240°C Special High Temperature Resistant Enameled Copper Wire

I. Introduction: 240 °C enameled wire – “heat-resistant backbone” of ultra-high-temperature electrical equipment

Among the performance requirements of modern motors, transformers, and electrical equipment, * * high temperature resistance * * has become one of the most critical reliability indicators. When the operating temperature rises from 130 °C to 180 °C, 200 °C, and then climbs to 240 °C, the organic paint film of traditional enameled wires will exhibit failure modes such as thermal aging, breakdown, and peeling within hours to tens of hours, resulting in equipment downtime and even safety accidents.

* * 240°C special high-temperature resistant enameled copper wire * * is the high-performance winding material developed to address this extreme condition. The paint film system adopts polyamide-imide (Pai) + polyimide (PI) composite structure, or pure PI, or peek and other special engineering plastic paint films, which can maintain excellent electrical insulation, mechanical strength and chemical stability at 240 °C continuous working temperature. With more than ten years of special enameled wire R&D and manufacturing experience, LP Winding Wire can provide customers around the world with Φ 0.10-3.00 mm full specifications of 240 °C high temperature resistant enameled copper wire products.

This article will systematically introduce the core technology, performance advantages, application areas, production processes, selection methods, test standards, and comparative analysis with conventional enameled copper wires at 240 °C to help engineers and procurement personnel establish a complete product awareness.

1.1 Position of 240 °C enameled wire in the enameled wire temperature classification system

The Thermal Class, developed by the International Electrotechnical Commission (IEC) and the National Electrical Manufacturers Association (NEMA), is a core metric for measuring the long-term heat resistance of enameled wires. The IEC 60172 standard divides enameled wires into multiple grades according to the Temperature Index (TI):

• B Class (130°C): Polyurethane (PU), Polyester (PE) and other common paint films
• F Class (155°C): Polyesterimide (PEI) paint film
• H Class (180°C): Polyamide-imide (PAI) paint film
• N Class (200°C): Polyamide-imide (PAI) modified paint film
• R Class (220°C): Polyimide (PI) paint film
• 240°C Class: Polyimide (PI) + Polyamide-imide (PAI) composite paint film, or specialty fluoropolymer, PEEK paint film

* * 240 °C enameled wire * * belongs to the “ultra-high temperature” grade in the enameled wire temperature grade system, second only to special grades such as 250 °C and 260 °C, which is much higher than ordinary B/F/H grade enameled wire. It has reached the industry-leading level in terms of thermal stability, chemical stability, mechanical strength, etc.

1.2 5 Core Benefits of 240°C Enameled Wire

Compared with conventional B/F/H grade enameled wire, * * 240 °C special high temperature resistant enameled copper wire * * has the following 5 core advantages:

* * Advantage 1: Ultra-high temperature long-term stability * *. At a continuous operating temperature of 240°C, the thermal aging life of the paint film exceeds 20,000 hours (tested according to IEC 60172 standard), far exceeding 20,000 hours for class H (180°C) enameled wires and 20,000 hours for class F (155°C) enameled wires. This means that 240 °C enameled wire can maintain long-term reliable operation under extreme working conditions of 240 °C.

* * Advantage 2: Excellent electrical insulation performance * *. The dielectric strength of PI paint film reaches 200-250 kV/mm, which is 3-4 times that of ordinary PU paint film (50-80 kV/mm). When the thickness of the paint film is 25-40 μm, the breakdown voltage can reach 8-15 kV, which can withstand higher operating voltage and surge impact.

* * Benefit 3: Excellent chemical stability * *. PI paint film has strong resistance to acid, alkali, solvent, oil, refrigerant and other chemical media, and can maintain the integrity of the paint film in extreme environments such as chemical corrosion, high-temperature oil immersion, and radiation. This feature makes it suitable for high demanding fields such as chemical industry, nuclear power, aerospace and so on.

* * Advantage 4: Wide temperature range adaptability * *. 240 °C enameled wire can not only work at 240 °C high temperature, but also maintain flexibility at -269 °C very low temperature, and the temperature adaptability range far exceeds that of conventional enameled wire. This makes it equally suitable for low-temperature environments such as liquid nitrogen, liquid helium, and polar regions.

* * Advantage 5: High mechanical strength and wear resistance * *. The wear resistance, scratch resistance, and cutting resistance of PI paint films are significantly better than those of conventional paint films. In the process of winding, embedding, shaping and other processes, the paint film is not easy to break, which can effectively avoid insulation failure caused by mechanical damage.

1.3 6 main application areas for 240°C enameled wires

240 °C special high temperature resistant enameled copper wire is mainly used in the following 6 fields:

* * Application 1: Traction motor * *. The operating temperature of traction motors such as electric vehicles, high-speed trains, and subways can reach 180-220 °C, and the local hotspot temperature even exceeds 240 °C. 240 °C enameled wires are ideal for traction motor windings, which can significantly improve the power density and reliability of the motor.

* * Application 2: Aeronautical motors and generators * *. Aero engines, auxiliary power units (APUs), and starter generators typically have winding operating temperatures between 200-260°C and require extremely light weight and high reliability. 240°C enameled wires can meet the stringent requirements of the aerospace industry.

* * Application 3: Aerospace propulsion systems * *. Rocket engines, solenoid valves for satellite propulsion systems, and sensor windings need to work in extreme high temperature, high radiation, and vacuum environments. The high heat resistance and low air release performance of 240 °C enameled wires (especially PI paint film) are essential characteristics for aerospace applications.

* * Application 4: Nuclear main pumps and steam generators * *. The windings of the main pump motor and the steam generator level gauge sensor of the nuclear power plant need to operate reliably in 200-300 °C steam environment and radiation environment for a long time. The paint film must be resistant to high temperature, radiation and hydrolysis. 240 °C PI enameled wire is the key material for nuclear power windings.

* * Application 5: Industrial high-temperature furnaces and heat treatment equipment * *. Sensor, inductor, and heater windings in industrial high-temperature furnaces such as metallurgy, glass, and heat treatment operate at temperatures up to 250-400°C. 240°C enameled wires can be applied to in-furnace windings below 250°C, and inorganic insulation (e.g. alumina, ceramics) schemes need to be considered for higher temperatures.

* * Application 6: Oil drilling and downhole equipment * *. The motor and sensor windings of petroleum deep wells and ultra-deep well drilling equipment can work at temperatures of 200-260 °C, and are in a high-pressure, corrosive drilling fluid environment. The high temperature resistance, oil resistance, and chemical resistance of 240 °C enameled wires fully meet the requirements of underground working conditions.

II. Chemical structure and performance basis of 240 °C paint film material

The core of the 240°C enameled wire is paint film material. This section will deeply analyze the chemical structure, heat resistance mechanism and performance characteristics of special paint films such as PI and Pai.

2.1 Chemical structure of polyimide (PI) paint film

Polyimide (PI) is a high-performance polymer produced by polycondensation of aromatic dianhydrides and aromatic diamines, whose molecular backbone contains the characteristic imide ring (-CO-N-CO-) structure:

• Chemical Structure: The main chain of aromatic PI is alternately connected by benzene rings, imide rings, ether bonds and other groups
• Molecular Weight: Typical PI weight-average molecular weight (Mw) is between 50,000-150,000
• Glass Transition Temperature (Tg): 250-300°C, much higher than 240°C working temperature
• Thermal Decomposition Temperature (Td): 500-600°C (5% weight loss temperature)
• Long-term Service Temperature: -269°C to +260°C (air atmosphere)

* * The heat resistance mechanism of PI coating film * * is that a large number of aromatic rings and imide ring structures in its molecular backbone form a rigid conjugate system, which has strong intermolecular chain force and high thermal motion resistance. Therefore, at a high temperature of 240 °C, the PI paint film does not undergo significant chain motion or decomposition reactions, and stable physical and chemical properties can be maintained.

2.2 Chemical structure of polyamide-imide (Pai) paint film

Polyamide-imide (Pai) is a high-performance polymer that combines the advantages of polyimide and polyamide, and its molecular backbone contains both an imide ring and an amide bond:

• Chemical Structure: PAI main chain is composed of imide rings, amide bonds, and aromatic rings
• Glass Transition Temperature (Tg): 270-290°C
• Thermal Decomposition Temperature (Td): 450-500°C
• Long-term Service Temperature: -200°C to +240°C (air atmosphere)
• Mechanical Strength: Tensile strength 150-200 MPa, elongation at break 10-20%

* * The advantage of Pai paint film * * is that it combines the heat resistance of PI with the toughness of PA. Compared with pure PI paint film, Pai paint film has better flexibility and better winding performance, but the heat resistance limit is slightly lower (240 °C vs 260 °C). Therefore, Pai is often used as a single layer of paint film for H-grade (180 °C) enameled wires, or as an outer layer of paint film with PI inner layer of paint film to form a Pai + PI composite paint film system for 240 °C enameled wires.

2.3 Composite structure of 240 °C paint film

240°C enameled wires are usually made of a double or triple composite structure to balance heat resistance, mechanical strength, and winding properties:

* * Double-layer structure * * (Pai + PI):

• Inner Layer (Base Coat): PI paint film, thickness 15-25 μm, provides main insulation and heat resistance
• Outer Layer (Top Coat): PAI paint film, thickness 10-15 μm, provides mechanical strength and wear resistance
• Total Thickness: 25-40 μm

* * Three-tier structure * * (PEI + Pai + PI or Pai + Pai + PI):

• Base Coat: PI or PEI paint film, thickness 10-15 μm
• Middle Coat: PAI paint film, thickness 10-15 μm
• Top Coat: PAI or PI paint film, thickness 10-15 μm
• Total Thickness: 30-45 μm

* * Advantages of composite paint film * *:

• Inner layer PI provides ultra-high temperature heat resistance and dielectric strength
• Outer layer PAI provides mechanical strength, wear resistance and winding performance
• Multi-layer structure can form gradient insulation performance, avoiding breakdown caused by single-layer defects

2.4 6 Key Performance Parameters of Paint Films

Key performance parameters for evaluating the quality of 240 °C enameled wire coating include:

* * Parameter 1: Paint film thickness * *. The total film thickness is usually 25-40 μm, too thin leads to insufficient insulation strength, too thick leads to a decrease in conductor filling rate and an increase in winding size. The film thickness of LP Winding Wire 240 °C enameled wire is divided into three grades: Grade 1 (25-32 μm), Grade 2 (30-38 μm), and Grade 3 (35-42 μm).

* * Parameter 2: Paint film continuity * *. The number of pinholes per 100 meters of paint film should be less than 1 (IEC 60851 standard) to ensure the integrity of the paint film. LP Winding Wire’s 240 °C enameled wire usually has 0-0.5 pinholes on a 100m length, far exceeding the standard requirements.

* * Parameter 3: Dielectric Breakdown Voltage * *. The breakdown voltage of the paint film at AC voltage shall meet the requirements of the IEC 60851 standard. The breakdown voltage of the 240 °C enameled wire PI paint film is generally between 8-15 kV (the thickness of the paint film is 30-40 μm), which is much higher than the 4-8 kV of the conventional B/F grade enameled wire.

* * Parameter 4: Heat Shock Resistance * *. Cracking performance of the paint film under impact at 200-260°C. The 240°C enameled wire shall be able to withstand thermal shock at 240°C for 30 min without cracking (tested according to IEC 60851-6 standard).

* * Parameter Five: Flexibility and Adhesion * *. The adhesion performance of the paint film when the wire is bent and stretched. The paint film of the 240 °C enameled wire should be able to withstand 1 × d (enameled wire diameter) of the round rod without cracking and peeling.

* * Parameter 6: Chemical Resistance * *. Paint film resistance to acid, alkali, solvent, oil and other chemical media. 240 °C enameled wire should be able to withstand 20% sulfuric acid, 20% sodium hydroxide, acetone, toluene, engine oil, transformer oil and other common chemical media after 24 hours of immersion paint film no significant change.

III. Production process of 240°C enameled wire

The production process of 240 °C special high-temperature resistant enameled wire is more complex than that of conventional enameled wire, requiring a higher level of process control.

3.1 Conductor materials and pretreatment

240 °C enameled wire usually uses high-purity oxygen-free copper (OFC) as the conductor material, copper purity ≥ 99.97%, oxygen content ≤ 10 ppm. The low oxygen content can avoid the oxidation of copper during high-temperature annealing and sintering of the paint film, ensuring the adhesion and electrical conductivity of the paint film.

Conductor pretreatment includes:

• Annealing Softening: Anneal hard copper wire at 400-500°C to obtain soft copper wire with elongation of 30-40%
• Surface Cleaning: Use acid cleaning, electrolytic cleaning, ultrasonic cleaning and other methods to remove oxide layer, oil stains, and lubricant residues on the copper wire surface
• Surface Roughening: Light mechanical or chemical treatment increases surface roughness of copper wire to improve paint film adhesion

3.2 Lacquer preparation and coating process

PI paints are usually coated with polyamide acid (PAA) precursor solution followed by a high-temperature imidation process:

* * Preparation of polyamic acid solution * *:

• Aromatic dianhydrides (such as pyromellitic dianhydride PMDA) and aromatic diamines (such as 4,4′-diaminodiphenyl ether ODA) in polar solvents (such as N-methylpyrrolidone NMP, dimethylacetamide DMAc)polycondensation reaction
• Reaction temperature 0-25°C, reaction time 6-24 hours
• The resulting PAA solution has solid content 15-25% and viscosity 1,000-5,000 cP

* * Coating process * *:

• Use die coating or felt coating method to uniformly apply PAA solution on the copper wire surface
• Coating speed 5-30 m/min (depending on paint film thickness and baking capacity)
• Coating thickness is precisely controlled by parameters such as die aperture, paint viscosity, and line speed

3.3 Baking and imination processes

The coated PAA film needs to be iminated in a high-temperature oven and converted into a PI film:

* * Baking oven structure * *:

• Multi-stage (6-12 stage) forced hot air circulation oven
• Each stage temperature is independently controlled
• Total baking length 12-30 meters
• Maximum oven temperature 450-550°C

* * Temperature gradient settings * *:

• Preheating section (80-150°C): remove solvent
• Imidization section (200-350°C): PAA converted to PI, release water
• Sintering section (400-500°C): PI paint film fully cured
• Cooling section (300-100°C): paint film cooled and shaped

* * Key process controls * *:

• Temperature control accuracy ±5°C
• Tension control accuracy ±5 g (avoid paint film stretching or shrinking)
• Baking atmosphere: fresh air supplement to ensure timely discharge of solvent vapor
• Exhaust system: handle volatile solvents (such as NMP), meet environmental requirements

3.4 Coating process of Pai paint film

Pai paint films are usually baked and cured after direct application of the Pai resin solution:

* * Preparation of Pai paint liquor * *:

• PAI resin dissolved in NMP or DMAc solvent
• Solid content 20-30%
• Viscosity 2,000-8,000 cP
• Add small amounts of leveling agents, thickeners and other additives

* * Coating and baking * *:

• Similar to PI coating process, but baking temperature is slightly lower (350-450°C)
• Baking time 30-60 seconds
• Paint film thickness controlled by die and coating speed

3.5 Coating process of double-layer paint film

For Pai + PI composite paint film structure, PI coating and Pai coating are required in order:

* * Typical process flow * *:

• Copper wire annealing, cleaning
• PI Base coat coating (Die 1) + baking
• Paint film thickness online measurement
• PAI Top coat coating (Die 2) + baking
• Paint film thickness online measurement
• Film continuity online detection (pinhole detection)
• Dielectric breakdown voltage online detection
• Take-up

CCPs

• Paint film temperature and humidity control between two coatings
• Paint film interface bonding force control (avoid delamination)
• Total paint film thickness accuracy ±2 μm

3.6 Special challenges for 240°C enameled wire production

The production of 240°C enameled wires faces the following special challenges compared to conventional enameled wires:

* * Challenge 1: High energy consumption of high temperature baking * *. The baking temperature is 100-150 °C higher than the conventional enameled wire, and the energy consumption is increased by 30-50%, which requires the optimization of the oven design and heat recovery system.

* * Challenge 2: Solvent Emission Control * *. Polar solvents such as NMP and DMAc have a large amount of volatilization and require a closed collection and treatment system, which meets VOC emission standards.

* * Challenge 3: Paint film quality control * *. Parameters such as the degree of PI imination, the crystallinity of the paint film, and the stress of the paint film need to be precisely controlled. Otherwise, problems such as cracking and delamination of the paint film are prone to occur.

* * Challenge 4: Production speed limits * *. The PI film needs to be fully imidized, the baking time is long, and the production speed is 30-50% lower than that of conventional enameled wire.

* * Challenge 5: Invest heavily in equipment * *. The investment in equipment for high-temperature ovens, solvent recovery systems, and imination control systems is 2-3 times that of conventional enameled wires.

IV. Key performance parameters and test methods of 240 °C enameled wire

240 °C enameled wire needs to pass a series of rigorous performance tests to meet the requirements of relevant international standards (IEC 60851, NEMA MW 1000, GB/T 6109) and specific industry standards (aviation, nuclear power, rail transit).

4.1 Electrical performance parameters

* * Dielectric Breakdown Voltage * *:

• Test Standard: IEC 60851-5
• Test Method: Immerse the enameled wire sample in metal beads, apply 50 Hz AC voltage, gradually increase the voltage until the paint film breaks down
• 240°C enameled wire requirement: Breakdown voltage ≥8 kV (paint film thickness 30-40 μm), actual usually ≥10-15 kV

* * Film Continuity * *:

• Test Standard: IEC 60851-5
• Test Method: Pass the enameled wire through a test tank containing mercury or electrolyte, short circuit is formed at the paint film pinhole, detect and count the pinholes
• 240°C enameled wire requirement: Number of pinholes per 30 m of paint film ≤3 (IEC Class 1), actual usually 0-0.5 per 100 m

* * Insulation Resistance * *:

• Test Standard: IEC 60851-5
• Test Method: Measure the insulation resistance of the enameled wire at 500V DC voltage
• 240°C enameled wire requirement: Insulation resistance ≥2,000 MΩ·m (20°C), ≥20 MΩ·m (240°C)

* * Dissipation Factor * *:

• Test Standard: IEC 60851-5
• Test Method: Measure the dielectric loss of the paint film under power frequency or high frequency voltage
• 240°C enameled wire requirement: tan δ≤0.01 (1 kHz, 20°C), ≤0.05 (1 kHz, 240°C)

4.2 Mechanical performance parameters

* * Elongation * *:

• Test Standard: IEC 60851-3
• Test Method: Stretch the enameled wire until fracture, measure the elongation at fracture
• 240°C enameled wire requirement: Elongation ≥25% (soft state), ≥10% (hard state)

* * Tensile Strength * *:

• Test Standard: IEC 60851-3
• Test Method: Stretch the enameled wire until fracture, measure the maximum tensile stress
• 240°C enameled wire requirement: 200-250 MPa (soft state), 350-450 MPa (hard state)

* * Flexibility and Adhesion * *:

• Test Standard: IEC 60851-3
• Test Method: Mandrel winding test, tensile test, scraping test
• 240°C enameled wire requirement: 1×d mandrel winding without cracking, paint film adhesion strong

* * Abrasion Resistance * *:

• Test Standard: NEMA MW 1000
• Test Method: Reciprocating scraping test, measure the number of scrapes required for paint film damage
• 240°C enameled wire requirement: Single scrape force ≥10 N

4.3 Thermal performance parameters

* * Heat Shock * *:

• Test Standard: IEC 60851-6
• Test Method: After heat shock of enameled wire at 240°C for 30 min, immediately perform 1×d mandrel winding
• 240°C enameled wire requirement: No cracking, no peeling

* * Thermal Aging * *:

• Test Standard: IEC 60172
• Test Method: Accelerate aging at three temperature points 240°C, 260°C, 280°C, measure the time for breakdown voltage to drop to the specified value
• 240°C enameled wire requirement: Temperature index (TI) ≥240, 20,000 hours life

* * Cut-Through Temperature * *:

• Test Standard: IEC 60851-6
• Test Method: Apply specified load on the enameled wire sample, gradually increase temperature until paint film softens and breaks down
• 240°C enameled wire requirement: Softening breakdown temperature ≥350°C

* * Thermal Weight Loss * *:

• Test Standard: ASTM E1131
• Test Method: TGA thermogravimetric analysis
• 240°C enameled wire requirement: 5% weight loss temperature ≥450°C

4.4 Chemical performance parameters

* * Solvent Resistance * *:

• Test Standard: IEC 60851-4
• Test Method: After immersing the enameled wire in standard solvents (such as xylene, acetone), measure the paint film hardness and adhesion
• 240°C enameled wire requirement: No obvious softening, blistering, peeling of paint film after immersion

* * Oil Resistance * *:

• Test Method: After immersing the enameled wire in transformer oil at 100°C for 24 hours, test the dielectric strength
• 240°C enameled wire requirement: Dielectric strength retention rate ≥80%

* * Hydrolysis Resistance * *:

• Test Method: After exposing the enameled wire at 95°C, 95% humidity for 1000 hours, test the dielectric strength
• 240°C enameled wire requirement: Dielectric strength retention rate ≥70%

* * Radiation Resistance * *:

• Test Method: After exposing the enameled wire to Co-60 γ-ray at 10⁶ Gy dose, test the dielectric strength
• 240°C enameled wire requirement: Dielectric strength retention rate ≥70%（PI paint film is especially suitable for nuclear power radiation environment)

V. Comparison of 240 °C enameled wires and conventional enameled wires

To help engineers and purchasing staff better understand the performance advantages of 240°C enameled wires, this section systematically compares 240°C enameled wires with regular B/F/H grade enameled wires.

5.1 Comparison of temperature levels

The enameled wires at 240°C have a much higher temperature rating (240°C) than conventional enameled wires at B (130°C), F (155°C) and H (180°C). Higher temperature levels mean enameled wires can operate reliably at higher temperatures for longer periods of time.

The operating temperature can be increased by 25-30 °C for each level of temperature classification, and the application range of enameled wires is expanded accordingly. The temperature classification of enameled wires at 240 °C is only lower than that of special R (220 °C) and 250 °C, which is much higher than that of H (180 °C), and is at the high-end position of the enameled wire temperature classification system.

5.2 Comparison of paint film materials

* * B grade paint film * * (PU, PE): polyurethane or polyester material, paint film thickness 5-20 μm, long-term use temperature 130 °C.

* * F-grade paint film * * (PEI): Polyesterimide material, paint film thickness 8-25 μm, long-term use temperature 155 °C.

* * H grade paint film * * (Pai): polyamide-imide material, paint film thickness 10-25 μm, long-term use temperature 180 °C.

* * N-grade paint film * * (Pai modified): Polyamide-imide modified material, long-term use temperature 200 °C.

* * 240 °C grade paint film * * (PI + Pai composite): polyimide + polyamide-imide composite paint film, film thickness 25-40 μm, long-term use temperature 240 °C.

Compared with conventional paint film, 240 °C grade paint film has a qualitative leap in heat resistance, dielectric strength, chemical stability, mechanical strength and so on.

5.3 Comparison of performance parameters

240°C enameled wire significantly outperforms conventional enameled wire on the following key performance parameters:

* * Dielectric breakdown voltage * *: 240°C enameled wire 8-15 kV, Class B enameled wire 4-6 kV, Class F enameled wire 5-7 kV, Class H enameled wire 6-8 kV.

* * Thermal aging life (200 °C test temperature) * *: 240 °C enameled wire > 20,000 hours, Class B enameled wire < 1,000 hours, Class F enameled wire about 4,000 hours, Class H enameled wire about 10,000 hours.

* * Chemical resistance * *: 240 °C enameled wire (PI) is resistant to strong acids, strong bases, solvents, oils and other media, H grade enameled wire (Pai) is resistant to general chemical media, and B/F grade enameled wire has poor chemical resistance.

* * Temperature range * *: 240 °C enameled wire -269 °C to +260 °C, H grade enameled wire -60 °C to +200 °C, B/F grade enameled wire -40 °C to +130/155 °C.

* * Cost * *: 240 °C enameled wire is 5-10 times that of conventional grade B enameled wire, 3-5 times that of grade F enameled wire, and 1.5-2.5 times that of grade H enameled wire.

5.4 Comparison of applicable working conditions

* * Class B enameled wire * * Suitable for: household appliances, low power motors, general-purpose transformers (operating temperature < 130°C).

* * Class F enameled wire * * Suitable for: general industrial motors, medium power transformers, air conditioning compressors (operating temperature < 155°C).

* * Class H enameled wire * * Suitable for: traction motors, generators, high power transformers, industrial pumps (operating temperature < 180°C).

* * 240 °C enameled wire * * Suitable for: aviation motor, traction motor, nuclear power main pump, downhole equipment, special military industry, high temperature sensor (operating temperature < 240 °C).

5.5 Cost Reasonableness Analysis of 240°C Enameled Wire

Although the initial procurement cost of 240 °C enameled wire is 5-10 times that of conventional enameled wire, its comprehensive cost rationality is significantly better than that of conventional enameled wire in high demand applications:

* * Advantage 1: Extended device life * *. Equipment with 240°C enameled wires has a design life of up to 20-30 years, while equipment with H-grade enameled wires typically has a design life of 10-15 years.

* * Advantage 2: Reduced maintenance costs * *. 240 °C enameled wire has high reliability at high temperatures, low equipment failure rate, and annual maintenance costs can be reduced by 50-80%.

* * Advantage 3: Increased power density * *. 240 °C enameled wire allows higher current density and power density, which can reduce the size of the equipment by 20-40%, indirectly reducing the overall cost of the equipment.

* * Advantage 4: Reduced energy consumption * *. 240 °C enameled wire has good resistance stability at high temperatures, low conductive loss, and long-term operation energy consumption can be reduced by 5-10%.

Considering comprehensively, 240 °C enameled wire has significant comprehensive cost advantages in aviation, nuclear power, military industry, rail transit, traction and other highly demanding fields.

VI. Model Selection Guidelines for Enameled Wires at 240°C

Proper selection is key to ensure successful 240°C enameled wire application. This section will introduce the selection method of 240 °C enameled wire systematically.

6.1 5 Key Factors in Model Selection

* * Factor 1: Operating Temperature * *. The actual operating temperature is the basis for selection. Class H (Pai) enameled wire can be selected when the operating temperature is ≤ 180 °C; Class N (Pai modified) enameled wire can be selected when the operating temperature is 180-220 °C; Class 240 °C (PI + Pai composite) enameled wire should be selected when the operating temperature is 220-240 °C. The safety margin of 10-15 °C should be reserved for selection.

* * Factor 2: Operating voltage * *. Select the film thickness according to the working voltage of the winding. Grade 1 film (25-32 μm) for low-voltage windings (< 1 kV); Grade 2 film (30-38 μm) for medium-voltage windings (1-10 kV); Grade 3 film (35-42 μm) for high-voltage windings (> 10 kV).

* * Factor three: conductor diameter * *. Determine the conductor diameter according to the winding design. LP Winding Wire 240°C enameled wire is available in full specifications from Φ 0.10-3.00 mm. The ultra-thin wire (Φ 0.10-0.30 mm) is suitable for high frequency small windings; the thin wire (Φ 0.30-1.00 mm) is suitable for general motor and transformer windings; the thick wire (Φ 1.00-3.00 mm) is suitable for high power windings.

* * Factor 4: Work environment * *. Consider the special requirements of the working environment such as chemical medium, radiation, humidity, etc. PI paint film with better chemical resistance should be selected for chemical corrosion environment; PI paint film should be selected for radiation environment (such as nuclear power) (excellent radiation resistance); PI paint film with good hydrolysis resistance should be selected for high humidity environment.

* * Factor 5: Industry Certification * *. Select according to the certification requirements of the application industry. Aviation applications should comply with AS 43701, NEMA MW 1000 certification; nuclear power applications should comply with IEEE 323, IEC 60780 and other nuclear power plant safety level certification; rail transit applications should comply with EN 50329, IEC 60310 certification; automotive applications should comply with ISO/TS 16949, IATF 16949 certification.

6.2 Recommended specifications for different applications

* * Application 1: Traction motor * *. PI + Pai composite paint film is recommended, the diameter of the conductor is Φ 0.50-2.00 mm, the thickness of the paint film is 30-38 μm, the elongation is ≥ 30%, and the temperature index is ≥ 240.

* * Application 2: Aviation motors * *. PI paint film is recommended, in line with AS 43701 certification, conductor diameter Φ 0.20-1.50 mm, film thickness 25-32 μm, ultra-light weight optional aluminum core 240 °C enameled wire.

* * Application 3: Nuclear main pump * *. PI paint film is recommended, in line with IEEE 323 certification, the conductor diameter is Φ 0.50-3.00 mm, the thickness of the paint film is 35-42 μm, and a life expectancy of 60 years and an irradiation dose of 10 Gy are required.

* * Application 4: Downhole equipment * *. PI + Pai composite paint film is recommended, the diameter of the conductor is Φ 0.30-1.50 mm, and the thickness of the paint film is 30-38 μm, which requires oil resistance and chemical corrosion resistance.

* * Application Five: High Temperature Sensor * *. PI paint film is recommended, the diameter of the conductor is Φ 0.10-0.50 mm, and the thickness of the paint film is 25-32 μm, which requires high precision and high stability.

6.3 Common Misunderstandings in Selection

* * Myth 1: The higher the temperature level, the better * *. 240°C enameled wire is not required for all applications. For applications with operating temperatures ≤ 180 °C, selecting H grade enameled wire can meet the requirements, and the cost is lower. Excessive temperature levels can lead to unnecessary cost wastage.

* * Myth 2: The thicker the paint film, the better * *. Increasing the thickness of the paint film will reduce the fill rate of the conductor, reduce the cross-sectional area of the winding, and affect the electrical performance. The appropriate film thickness should be selected according to the operating voltage, not blindly increased.

* * Myth 3: Ignore conductor materials * *. The conductor material (copper/aluminium/copper-clad aluminium) has a significant effect on the performance of the enameled wire. The aluminum core enameled wire is light in weight and low in cost, but has poor conductivity and weldability. Copper core enameled wire has good electrical conductivity and weldability, but it is heavy and costly. The conductor material should be selected according to the application requirements.

* * Myth 4: Ignore flexibility requirements * *. The 240°C enameled wire has a thicker film and is slightly less flexible than conventional enameled wire. For applications that require tightly bent or profiled windings, the model with a thinner paint film or the addition of a plasticizer should be selected.

* * Myth 5: Ignore certification requirements * *. Highly demanding industries such as aviation, nuclear power and rail transit have strict certification requirements, and suppliers and products with corresponding certification should be selected.

VII. Production quality control of 240 °C enameled wire

The quality control of 240 °C enameled wire is more stringent than that of conventional enameled wire, and a sound quality management system needs to be established.

7.1 Raw material quality control

* * Copper pole quality control * *:

• Copper purity ≥99.97%, oxygen content ≤10 ppm
• Resistivity ≤0.01724 Ω·mm²/m (20°C)
• Appearance without oxidation, without defects
• Batch traceability

* * PI resin quality control * *:

• Solid content 15-25%
• Viscosity 1,000-5,000 cP
• Molecular weight 50,000-150,000
• Residual solvent ≤1%
• Batch traceability

* * Pai resin quality control * *:

• Solid content 20-30%
• Viscosity 2,000-8,000 cP
• Glass transition temperature ≥270°C
• Batch traceability

7.2 Process Quality Control

* * Conductor pretreatment * *:

• Annealing temperature 400-500°C ±5°C
• Elongation after annealing 30-40%
• Copper wire surface contact angle after cleaning ≤30°

* * Coating process * *:

• Paint temperature 20-30°C ±1°C
• Paint Viscosity 1,000-5,000 cP ±5%
• Coating speed 5-30 m/min ±0.5%
• Paint film thickness online measurementAccuracy ±1 μm

* * Baking process * *:

• Baking temperature gradient setting meets process specifications
• Each stage Temperature control accuracy ±5°C
• Tension control 50-200 g ±5 g
• Baking atmosphere flow rate stable

* * Collection process * *:

• Take-upTension 30-150 g ±5 g
• Spool appearance, weight, marking meet standards
• Moisture-proof, pollution-proof packaging

7.3 Quality control of finished products

* * Electrical performance testing * *:

• Dielectric breakdown voltage: sampling inspection per batch
• Paint film continuity: 100% online detection
• Insulation resistance: sampling inspection per batch

* * Mechanical performance testing * *:

• Elongation: sampling inspection per batch
• Tensile strength: sampling inspection per batch
• Wear resistance: sampling inspection per batch
• Mandrel winding: sampling inspection per batch

* * Thermal performance testing * *:

• Heat shock: sampling inspection per batch
• Softening breakdown: sampling inspection per batch
• Thermal aging: periodic type test

Chemical performance test

• Solvent resistance: periodic type test
• Oil resistance: periodic type test
• Hydrolysis resistance: periodic type test

Appearance inspection

• Paint film color uniform and consistent
• No bubbles, impurities, particles
• No scratches, indentations
• Spool packaging intact

7.4 Typical failure modes for 240°C enameled wires

* * Failure 1: Paint film cracking * *. Reason: The paint film is too thick, the baking is inadequate, and the winding process is inappropriate. Prevention: Optimize film thickness and baking process to control winding tension.

* * Failure 2: paint film delamination * *. Reason: Insufficient interfacial adhesion of double-layer paint film. Prevention: Optimize the coating process using a special coupling agent.

* * Failure three: thermal aging failure * *. Reason: The operating temperature exceeds the temperature level of the paint film, and the operation is over-temperature for a long time. Prevention: Reasonable selection, reserve temperature safety margin.

* * Failure 4: Chemical corrosion failure * *. Reason: Insufficient chemical resistance of the paint film, chemical medium erosion. Prevention: Select the appropriate paint film material according to the working environment.

* * Failure 5: Mechanical damage fails * *. Reason: The paint film is damaged during winding, wire embedding and shaping. Prevention: Optimize the winding process using special tools.

VIII. Development trend of enameled wires at 240°C

As a high-end enameled wire product, the technology development of 240 °C enameled wire shows the following trends.

8.1 New Material Trends

* * Trend 1: Nano-modified paint film * *. Adding nanomaterials such as nano-SiO2 and nano-Al2O3 to the PI paint film can significantly improve the heat resistance, wear resistance, and thermal conductivity of the paint film, while reducing the thickness of the paint film. The nano-modified PI coating has an operating temperature of 260-280°C and is the next generation of upgraded products for 240°C enameled wires.

* * Trend two: fluoropolymer paint film * *. Polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FEP) and other fluoropolymer coatings have excellent high temperature resistance (260 °C), chemical resistance and weather resistance, and are optional materials for enameled wires above 240 °C. However, fluoropolymer films have poor adhesion and require special primers.

* * Trend three: peek film * *. Polyether ether ketone (peek) is a special engineering plastic. It has a glass transition temperature of 143 °C, a melting point of 343 °C, and a long-term use temperature of 260 °C. It has excellent mechanical strength, chemical resistance, and radiation resistance. Peek film is an emerging technology direction for 240°C enameled wires, but prices are currently high.

* * Trend 4: Waterborne paint film * *. Traditional PI paint films use organic solvents and have large VOC emissions. The research and development of water-based PI paint film and water-based Pai paint film reduces VOC emissions and meets environmental protection requirements, which is the sustainable development direction of the enameled wire industry.

8.2 New Process Trends

* * Trend 1: Online Quality Monitoring * *. Machine vision, X-ray thickness measurement, infrared thermal imaging and other technologies are used to achieve 100% online monitoring of film thickness, pinholes and thermal distribution to improve quality stability.

* * Trend two: intelligent production * *. Introduce industrial Internet, big data and artificial intelligence technology to realize intelligent optimization, predictive maintenance and flexible production of enameled wire production process.

* * Trend three: energy saving * *. Optimize baking oven structure, heat recovery system, baking temperature curve, reduce energy consumption by 20-30%.

8.3 New Application Trends

* * Trend 1: New Energy Vehicles * *. With the popularity of the 800V high-voltage platform for electric vehicles, the working voltage of the motor has been increased to 800V, and the dielectric strength requirements of enameled wires have been significantly improved. 240 °C enameled wires (especially high dielectric strength models) have broad application prospects in new energy vehicle drive motors.

* * Trend 2: Low-altitude economy * *. The low-altitude economy industries such as eVTOL (electric vertical take-off and landing aircraft) and drones are developing rapidly, and the demand for lightweight, high power density, and high reliability motors is surging. 240 °C enameled wires are ideal materials for low-altitude economic motors.

* * Trend three: energy storage * *. With the rapid development of large-scale energy storage systems, household energy storage, mobile energy storage, etc., the demand for inductors and transformers with high power density and high reliability has increased. 240 °C enameled wire has a large application space in the field of energy storage.

* * Trend 4: Robots * *. Industrial robots, humanoid robots, service robots, etc. have surged demand for servo motors with high power density, high dynamic response, and high reliability. 240 °C enameled wire is the preferred material for high-end robot motors.

8.4 Market prospects for 240°C enameled wires

With the rapid development of new energy vehicles, low-altitude economy, robotics, energy storage, aerospace and other emerging industries, the market demand for 240 °C special high-temperature resistant enameled copper wires will continue to grow. It is expected that the global 240 °C enameled wire market will grow at an average annual rate of 10-15% in 2025-2030, which is much higher than the 3-5% of conventional enameled wire.

LP Winding Wire, Essex Furukawa, Sumitomo Electric, etc. are the main suppliers in the 240 °C enameled wire market in China. As a leading special enameled wire manufacturer in China, LP Winding Wire can provide 240 °C enameled wire products with Φ 0.10-3.00 mm full specifications and UL/TÜV/AS 43701/IEEE 323 certification, which has a significant market competitive advantage.

IX. Common problems and solutions for 240°C enameled wires

9.1 Design Phase FAQs

* * Issue 1: Incorrect operating temperature assessment * *. This leads to low or high enameled wire temperature level selection. Solution: Establish an accurate working temperature assessment model, taking into account factors such as ambient temperature, load temperature rise, hot spot temperature, transient overload, etc.

* * Problem 2: Inappropriate choice of film thickness * *. Causes insufficient insulation strength or low conductor fill rate. Solution: Select the thickness of the paint film according to the working voltage, surge voltage, safety margin and other factors.

* * Problem 3: The conductor diameter does not match the thickness of the paint film properly * *. Causes difficulty in winding or degradation in electrical performance. Solution: Consider the overall coordination of the outer diameter of the copper wire, the thickness of the paint film, and the size of the winding.

9.2 Frequently Asked Questions at the Production Stage

* * Problem 1: Paint film bubbling * *. Reason: residual solvent in the paint, too high baking temperature, insufficient baking time. Solution: Optimize the lacquer preparation process and adjust the baking temperature curve.

* * Problem 2: Uneven film thickness * *. Causes: mold wear, fluctuating paint viscosity, unstable coating speed. Solution: Regularly check the mold, control the viscosity of the paint, and stabilize the coating speed.

* * Problem 3: Inconsistent color of paint film * *. Reason: uneven baking temperature, different lacquer lotions. Solution: Regularly calibrate the baking temperature and strengthen the batch management of lacquer.

9.3 Use Phase FAQs

* * Problem 1: The paint film cracks during the winding process * *. Cause: The paint film is too thick, the winding tension is too large, and the winding tool is worn. Solution: Select the appropriate film thickness, control the winding tension at 50-150 g, and replace the wear tool.

* * Problem 2: Paint film damage during wire embedding * *. Reason: improper groove insulation, unreasonable wire embedding process. Solution: Optimize the wire embedding process with suitable groove insulation.

* * Problem 3: Insulation resistance decreases after long-term operation * *. Causes: thermal aging of the paint film, moisture absorption, chemical erosion. Solution: Regularly detect the insulation resistance and replace the aged enameled wire in time.

* * Problem 4: Breakdown voltage decreases after high temperature operation * *. Cause: thermal aging of the paint film, local overheating. Solution: Optimize the thermal design of the equipment to avoid local overheating.

X. LP Winding Wire’s 240°C Enameled Wire Solution

10.1 LP Winding Wire Company Profile

LP Winding Wire is a leading global manufacturer of special enameled wire, specializing in the production of 240 °C special high temperature resistant enameled copper wire, 180 °C H grade enameled copper wire, 155 °C F grade enameled copper wire, 130 °C B grade enameled copper wire, paper wrapped wire, glass wire wrapped wire, Nomex paper wrapped wire, PI film wrapped wire and other series products. The company has an annual production capacity of 30,000 tons, UL, TÜV, CCC, CSA, AS 43701, IEEE 323 and other international certifications, and its products are exported to more than 50 countries and regions around the world such as North America, Europe, Asia, and the Middle East.

10.2 LP Winding Wire 240°C Enameled Wire Product Specifications

LP Winding Wire offers 240°C special high-temperature resistant enameled copper wire in the following specifications:

* * Ultra-fine line series * * (Φ 0.10-0.30 mm):

• Conductor Material: High-purity oxygen-free copper
• Paint Film Structure: PI+PAI composite
• Paint Film Thickness: 25-32 μm
• Elongation: ≥30%
• Applicable Temperature: 240°C class

* * Fine line series * * (Φ 0.30-1.00 mm):

• Conductor Material: High-purity oxygen-free copper
• Paint Film Structure: PI+PAI composite
• Paint Film Thickness: 30-38 μm
• Elongation: ≥30%
• Applicable Temperature: 240°C class

* * Thick line series * * (Φ 1.00-3.00 mm):

• Conductor Material: High-purity oxygen-free copper
• Paint Film Structure: PI+PAI composite
• Paint Film Thickness: 35-42 μm
• Elongation: ≥30%
• Applicable Temperature: 240°C class

10.3 LP Winding Wire 240°C Enameled Wire Core Benefits

* * Advantage 1: Full specification coverage * *. Φ 0.10-3.00 mm Full specification products to meet different application requirements.

* * Advantage 2: Fully certified * *. UL, TÜV, CCC, CSA, AS 43701, IEEE 323 and other international certifications.

* * Benefit 3: Industry-wide applications * *. Aviation, nuclear power, rail transit, traction, new energy vehicles, robots, energy storage and other industry-wide applications.

* * Strength 4: Global availability * *. Products are exported to more than 50 countries and regions around the world with localized technical support.

* * Advantage 5: Customized service * *. Provide customized paint film materials, film thickness, conductor specifications, and packaging solutions according to customers’ special needs.

10.4 LP Winding Wire Contact Information

• Official Website: https://www.lpwindingwire.com
• Sales Email: sales@lpwindingwire.com

XI. Summary

240 °C special high temperature resistant enameled copper wire is a key winding material for high-end motors, transformers, and electrical equipment. It has core advantages such as ultra-high temperature long-term stability, excellent electrical insulation performance, excellent chemical stability, wide temperature range adaptability, and high mechanical strength. Its PI + Pai composite paint film structure maintains stable operation at 240 °C continuous working temperature, and is the preferred material in high-end fields such as aviation, nuclear power, rail transit, traction, new energy vehicles, robots, and energy storage.

Correct selection is the key to a successful 240°C enameled wire application. Comprehensively consider the working temperature, working voltage, conductor diameter, working environment, industry certification and other factors to select the appropriate paint film structure, film thickness, conductor specifications, certification level. As the world’s leading specialty enameled wire manufacturer, LP Winding Wire is your trusted partner for full-spec, fully certified, industry-wide 240°C enameled wire solutions.

XII. Appendix A: Technical Data Sheet for Enameled Wire at 240°C

A.1 Electrical properties of 240°C enameled wire

PI + Pai composite paint film enameled wire dielectric breakdown voltage range 8-15 kV, paint film continuity every 100 meters 0-0.5 pinholes, insulation resistance 2,000 MΩ · m (20 °C), dielectric loss angle tangent 0.01 (1 kHz, 20 °C).

A.2 Mechanical properties of enameled wire at 240 °C

PI + Pai composite paint film enameled wire elongation 30-40% (soft state), 200-250 MPa tensile strength (soft state), 1 × d round rod winding without cracking, single scratch force 10 N.

A.3 Thermal performance of 240 °C enameled wire

The thermal shock of PI + Pai composite enameled wire is 240 °C × 30 min without cracking, the thermal aging temperature index is 240 (20,000 hours), and the softening breakdown temperature is 350 °C.

A.4 Chemical properties of enameled wires at 240°C

The PI + Pai composite paint film enameled wire is resistant to 20% sulfuric acid, 20% sodium hydroxide, acetone, toluene, engine oil, transformer oil and other common chemical media for 24 hours. There is no significant change in immersion.

XIII. Appendix B: 240°C Enameled Wire Application Cases

B.1 Case 1: Aerospace Starter Generator

An aerospace starter generator uses LP Winding Wire Φ 0.50 mm 240 °C enameled wire, the operating temperature is 220 °C, the power density is 8 kW/kg, the service life is 20 years, and the operation is stable and reliable.

B.2 Case 2: Nuclear main pump motor

The main pump motor of a nuclear power plant adopts LP Winding Wire Φ 1.50 mm 240 °C PI enameled wire, the operating temperature is 240 °C, the irradiation dose is 10 Gy, and the service life is 60 years, which meets the requirements of IEEE 323 certification.

B.3 Case 3: High-speed rail traction motor

A high-speed rail CR400AF traction motor uses LP Winding Wire Φ 0.80 mm 240 °C enameled wire, the operating temperature is 200 °C, the power density is 1.2 kW/kg, and the operating mileage is 3 million kilometers without failure.

B.4 Case 4: New Energy Vehicle Drive Motor

An 800V high-voltage platform NEV drive motor adopts LP Winding Wire Φ 0.63 mm 240 °C enameled wire, with a peak power of 250 kW, a power density of 6 kW/kg, and a CLTC working efficiency of 96.5%.

B.5 Case 5: Downhole oil drilling motors

An oil deep well drilling motor adopts LP Winding Wire Φ 0.40 mm 240 °C enameled wire, operating temperature 220 °C, well depth 6,000 m, oil and chemical resistance, stable and reliable operation.