Efficiency is the name of the game

The widespread adoption of battery electric vehicles (BEVs) hinges on efficiency, a factor that influences charging speed, battery range, and overall performance. In fact, according to a 2024 survey by ABB Research, 91% of 2,400 global businesses stated that energy efficiency critically influences their choice of electric motors¹. However, efficiency extends beyond battery advancements. Optimizing BEV powertrains through high-voltage systems and advanced winding wire solutions plays a crucial role in reducing energy losses and improving drivetrain performance. In this blog, we will explore how high-voltage systems and advanced winding wire solutions contribute to enhancing electric drivetrain performance.

As vehicle manufacturers aim to maximize range while minimizing cost and weight, system efficiency has become a decisive factor in electric motor design. This is commonly measured by power consumption per mile driven. At the moment of writing, EVs such as the Hyundai[VV1] Ioniq 6 (800V) and Lucid Air Pure (900V) excel in this category, each consuming about 0.24 kWh per mile driven (according to WLTP cycle).

But if we zoom in on the electric drivetrains, we would have to define efficiency by how much electrical energy gets effectively converted into mechanical power at the wheels. The correlated energy losses occur at different stages, primarily within the inverter – which converts DC to AC –, and the electric motor – which transforms electrical power into mechanical motion. Based on this information, two key levels of efficiency assessment emerge:

• Overall system architecture. This includes battery voltage, inverter efficiency, and positioning of subcomponents.
• Component-level efficiency. How do we minimize losses in critical parts of the drivetrain, such as the inverter and electric motor, during power transmission?

In recent years, extensive research has been conducted on the role of the overall system architecture in improving overall cost efficiency. Higher voltage systems offer several key advantages, including faster charging speeds, reduced cable size and weight, and lower power losses. Secondly, because the EV battery accounts for the largest share of an electric drivetrain’s cost, optimizing its energy efficiency is vital. One of the most effective ways to do so, is to increase the system voltage while maintaining the current to avoid additional power losses. Typically, two primary voltage classes are distinguished:

• Standard 400V Class – Found in most BEVs on the road today, with system voltages ranging from 250V to approximately 500V.
• New 800V Class – Includes systems operating above 600V, with some exceeding 900V (e.g., Nio’s latest generation at 925V).

Even though an increasing number of OEMs are introducing higher-voltage EVs and dedicated production platforms, there remains uncertainty in quantifying the total cost of ownership (TCO) benefits. Various studies suggest that, under ideal conditions, 800V systems could increase the EV range by up to 15% and improve overall efficiency by around 10%. Based on a 2024 lithium battery price of USD 115/kWh, this would translate to a financial gain of over USD 1,000 for large battery packs.

Additionally, maximizing drivetrain efficiency requires minimizing power losses, particularly in the motor (such as harmonic losses) and inverter (such as switching losses), which constitute the majority of electrical energy losses. A higher system voltage enables the optimization of these losses, provided that appropriate technologies are implemented—such as silicon carbide (SiC) semiconductors in inverters³, which significantly enhance efficiency and performance. Real-world examples include the new BMW i5, which features an improved drivetrain, including a SiC inverter, and demonstrates an efficiency gain of 8-9%⁴.

5-10% WLTP range improvement¹³

200-mile WLTP (50kWh battery) improves up to 220 miles (800V, SiC inverters, lower current in system

The inverter plays a crucial role in maximizing the efficiency benefits of 800V architectures. By leveraging new semiconductor materials like Silicon Carbide (SiC) and Gallium Nitride (GaN), conduction losses are significantly reduced, while higher switching frequencies further enhance motor efficiency by minimizing harmonic losses.

Recent studies estimate that advanced inverter technology can contribute to efficiency gains of up to 8%, driven by:

• SiC conductivity improvements³: +3%
• Reduced switching losses (improved slew rate): +2-4%
• Higher switching frequencies: +1-2%

By implementing SiC-based inverters, OEMs can improve overall drivetrain efficiency, leading to greater range, lower energy consumption, and enhanced power output in high-voltage EV systems.

A quick search reveals a vast range of electric motor technologies, yet permanent magnet synchronous motors (PMSMs) continue to dominate the market. PMSMs are projected to represent 78% of the market by 2035⁶, despite growing interest in externally excited synchronous motors (EESMs), induction motors (IMs), and axial flux motors. These alternatives do, however, have lower adoption rates due to cost-efficiency trade-offs and challenges during production or when in use.

When evaluating existing EV models (which have designed years ago), we observe average efficiency ratings close to 90%⁷, with nearly all utilizing permanent magnet technology.

For high-speed motors, choosing PMSMs over EESMs and IMs can enhance efficiency by 2-5%. Moreover, Silicon Carbide (SiC) inverters further boost efficiency, contributing 3-4% improvements, with SiC inverters expected to become the standard in over 50% of EVs by 2028.

Today’s state-of-the-art electric motors have achieved significant efficiency gains across both PMSMs and EESMs¹⁴. The table below presents WLTP efficiency figures for recent e-motors, showcasing how modern technology—such as advanced winding wire solutions—has optimized performance, with peak efficiencies surpassing 95%.

However, there is still room for improvement, as average efficiency levels remain lower, particularly in real-world driving conditions such as city traffic and constant-speed highway travel.  

Motor efficiency is influenced by power losses occurring during energy conversion — from electrical into magnetic and down to mechanical in the end. Compared to inverters, total e-motor losses are 3-4 times lower, but load conditions significantly impact loss distribution:

• Low to moderate loads: losses are primarily mechanical and magnetic (core losses).
• High-demand conditions: stator and rotor losses, mainly copper losses, become more dominant.

When benchmarking PMSMs against non-magnet motors (EESMs or IMs), most components exhibit lower power losses, except for iron stator losses, which are considerably higher in non-magnet motors. Additionally, due to greater copper content, copper losses in non-magnet motors can account for 50-60% of total motor losses⁸.

Enhancing both peak and continuous efficiency therefore requires a multi-faceted approach, which includes:

• advanced winding wire technologies to reduce resistance and improve cooling.
• improved thermal management to minimize energy losses by heat dissipation.
• innovative insulation materials to enhance performance.

Magnet wire is crucial for conducting electricity to generate the magnetic fields that power the rotor. Typically made from copper (or aluminum), the wire experiences electrical resistance, generating heat that must be managed. Direct cooling and advanced liquid cooling methods have the ability to moderate magnet wire operating temperatures, reducing heat dissipation and energy losses. Additionally, new insulation materials, including potting resins, slot liners, and magnet wire coatings, enhance thermal conductivity, electrical performance, and durability.

The type of magnet wire used directly influences efficiency by reducing power or ohmic losses and enabling new stator technologies. The magnet wire’s dimension and geometry play a big role in balancing loss forces like skin-effect or eddy-currents, especially in today’s high-frequency switching systems.

The transition from round to rectangular wire appears to favor conductive cross-sections of 5-10 mm² for common motor power requirements. Hairpin wire designs that use flat wires, such as Ampact™, have set the industry standard thanks to their ideal balance between performance, cost, and manufacturability. However, thinner wire sections like Litz wire offer additional potential for further copper loss reduction.

Magnet wire insulation plays a vital role in performance. Traditionally, enamel-based coatings with thermal resistance up to 200 °C were used in EVs. Modern 400V architectures rely on PAI and PI-coated wires
(70-100 µm thick), whereas 800V systems require insulation thicknesses of 150µm or higher. Polyetheretherketone or PEEK insulation is a superior alternative, offering:

• Higher thermal resistance (up to 240 °C), ensuring greater durability.
• Better insulation performance, with a lower relative permittivity of 3.2.
• Solvent-free processing, allowing for extrusion and injection molding instead of multi-layer dip and cure processes that rely on solvent-based formulations.

By leveraging PEEK coatings, e-motor designers can enhance motor efficiency and power output while enabling more compact and lightweight designs without sacrificing performance. Since EV driving range remains a key concern for consumers, improving efficiency through PEEK-coated magnet wires is a preferred strategy.

Several studies have demonstrated the impact of PEEK in e-motors, particularly as a material for slot-liners (replacing incumbent technologies such as NKN composites) and magnet wire coatings. Simulations replacing conventional materials with PEEK-based alternatives (without altering motor design) have resulted in improving motor efficiency by up to 2%, increasing torque output by 15%, and lowering winding temperatures by 20-40 °C. Additionally, it successfully reduced material consumption, total weight, and CO₂ emissions, thus contributing to sustainability goals.

PEEK coatings facilitate continuous winding (wave winding) designs, which allow for tighter bends, reduce extrusion defects, and support more compact stator designs. Moreover, continuous winding technologies require robust coatings, able to cope with the higher abrasion resistance such methods provoke; Wave-wound stator designs can shorten motor length by up to 10mm, decrease welding requirements by 90%, and boost efficiency by more than 1% compared to traditional hairpin solutions¹¹. A prime example of this is Ampact™, the PEEK-coated flat wire solution designed by Bekaert.

Beyond insulation, winding wire geometry and mechanical stability will continue to shape next-generation e-motor designs. By leveraging PEEK coatings, optimizing wire geometry, and refining production techniques, automakers can enhance efficiency, reliability, and sustainability in EV drivetrains.

In conclusion, the transition to 800V motor technology offers significant benefits, but is not without challenges. Beyond the substantial investments required by OEMs to adapt production platforms, many key components for an optimal 800V drivetrain remain costly and require further optimization. Additional challenges include electromagnetic interference (EMI) within the inverter and longer discharge times, which can lead to increased energy losses and delayed electrical discharge in crash scenarios¹². Thirdly, not all EV users may fully benefit from 800V advantages, particularly those who drive shorter distances or charge less frequently.

Main 800V System challenges

• Battery degradation (increased cell T° needs to be dealt with)
• More series connections (lower levels of redundancy)
• Powertrain re-design (vs. legacy designs): motor, inverter, cabling (busbar)
• Infrastructure upgrade for fast DC charging (200 à 400kW)

Despite all of these hurdles, OEMs and manufacturers worldwide are accelerating the adoption of high-voltage EVs, even in budget-friendly segments. As e-motor efficiency becomes increasingly central to EV performance, high-efficiency winding wire technologies and thermal-resistant insulation materials will be pivotal in shaping next-generation electric mobility.

Research highlights that innovations in PEEK-coated insulation, optimized wire geometries (flat wires and hairpin designs), and advanced production techniques (continuous winding) can significantly enhance motor efficiency and durability. The challenge ahead lies in scaling these innovations for mass adoption, ensuring cost-effectiveness, sustainability, and long-term performance in future BEVs.

Start today by exploring Ampact™, the magnet wire designed to power up high-voltage mobility.

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