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As new energy vehicles continue to iterate towards high voltage, ultra-high speed, high power density, and long durability and reliability, traditional round enameled wires are no longer able to meet the mass production demands of 800V high-voltage platforms, SiC high-frequency inverters, and 20,000rpm+ ultra-high-speed drive motors due to their low slot fill rate, poor heat dissipation, high-frequency loss, and lack of structural stability.
Flat Enameled Copper Wire (Flat Enameled Copper Wire) for automotive use has become the core standard wire for new generation of new energy main drive motors by virtue of its high slot fullness, low ohmic loss, excellent thermal conductivity, strong mechanical structure stability and high frequency insulation reliability.
Under the industrial trend of miniaturization, lightweight and high efficiency of new energy vehicle motors, the motor winding, as the core carrier of electromechanical energy conversion, directly determines the motor’s power density, efficiency range, temperature rise performance and full life cycle reliability. Traditional round enameled wire windings are affected by the circular cross-section stacking gap, the slot full rate is generally only 40%-45%, a large number of air gaps in the slot not only reduces the effective conductive cross-sectional area, but also impedes the conduction of heat, resulting in large copper losses in the windings, high temperature rise, and difficult to improve the power density, which can not be adapted to the current high-power, high-rpm, high-voltage inverter in the automotive harsh operating conditions.
Flat enameled copper wire adopts a regular rectangular cross-section design, which can realize a tight gapless layout, increase the motor slot fullness rate to 65%-70%, significantly increase the utilization rate of copper in the slot, and break through the motor power density bottleneck from the material side. At the same time, the larger heat dissipation contact area and more uniform current distribution of flat copper wire can effectively reduce the DC loss of the winding and high-frequency additional loss, widen the efficient operating range of the motor, reduce the energy consumption of the whole vehicle, and improve the range performance.
Unlike ordinary industrial flat copper wires, EV flat copper wires for automotive use need to withstand long-term high-frequency PWM pulse voltage, transient high-voltage shock, wide temperature range of hot and cold alternation, high-speed centrifugal vibration, oil-cooled media immersion, hot and humid salt spray corrosion and other multi-load coupling conditions, which puts forward very high automotive requirements for insulation system, paint adhesion, dimensional accuracy, bending resistance, corona aging resistance, refrigerant corrosion resistance and other indexes. Relying on the special formula system, precision molding equipment, automated coating production line and the whole chain reliability verification system, professional EV wire manufacturers have realized the standardization, customization and high consistency mass production of automotive flat copper wires, which has become the core basic guarantee for the upgrading of new energy motor industry chain.
In response to the differentiated needs of new energy vehicles for 400V conventional platform, 800V high-voltage platform, ultra-high-speed motors, oil-cooled/water-cooled heat dissipation, and long-durability vehicle standards, professional manufacturers have built a graded automotive flat copper wire product matrix, covering four core categories: conventional heat-resistant, ultra-high heat-resistant, corona-resistant, and high-voltage insulated, which is suitable for the full range of scenarios for passenger cars, commercial vehicles, hybrid models, and high-performance vehicles. Customized demand.
Flat enameled copper wire for automobiles consists of a high-purity oxygen-free copper conductor and a multi-layer composite insulating varnish film. The conductor is made of 99.95% or more high-purity oxygen-free copper, which has a high electrical conductivity, low electrical resistivity, and uniform grain size, which can minimize the copper loss and enhance the current-carrying capacity. Conductor after precision rolling, annealing softening treatment, both high strength and excellent flexibility, can be adapted to Hairpin hairpin winding precision bending, shaping, embedded line mass production process, no conductor deformation after bending, no stress residue.
Insulation layer adopts multi-layer gradient composite coating structure, abandoning the single-layer insulation of a single design flaws, through the bottom layer of adhesion layer, the middle layer of heat-resistant body layer, the surface of the wear-resistant layer of corrosion-resistant layered formula design, taking into account the processability, thermal stability, mechanical strength and chemical resistance, structurally solving the automotive flat copper wire processing easy to crack, easy to run, easy to age, easy to erosion of the media, such as the industry’s pain points.
Adopting PEIW polyester imide insulation system, heat-resistant grade 180℃, with good insulation stability, outstanding cost performance and high maturity in mass production, suitable for 400V platform, medium and low power, conventional working conditions of hybrid and pure electric passenger car stator winding, meet the durability standard of 8 years/150,000km for common household models, and it is the main supporting product for economical new energy motors.
The bottom layer is made of polyester imide to ensure the adhesion of paint film and bending technology, and the top layer is made of polyamide imide (PAI) ultra-high heat-resistant resin, the overall temperature-resistant grade exceeds 220℃, which has strong mechanical abrasion resistance, tensile strength, vibration resistance, and excellent resistance to cooling oil, hydrolysis, and corrosion resistance to heat and humidity. This series of products is designed for rotor confinement, high temperature accumulation, high-speed centrifugal vibration, oil-cooled immersion conditions, widely used with 800V high-voltage platforms, 200kW or more high-power main drive motors, is the mainstream configuration of the current high-end production models.
In PAI composite insulation system doped with nano-alumina, silica inorganic modified filler, reconfiguration of the insulation layer microscopic dense structure, can effectively inhibit high-frequency PWM pulse-induced partial discharge and corona bombardment, and significantly increase the PDIV partial discharge onset voltage. Ordinary flat copper wire high-frequency pulse life is only a few hundred hours, modified corona-resistant products can be run stably for more than 10,000 hours, perfectly adapted to SiC high-frequency frequency conversion motors, ultra-high-speed high-voltage main drive motors, to solve the problem of high-voltage platform motor insulation aging, intermittent short-circuit problems.
Adopting full polyimide insulation system, the long-term temperature resistance can reach 240℃-260℃, with extreme high and low temperature impact, radiation resistance, strong corrosion resistance, suitable for aerospace vehicle-mounted equipment, special high-temperature motors, extreme working condition test models, high-end performance car exclusive motors, and other special scenarios, to meet the demand for extreme reliability.
The technology iteration of automotive flat copper wire has fundamentally solved the many shortcomings of traditional round enameled wires for new energy motors, and has realized comprehensive upgrades in the five dimensions of space utilization, loss control, heat dissipation performance, mechanical stability, and insulation reliability, which has become the core support for mass production of high power density motors.
Traditional round wire windings have a large number of irregular air gaps due to round cross-section stacking, making it difficult for the slot fullness rate to exceed 45%, and a large amount of slot space is wasted, making it impossible to enhance the effective conductive cross-sectional area. Flat copper wire adopts rectangular regular structure, which can be tightly fitted and neatly arranged in the stator slot, with no unnecessary air gap, and the slot fullness rate reaches 65%-70% stably. Under the same conditions of core slot type and volume, flat copper winding can increase the effective copper cross-sectional area by 15%-20%, which greatly improves the current-carrying capacity and increases the power density of the motor by 5%-8%, and contributes to the miniaturization of the motor and the lightweight design, which effectively reduces the weight of the whole vehicle and optimizes the space layout.
Larger effective conductor cross-sectional area can directly reduce the DC resistance of the winding, significantly reducing the copper loss under low-speed steady state operating conditions. At the same time, the winding structure of flat copper wires makes the current distribution more uniform, which can effectively weaken the skin effect and neighborhood effect under high-frequency working conditions, and reduce the high-frequency additional loss. Under the full range of working conditions, the comprehensive loss of flat copper wire motors can be reduced by 8%-12%, and the coverage ratio of the motor’s high-efficiency zone (≥90% efficiency) is greatly increased, which directly optimizes the performance of the vehicle’s power consumption and improves the comprehensive range of new energy vehicles.
Air is a poor conductor of heat, and a large number of air gaps inside the round wire windings will seriously hinder heat conduction, leading to heat buildup in the windings, excessive local hot spot temperatures, and accelerated insulation aging. Flat copper wire close fit structure greatly reduces the air gap in the slot, the contact area between conductor and core, insulation paint significantly increased, heat can be quickly dissipated through the core and cooling medium conduction. At the same time, the flat outer surface of the flat wire is suitable for oil-cooled and water-cooled heat dissipation system, with higher heat exchange efficiency, which can effectively reduce the steady-state temperature rise of the winding and the transient peak temperature rise, avoid high-temperature thermal failure, and protect the motor’s ability to sustained output at high loads.
The automotive flat copper wire windings have a neat structure and strong integrity after molding, and with the VPI vacuum immersion paint curing process, they can form a rigid integrated winding structure. Compared with loosely stacked round wire windings, flat wire windings have greatly improved vibration and centrifugal resistance, and can withstand high-speed centrifugal force of more than 20,000 rpm and vehicle bumps for a long period of time, thus eliminating micro-vibration of the windings, varnish abrasion, turn-to-turn short-circuits and other failures, and greatly enhancing the reliability of the motor throughout the entire lifecycle of the durability of the motor.
Round wire windings have messy inter-turn and inter-layer gaps, and the electric field is unevenly distributed, making it very easy for the electric field to be concentrated locally, inducing corona discharges and insulation breakdowns. Flat copper wire flat fit arrangement makes the inter-turn gap uniform, the electric field distribution smooth, no local high-voltage concentration points, with corona-resistant insulation system, can significantly improve the winding partial discharge starting voltage, suitable for 800V high-voltage high-frequency inverter working conditions, effectively slow down the aging of the insulation, reduce the probability of motor failure.
The high-end performance of automotive flat copper wire relies on the specialized and precise automotive-grade manufacturing process. Ordinary industrial flat copper wire production process cannot meet the stringent requirements of automotive bending and crack resistance, high dimensional accuracy, no pinholes in the enamel film, and high consistency of insulation. Professional EV wire manufacturers have established a full closed-loop mass production system from conductor pre-treatment, precision rolling, multi-layer coating, high-temperature curing, precision slitting, performance testing, to finished product encapsulation, to ensure that the automotive-grade consistency of the quality of each batch of products.
High-purity oxygen-free copper rod is used as the raw material, and after many passes of precision cold rolling molding, the length and width dimensions of the flat wire, the arc of the rounded corners, and the thickness tolerance are accurately controlled, and the dimensional accuracy is controlled within ±0.01mm, to ensure that the windings are neatly laid out and tightly fitted. After molding, the gradient annealing process is adopted to eliminate the internal stress of the conductor and balance the hardness and flexibility of the wire to ensure that there is no cracking or deformation of the conductor during high-speed bending and hairpin molding, which is suitable for the automated Hairpin mass-production line.
Adopting multiple precision coating and segmented high-temperature curing process to replace the traditional single thick coating process. Through the bottom layer of adhesion special paint, the middle layer of heat-resistant body paint, the top layer of wear-resistant and corrosion-resistant paint layered precision coating, each layer of paint film uniform curing, no air bubbles, no pinholes, no uneven thickness defects. The multi-layer composite structure effectively solves the problems of brittle single-layer paint film, poor adhesion and easy to crack after bending, so that the paint film and the copper conductor are tightly bonded, and the paint film is intact without cracks after bending, which meets the requirements of precision winding molding process.
The production line is integrated with an online automatic inspection system, which monitors the wire size tolerance, varnish thickness, pressure resistance, number of pinholes and surface flatness in real time, and automatically rejects defective products. Offline sampling carries out a full set of automotive-grade reliability tests, such as high-temperature aging resistance, corona resistance, oil immersion resistance, cold and thermal shock, and bending and abrasion resistance, to ensure that the product’s electrical properties, mechanical properties, and chemical resistance meet the standards, and to eliminate batch quality anomalies.
Finished products are sealed and encapsulated with dust-free and moisture-proof sealing, accompanied by a constant temperature and humidity storage environment to prevent moisture, oxidation, and surface contamination of wires, and to ensure the optimal condition of the factory. At the same time, we have established a complete batch traceability system, which can trace the whole chain from raw materials, production parameters, testing data, and outgoing records to meet the requirements of IATF16949 automotive quality management system of automobile enterprises.
As a professional manufacturer of automotive solenoid wires, we strictly follow the IATF16949 quality management system in the automotive industry, and establish an exclusive EV reliability verification system that far exceeds the industrial standard, covering the four major dimensions of electrical, thermal, mechanical, and chemical, to comprehensively simulate the entire vehicle full-working conditions and the full-life cycle of the use of the environment, and to ensure that the products are stable and reliable in the long term.
In terms of electrical reliability, high-frequency pulse withstand voltage test, partial discharge PDIV test, industrial frequency withstand voltage test, and insulation resistance continuity test are carried out to ensure that the wires are suitable for 800V high-voltage and SiC high-frequency frequency conversion conditions, and that there will be no insulation breakdown or partial discharge aging failure for a long period of time. In terms of thermal reliability, the company conducts long-term thermal aging tests at 180℃, 200℃ and 220℃, as well as high- and low-temperature thermal shock tests (-40℃~180℃), to verify the thermal stability of the paint film and its ability to resist temperature change.
In terms of mechanical reliability, repeated bending, stretching, abrasion resistance, paint film adhesion test, simulation of winding into shape, high-speed vibration, long-term bumpy conditions, to ensure that the paint film is not peeling, cracking, no wear and tear. In terms of chemical reliability, special cooling oil immersion, wet aging and salt spray corrosion tests are carried out to verify the wire’s resistance to media erosion and hydrolysis, and to match the long-term immersion of oil-cooled motors in the working environment. All products can be supplied in bulk only after passing a full set of automobile regulation verification, which guarantees the quality of the motor and the durability of the whole vehicle from the source.
Relying on the gradient product system and mature mass production capability, flat copper wire for automotive applications can be fully adapted to various power motor scenarios of new energy vehicles, providing precise customized solutions for different working conditions and realizing the optimal matching of performance and cost.
In 400V platform economic passenger cars and hybrid models, 180℃ polyester imide flat copper wire program is adopted to meet the power output and durability requirements of regular working conditions, with outstanding cost performance, mature mass production, and suitable for mass popularization models.
In the 800V high-voltage platform, high-power high-performance pure electric models, PEI + PAI composite corona-resistant flat copper wires are equipped as standard, taking into account ultra-high heat resistance, high-voltage resistance, high-frequency corona resistance, vibration and wear-resistant performance, supporting the motor’s high power density, high-efficiency, and long durability, and adapted to the high-end vehicle quality standards.
In the scenario of ultra-high-speed motors and oil-cooled motors, the customized upgraded high oil resistance and high thermal conductivity modified flat copper wires strengthen the resistance of the paint film to hydrolysis and refrigerant corrosion, optimize the thermal conductivity structure, and solve the problem of insulation aging under the high-speed, high-temperature, medium-immersion coupling working conditions.
In the special vehicle and extreme working condition equipment, we provide PI polyimide ultra-high temperature resistant special flat copper wires to meet the demand for reliable operation under extreme high temperature, radiation and strong corrosive environments, covering niche high-end special vehicle scenarios.
Flat enameled copper wire is the core material for the upgrading and iteration of new energy vehicle drive motors, and it is also the key support for realizing high power density, high efficiency, high reliability and long durability of motors. Compared with traditional round wire products, automotive EV-grade flat copper wire has all-round advantages in space utilization, loss control, heat dissipation, mechanical stability, insulation reliability, and is perfectly suited for new energy vehicles with high voltage, high frequency, high speed, high temperature, strong vibration, and dielectric corrosion in the extreme composite working conditions.
Relying on the mature gradient product system, precision manufacturing process, strict automotive quality control system and rich experience in engineering support, the professional automotive wire manufacturer can provide new energy vehicle enterprises, motor manufacturers with standardized, customized, mass production of high-end flat copper wire solutions, and continue to help new energy automotive power system to reduce losses, improve efficiency, increase reliability, and promote the new energy automotive industry to a higher quality, high performance, longer durability direction. Higher performance, longer durability and sustainable development of the new energy automobile industry.
