In an electric vehicle (EV), the e-propulsion architecture converts stored electrical energy into mechanical motion through a coordinated network of power-electronics, electric machines, and drivetrain components.
Increasingly, automakers are moving from discrete motor, inverter, and gearbox assemblies toward fully integrated e-propulsion systems, often referred to as electric drive units (EDUs). This shift is driven by higher voltage architectures, efficiency demands, and packaging constraints.
A fully integrated e-propulsion system entails more than an electric motor, encompassing the inverter, gearbox, control electronics, and thermal subsystems that regulate power flow, torque, and efficiency across a wide range of operating conditions.
Figure 1. An integrated electric axle drive showing the inverter, motor, gearbox, and differential within a single housing. Compact layouts like this reduce cabling losses and improve thermal coordination in modern EV propulsion systems. (Image: ResearchGate)
By unifying these elements, manufacturers can reduce weight and cabling losses while improving thermal coordination, manufacturing scalability, and overall drivetrain efficiency.
System architecture
Recent benchmarking confirms the growing shift toward integrated e-propulsion architectures. A 2025 study by Drexler et al. analyzed 48 traction drive units from 31 vehicles built between 2018 and 2023 and found that roughly half feature a motor–gearbox–power-electronics integrated topology, underscoring what the authors call “a clear trend toward compact and unified drive systems.”
This consolidation aligns with OEM roadmaps that increasingly favor modular e-axles for both passenger and commercial EV platforms. Integration allows shared cooling loops, simplified wiring, and tighter coordination between electrical and mechanical subsystems, all of which enhance efficiency and power density.
To understand how these elements interact within the propulsion chain, it helps to trace the energy flow through the system. Electrical energy from the traction battery passes through a dc link to an inverter, which switches high-voltage dc into controlled three-phase ac to drive the motor. The resulting mechanical torque then transfers through a single- or multi-stage reduction gearbox and differential assembly to the wheels.
Additionally, the motor control unit (MCU) and vehicle control unit (VCU) manage torque requests, regenerative braking, and protection functions in real time, maintaining a closed feedback loop between driver input and drivetrain response. The industry’s transition toward 800-V system architectures and SiC-based inverters, which use silicon carbide (SiC) power semiconductors to reduce switching losses and improve efficiency, has further accelerated this integration trend.
These technologies lower current for a given power level, enabling thinner cabling, smaller passive components, and shared cooling paths between the inverter and motor. As switching speeds and power density rise, electrical, thermal, and mechanical domains must now be co-designed to maintain stability, electromagnetic compatibility, and long-term reliability.
Design considerations and engineering challenges
Thermal management remains a defining constraint. Power semiconductors and motor windings generate concentrated heat during acceleration and regenerative events, requiring liquid-cooling loops that balance flow between the inverter and motor. Uneven cooling or poor loop design can introduce thermal gradients that accelerate insulation breakdown and bearing wear.
Packaging and noise-vibration-harshness (NVH) considerations also become more critical with integration. Combining the inverter, motor, and gearbox into a single drive unit minimizes cable losses and improves response time but concentrates multiple heat sources and vibration paths within one enclosure.
Achieving durability under these conditions demands careful thermal zoning, electromagnetic shielding, and sealing strategies that account for vibration, pressure differentials, and long-term environmental exposure.
At the same time, the same integration that improves performance also increases system interdependence. A fault in the inverter may require replacement of the entire drive unit, while shared coolant circuits can propagate localized overheating. NVH management becomes more complex as rotating components, gear assemblies, and high-frequency power electronics operate within the same enclosure.
In contrast, discrete architectures with separate motor, inverter, and gearbox offer greater serviceability and supplier flexibility but introduce higher wiring complexity, greater packaging volume, and additional cooling interfaces.
For heavy-duty and fleet applications prioritizing uptime and maintainability, this modular approach can remain advantageous despite lower power-density gains.
Benefits of integrated architectures
When properly engineered, integrated drive systems deliver several measurable advantages. Compact packaging and shared cooling allow designers to optimize electrical and thermal performance, while tighter mechanical coupling improves dynamic response.
- Higher power density and reduced losses due to shorter conductor paths
- Improved thermal coordination through shared coolant circuits
- Simplified vehicle integration from reduced volume and fewer interfaces
- Enhanced dynamic control, enabling advanced traction and torque-vectoring strategies
These characteristics are especially effective in multi-motor EV platforms, where independent front and rear drive units can dynamically distribute torque and maximize regenerative-braking efficiency.
According to the National Renewable Energy Laboratory (NREL), “Integration of power electronics into the electric motor achieves higher power densities of the electric traction drive systems, enabling volume, mass, and cost savings on their enclosures, interconnections, and cooling systems and overall number of required parts. As a result, the electric vehicle propulsion system is lighter, more compact, and more efficient.” (NREL, Integrated Electric Traction Drive Research, 2024 | Figure 2)
Figure 2. Integration concepts for electric traction drives: (a) separate power electronics enclosure attached to the motor case, (b) power electronics distributed or mounted radially on the motor casing, and (c) power electronics integrated axially in the motor front or back plate. (Image: NREL)
Industry adoption
Recent announcements from major Tier-1 suppliers highlight how integration of electric drive components is advancing from research into full production for EV platforms.
- Magna International – Announced a contract to supply a specialized eDrive system for a North America-based OEM’s BEV platform. The system integrates two e-motors, two inverters, and two gearboxes within a single 800-V drive package that delivers 726 kW and 8,000 Nm of torque (Figure 3). The design improves packaging efficiency, thermal coordination, and overall system performance in high-power battery-electric applications.
Figure 3. This specialized eDrive system can deliver 726 kW of power, 8,000 Nm of torque to a high-end niche vehicle platform. (Image: Magna International)
- Schaeffler AG – Introduced the EMR4 electric axle drive, a scalable e-axle system for EVs that “combines a permanent-magnet synchronous motor, power electronics, and transmission in a single compact housing,” according to the company. “Its modular architecture allows for precise adaptation to a wide variety of vehicle concepts” (Figure 4). It offers up to 96% efficiency and supports modular configurations for different power classes and vehicle segments. A variant that operates without rare-earth magnets is also available.
Figure 4. EMR4 e-axle integrates the motor, power electronics, and transmission in a single compact housing for high-efficiency EV drivetrains. (Image: Schaeffler AG)
- ZF Friedrichshafen AG – Offers a family of scalable electric drive systems that combine the motor, inverter, transmission, and control software into configurable architectures. The SELECT eDrive platform supports 400 and 800-V systems using silicon or silicon-carbide power modules and achieves average WLTC efficiencies above 93% for primary drives (Figure 5). According to the company, flexibility and standard are combined: “em:SELECT offers an application-specific standardized stator concept, as well as standardized optimized rotors depending on the technology.” The modular platform allows OEMs to tailor integration depth and motor technology, whether asynchronous, permanent-magnet, or separately excited synchronous, to match application requirements.
Figure 5. This modular eDrive system integrates the electric motor, inverter, and transmission within a single housing, supporting 400 and 800-volt architectures. (Image: ZF Friedrichshafen AG)
- BorgWarner – Announced a 7-in-1 Integrated Drive Module (iDM) exclusively designed for a customer’s hybrid SUV. The system consolidates multiple functions, including “two electric motors featuring the company’s patented high-voltage hairpin winding technology, a dual inverter integrated with onboard charger (OBC), dc-dc converter, battery voltage boost, vehicle control unit (VCU), and power distribution unit (PDU) functions, as well as an eGear transmission — all within a single compact unit.” It’s scheduled for mass production in 2026.
Together, these systems demonstrate how integration of motors, inverters, and transmissions into unified drive units is becoming a standard approach for modern EVs, improving power density and simplifying vehicle assembly.
Conclusion
The shift toward integrated e-propulsion systems represents a defining evolution in EV drivetrain design. Consolidating motors, inverters, and gearboxes into unified assemblies delivers clear benefits in power density, thermal performance, and packaging efficiency while supporting the transition to high-voltage architectures.
However, as integration increases, so does the need for cross-domain collaboration between electrical, mechanical, and thermal engineers to ensure reliability, manufacturability, and serviceability.
References
- D. Drexler et al., “Advances in electric motors: A review and benchmarking of product design and manufacturing technologies,” e & i Elektrotechnik und Informationstechnik, 2025. [Online]. Available: ResearchGate
- ResearchGate, “Exemplary axle drive designs in offset and concentric configurations.” [Online]. Available: ResearchGate
- National Renewable Energy Laboratory (NREL), Integrated Electric Traction Drive Research, 2024. [Online]. Available: NREL
- Magna International, “Magna awarded specialized eDrive system business with North America-based OEM,” News & Press Release, 2024. [Online]. Available: Magna.com
- Schaeffler AG, “Schaeffler presents fourth-generation electric axle drive (EMR4),” Press Release, 2024. [Online]. Available: Schaeffler.com
- ZF Friedrichshafen AG, “ZF SELECT eDrive platform for 400 and 800-V electric propulsion systems,” Product Brief, 2025. [Online]. Available: ZF.com
- BorgWarner Inc., “BorgWarner to supply leading Chinese OEM with 7-in-1 Integrated Drive Module,” Press Release, Oct 30, 2025. [Online]. Available: BorgWarner.com
Filed Under: Electric Motor, Electrification, FAQs, Vehicle Control Unit