts differ by 0.8% when using a comparable number of slots and conductors per slot.

With the further development of S-winding technology, variants with a higher number of conductors per stator slot and a higher number of stator slots are being developed. This enables consistently high rotational speeds, and with an identical stator diameter, the same efficiency as hairpin technology is achieved according to WLTP. This approach allows for better efficiency than hairpin technology at high torque and high rotational speeds (typical during highway driving) due to significantly lower alternating current copper losses with slightly higher direct current copper losses due to the smaller wire cross-section in conjunction with the large number of wires per slot.

 

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