Enamelled Copper Wire (EC)

Enamelled Copper Wire

Enamel copper wire is an electromagnetic wire formed by uniformly coating an insulating paint film on the surface of a high-purity copper conductor and curing it at high temperature. Enamel copper wire is the core material of electromagnetic components such as motors, transformers, and inductors. Its insulation layer combines high insulation, temperature resistance, and mechanical strength, making it one of the most widely used types of wires in the field of power electronics.

Core Features

Conductivity: Copper core conductivity ≥ 58.5 × 10 ⁶ S/m (IACS 100%), resistivity ≤ 0.017241 Ω·mm²/m (20 °C).
Insulation: The breakdown voltage of the paint film is ≥ 5kV (thickness 5-50 μ m), and the dielectric strength is>100kV/mm.
Temperature resistance: The temperature resistance level covers 130 ° C (Class B) to 240°C (Class C), and some special wires can reach up to 300 °C.
Flexibility: The paint film has strong adhesion and can withstand winding with a bending radius of ≤ 2 times the wire diameter.

Classification

Enamel coated copper wire can be classified according to insulation paint type, temperature resistance level, conductor structure, and functional characteristics. Specifically, as follows:
According to the type of insulation paint

Type

Polyester enameled wire (PEW): Low cost, temperature resistance of 130 ° C (Class B), used for general motors and small transformers (such as household electric motors).
Polyurethane enameled wire (UEW): Excellent direct welding performance (self soldering at 380~420 ° C), no need for paint scraping, used for relay coils and electronic components.
Polyimide Enamel Wire (PIW): Temperature resistant to 240 ° C (Class C), radiation resistant, used in aerospace and high-temperature motors (such as electric vehicle drive motors).
Polyesterimide Enamel Wire (EIW): Temperature resistant to 180 ° C (H-grade), resistant to refrigerant corrosion, used for air conditioning compressors and industrial frequency converters.
Self-adhesive Enameled Wire: The surface of self-adhesive enameled wire is coated with thermoplastic resin, bonded after heating, and used for high-frequency inductors without immersion process.

Conductor Structure

Round line: standard cross-section (diameter 0.02~6mm), accounting for over 80% of the market.
Flat wire: rectangular cross-section (thickness 0.5-5mm, width 2-20mm), used for high-efficiency motors (such as Tesla Model 3 drive motors).
Leeds line: Multiple ultra-fine insulated wires twisted together (single wire diameter ≤ 0.1mm) to reduce high-frequency eddy current losses, used for wireless charging and 5G base stations.

Functional Characteristics

High frequency and low loss type: Adding nano alumina (Al ₂ O3) filler to reduce dielectric loss (tan δ ≤ 0.005).
Corona resistant type: polyamide imide+polytetrafluoroethylene composite paint film, extending the life of high-voltage motors.
Self lubricating type: The surface is coated with fluorine to reduce winding friction (friction coefficient ≤ 0.15).

Manufacturing Process

The production process of enameled copper wire includes copper material processing, painting, baking, cooling, and testing. Specifically, as follows:
Preparation of Copper Conductors
Drawing: Electrolytic copper rod (purity ≥ 99.99%) is drawn through multiple passes to the target diameter with an accuracy of ± 0.001mm.
Annealing: Heat to 450-600 ° C under nitrogen protection to restore the elongation of copper (soft line ≥ 30%).
Painting Process
Multi layer coating:
Primer: Epoxy modified resin to enhance adhesion (thickness 2-5 μ m).
Topcoat: Functional insulating paint (such as polyester imine), with a single layer thickness of 3-8 μ m, applied 6-12 times in total.
Coating Method
Mold coating: accuracy ± 0.5 μ m, suitable for ultra-fine wires (diameter ≤ 0.05mm).
Felt coating: Low cost, suitable for conventional wires (diameter 0.1-3mm).
Baking and Curing
Vertical baking oven: segmented temperature control (200~450 ° C), solvent evaporation and resin cross-linking are completed simultaneously.
Horizontal baking furnace: high-speed production (line speed ≥ 60m/min), temperature uniformity ± 2 ° C.
Cooling and Post-processing
Water cooling: Quickly cool down to below 50 ° C to prevent thermal aging of the paint film.
Wax coating: Apply microcrystalline wax (0.1-0.3 μ m) on the surface to improve wear resistance (reduce wire breakage rate by 50%).
Quality Inspection
Pinhole detection: High voltage spark test (3-5 kV), 100% online detection, allowing pinholes ≤ 3 per kilometer.
Scratch resistance test: Scratch with a steel needle (pressure of 2-5N), and the paint film does not peel off.
Thermal shock test: After bending around the axis (axis diameter=wire diameter × 2) and baking (150 ° C × 1h), there are no cracks.

Enamelled Copper Wire List

Diameter	Performance Characteristics
0.080-0.3000 mm	It has excellent paint film toughness and locked-rotor impedance. It is suitable for both manual and automatic winding and inserting.

Enamelled Copper Wire Application

Enamel coated copper wire has the advantages of thin insulation layer (<50 μm), high space utilization, and wide temperature resistance range (130~300 °C), and can be widely used in the following scenarios:
Household Electric Appliances
Air conditioning compressor: Polyester imine enameled wire (resistant to R410A refrigerant), diameter 0.8-1.2mm.
Washing machine motor: Polyester enameled wire (Class B), cross-sectional area 0.3~0.8mm ², cost sensitive design.
Automotive Industry
Drive motor: Flat wire enameled copper wire (H-grade), with a cross-sectional area of 2-10mm ², and a slot filling rate increased by 30% (such as Tesla Model Y).
Car charger (OBC): self-adhesive enameled wire, simplified dipping process, increased production efficiency by 20%.
Industrial Equipment
Variable frequency motor: corona resistant enameled wire (Class C), used for high-voltage frequency converters (voltage ≥ 3kV).
Welding machine transformer: Polyester imine wire (Class F), temperature resistance of 155 ° C, vibration resistance.
New Energy and Electricity
Wind turbine: C-grade high-temperature resistant enameled wire (cross-sectional area ≥ 50mm ²), resistant to salt spray corrosion.
Photovoltaic inverter: Leeds line (200 strands x 0.1mm), reducing high-frequency losses (increasing efficiency by 2%~5%).
Electronics and Communication
Wireless charging coil: Leeds wire structure (single wire diameter 0.05mm), operating frequency 6.78MHz, efficiency ≥ 85%.
5G base station transformer: high-frequency low loss enameled wire (dielectric loss tan δ ≤ 0.003), supporting millimeter wave transmission.
EADS
Onboard motor: polyimide+polytetrafluoroethylene composite paint film, temperature resistant to 300 ° C, used for auxiliary power unit (APU).
Satellite attitude control: ultra lightweight enameled copper wire (conductor diameter ≤ 0.1mm), reducing weight by 40%.