Hairpin motors optimize electric vehicle (EV) performance and range with flat, rectangular copper windings. Many high-performance EVs use permanent magnet synchronous motors (PMSMs) with hairpin windings to minimize energy losses and maximize power output. Like their conventional round-wire motor counterparts, hairpin configurations generate electromagnetic force through copper windings wrapped around iron cores.
As electric current flows through these windings, it creates a magnetic field that interacts with the rotor’s permanent magnets, inducing and maintaining rotation.
This article discusses how hairpin motors increase stator winding efficiency and maximize EV performance with higher power density, improved thermal management, and enhanced structural integrity. It also highlights the Porsche Taycan as a real-world example of hairpin motors in action, reviews the challenges of hairpin motor manufacturing, and explores scaling the technology for broader adoption beyond high-performance EVs.
How hairpin motors optimize stator winding efficiency
EV motors consist of two primary components: the rotor, which rotates at the center, and the stator, which remains stationary on the outer side. In conventional round-wire PMSMs used in EVs, the stator contains long iron cores wrapped with bundles of stranded copper wire running parallel to the longitudinal axis. These bundles require stator lacing, a labor-intensive process where individual strands are stitched together to maintain structural integrity.
As shown in Figure 1, hairpin motors replace stranded wire with solid, rectangular copper conductors bent into a distinctive hairpin shape. These conductors are inserted into stator slots, then twisted and welded at their ends, eliminating the need for lacing. Their rectangular cross-section increases the copper fill factor, reducing electrical resistance and improving conductivity.
Figure 1. A comparison of round-wire and hairpin motor windings, showing distinct geometry and implementation. (Image: Honest)
Maximizing EV performance with higher power density
As shown in Figure 2, hairpin motors increase power density by improving copper-stator slot utilization. This reduces electrical resistance and enables higher power output — up to 4.5 kW/kg in some designs, compared to approximately 3.5 kW/kg for traditional round-wire motors.
Figure 2. A comparison of conventional round-wire and hairpin motor windings, highlighting the higher slot fill rate. (Image: Lucid Motors)
Higher power density increases torque output from a smaller motor, reducing weight while improving acceleration and responsiveness. Moreover, the electromagnetic properties of hairpin windings improve current distribution, minimizing electrical losses and optimizing performance.
Hairpin motors also improve thermal management by increasing surface area for heat dissipation, lowering temperature rise by 5 to 10% and extending motor lifespan. By reducing direct current (dc) losses, they improve efficiency by up to 20% in some EVs compared to round-wire windings. Lastly, their precision-welded conductors in PMSMs minimize vibration and electromagnetic noise during operation.
Hairpin motors in action: driving the Porsche Taycan
As shown in Figure 3, the Porsche Taycan EV features dual hairpin motors, achieving a nearly 70% copper fill factor to maximize power density.
Figure 3. The Porsche Taycan, powered by dual hairpin motors. (Image: Porsche)
Featuring a hairpin winding design, the Taycan’s high-efficiency PMSMs convert over 90% of electrical energy into propulsion. In the high-performance Turbo S model, these motors deliver up to 560 kW (751 hp).
Other automotive manufacturers have also adopted hairpin windings to boost motor performance. Hyundai and Kia, for example, integrate this technology into their Electric Global Modular Platform (E-GMP), achieving approximately 10% greater efficiency than conventional motors. Models like the Hyundai Ioniq 5 and Kia EV6 benefit from these gains, bolstering power delivery and extending range.
Challenges in hairpin motor manufacturing
Although hairpin motors offer significant efficiency and performance advantages, their complex manufacturing process presents challenges that limit wider adoption. Unlike conventional round-wire motors, hairpin stator production demands specialized expertise, extensive training, and advanced automation.
In Figure 4, you’ll note that each hairpin must be carefully twisted and inspected before assembly due to tight positional tolerances.
Figure 4. The precision inspection of a hairpin conductor before stator assembly, ensuring precise alignment and insulation integrity. (Image: Control)
Additional challenges in large-scale hairpin motor manufacturing include:
- High precision: Unlike round-wire windings, which can be insulated after forming, hairpin conductors must be bent without damaging the insulation, increasing quality control demands. Additionally, thick copper wires require precise pre-compensation to ensure accurate insertion and prevent misalignment resulting from elasticity or rebound.
- Limited design flexibility: Hairpin motors have fewer turns per slot than round-wire motors. As a result, even small design changes — such as adjusting the number of conductors — can significantly impact performance.
- Ac copper losses: In thicker rectangular copper wires, the skin effect concentrates current on the conductor’s surface, increasing resistance and reducing efficiency at high frequencies. The severity and impact of these losses depends on electromagnetic design parameters, including magnetic flux density, slot height, and wire dimensions.
Scaling hairpin technology for broader EV adoption
Despite these challenges, advancements in automation, material processing, and cost-sharing strategies are expected to streamline hairpin motor production scalability and drive broader adoption in high-performance EVs. Future innovations may combine hairpin and round-wire advantages or introduce new winding technologies that improve performance while simplifying design and cost.
In the meantime, conventional round-wire windings are a cost-effective, scalable option for entry-level and mid-performance EVs prioritizing simplicity and affordability. Hairpin windings will likely remain the preferred choice for premium EV traction motors, excelling in high-performance scenarios demanding power density, efficiency, and heat dissipation.
Conclusion
Hairpin windings in PMSM motors improve EV performance and range by increasing power density, optimizing thermal management, and enhancing structural integrity. Although their manufacturing process is more complex than conventional round-wire PMSM motors, several EVs — including the Porsche Taycan, Hyundai Ioniq 5, and Kia EV6 — effectively implement this technology. Scalable production innovations will likely expand hairpin motor adoption in high-performance EVs and drive broader use across more vehicle categories.
References
- The Fascinating World of Hairpin Motors: Revolutionizing EV Efficiency, Reports Globe
- What is a Hairpin Motor – Benefits & Assembly Process, LaserAx
- Is the Hair-Pin Motor the Vanguard of EV Drive Technology?, BrogenMotors
- Understanding Hairpin Stators in High-Efficiency Motors, Control
- The Ultimate Showdown: Round Wire vs. Hair Pin Motor Winding, Mohit Mistry
- Porsche Taycan Drivetrain, Porsche
- Hairpin Technology, BBS Automation
- Hairpin Technology, Accurex
- What is a Hairpin Motor?, Honest
- The Advantages of Hairpin Motor Compared to Traditional Motor, Honest
- The Development Status of Automobile Hairpin Winding Technology, Honest
Related EE World content
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Filed Under: Electric Motor, FAQs