Electric Vehicle Flat Wire Motors Used in  BYD, SAIC, and Tesla

What is a flat wire motor, and why is it gaining so much attention in the world of electric motor technology? Since their invention, motors have primarily used windings with a circular cross-section. However, these traditional round wire stator windings leave significant gaps when coiled, resulting in a coil fill factor of only 35% to 45%. In contrast, flat wire motors increase the bare copper slot fill rate by 20% to 30%, reducing motor volume and improving efficiency.

Evolution of Flat Wire Winding In EV Motors

Electric vehicle flat wire motors, as opposed to round wire motors, are a novel type of motor that emerged relatively recently. The distinction lies in the shape of the stator winding wire. Traditional motor stator windings use round wire, while flat wire motors use a flat, rectangular wire. The flat wire motor was first introduced in the Chevrolet VOLT plug-in hybrid vehicle in 2007. Due to the shape of its stator winding wire, it is also known as a hairpin flat wire motor.

BYD’s 6 Layer Flat Wire Motor

BYD’s mass-produced eight-in-one electric powertrain is the world’s first, aimed at reducing the weight of electric vehicles. Reducing weight means lowering energy consumption, and decreasing volume can increase passenger space or battery capacity.

This eight-in-one electric powertrain achieves a comprehensive efficiency of over 89%, integrating the drive motor, reducer, DC converter, vehicle controller, motor controller, on-board charger, power distribution box, and battery manager.

The drive motor utilizes a six-layer flat wire oil-cooled motor technology, reducing the overall size and achieving higher drive efficiency. Due to the integration of this powertrain, the comprehensive drive efficiency of this six-layer flat wire motor can rival that of an eight-layer flat wire motor in the industry.

BYD flat wire motor

SAIC’s 8 Layer Flat Wire Motor

SAIC’s Feifan Auto brand, fully funded by SAIC Group, benefits from the technical advantages and resources of a large enterprise, pioneering direct waterfall oil cooling technology. In the Feifan F7, the stator’s midsection is divided into grid-like oil cooling channels, allowing lubrication oil to penetrate every corner of the motor. This significantly enhances the heat exchange efficiency of the stator windings, improving cooling capacity by 30% to 70%.

Compared to traditional technology, the peak power duration of the entire motor in the Feifan F7 is extended by 2-3 times. Additionally, the constant to peak power ratio increases by 40%, with a rated power of 160kW, far surpassing other models in its class. The eight-layer hairpin flat wire winding layout of the Feifan F7 achieves a higher packing density, reducing heat loss by 20%-30%. This ensures battery safety and high burst efficiency after cooling.

Aside from SAIC’s Feifan and IM electric vehicle flat wire motor market size, other domestic brands like Geely’s Zeekr and Dongfeng’s Voyah, along with third-party manufacturers like Fangzheng Motor, Tianjin Songzheng, and Huayu Electric, are continuously research and development eight-layer flat wire motors.

SAIC flat wire motor

Tesla’s 10 Layer Flat Wire Motor

Tesla’s third-generation 3D6 flat wire motor continues to use a 6-pole, 54-slot configuration. The motor utilizes the popular HairPin flat wire winding and features a large welded end copper bar for output. This design allows the motor to achieve a maximum power of 202kW and a peak torque of 404Nm.

Each slot in the 3D6 motor’s flat wire has five weld points, meaning there are ten wires per slot. From the end view, two external star-shaped copper bars gather three branches for each of the A, B, and C phases. The parallel configuration of the motor uses six parallel paths, indicating a high-current, low-voltage design.

A unique aspect of the 3D6 motor is the elimination of the coating process on the winding ends. The welding heads and copper bars are exposed. While most domestic brands use coating to meet electrical clearance requirements, Tesla opted for this unconventional approach to reduce costs. Although coating is crucial for electrical safety, the need to cut costs overrode the technical requirements, leading Tesla to this bold decision.

Tesla’s fourth-generation flat wire motor returns to an eight-layer winding configuration. The third-generation motor faced greater manufacturing challenges, lower yield rates, and no significant performance advantages over the widely adopted eight-layer flat wire motors in the industry. This prompted the shift back to the more conventional eight-layer design.

A standout feature of Tesla’s flat wire motor is the carbon fiber protective sleeve added to the rotor. This sleeve’s primary role is to enhance the rotor’s structural strength and prevent permanent magnet detachment at high speeds. Commonly used neodymium-iron-boron materials can withstand significant compressive stress but not tensile stress, with tensile strength being only a tenth of compressive strength. The carbon fiber sleeve addresses this by providing high tensile strength, excellent insulation, and high-temperature resistance.

Tesla flat wire motor

Advantages in 8 Layer Flat Wire Motor in New Energy Vehicles

Eight-layer flat wire motors are considered optimal in the industry. Comparing four-layer and eight-layer hairpin winding motors, the efficiency of eight-layer windings at over 90% is 88.8%, while four-layer windings are at 83.9%, making eight-layer windings about 5% more efficient.

Additionally, the average energy consumption of eight-layer flat wire motors decreases from 13.8kWh/100km to 12.2kWh/100km, a reduction of over 11.5%.

The efficiency and high-efficiency area ratio of eight-layer flat wire motors are higher than those of four-layer motors, demonstrating that increasing the number of flat wire winding conductor layers significantly reduces AC losses. Increasing conductor layers can also effectively enhance system voltage and power, aligning with the current 800V high-voltage trend.


The global electric vehicle flat wire motor market is experiencing significant growth due to the increasing demand for electric vehicles and the focus on reducing carbon emissions. Flat wire motors represent a significant advancement in electric motor technology, offering enhanced efficiency, reduced size, and better heat management compared to traditional round wire motors. 

With continuous development and integration in electric vehicles by major manufacturers like BYD, SAIC, and Tesla, flat wire motors are poised to become a standard in the industry, and increase market share.


How Does A Flat Wire Motor Differ From A Traditional Round Wire Motor?

A flat wire motor differs from a traditional round wire motor primarily in the shape of its winding wires. Flat wire motors use rectangular wires, allowing for a higher fill factor in the stator slots. This design reduces resistance, improves thermal management, and enhances overall efficiency.

The compact arrangement of flat wires also reduces the motor’s size and weight while increasing power density, making them more efficient and effective in applications like electric vehicles and industrial machinery compared to round wire motors.

What Types Of Flat Wire Motors Are There?

Hair-Pin Flat Wire Motors: These motors use hairpin-shaped wires for winding, offering high packing density, improved thermal management, and enhanced efficiency.

X-Pin Flat Wire Motors: Featuring an X-shaped winding pattern, these motors are designed to optimize space utilization and reduce electrical losses, enhancing overall motor performance.

I-Pin Flat Wire Motors: Utilizing straight, I-shaped winding configurations, these motors focus on simplicity and efficiency, providing robust performance for various applications.

S-Winding Flat Wire Motors: These motors use an S-shaped winding pattern, which helps in balancing the magnetic fields and reducing noise and vibrations, resulting in smoother and quieter operation.

Try to contact us for high-quality motor cores in China.