Polyimide Film Coated Copper Wire for Submersible Motors

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Thermal Performance

Polyimide film insulation offers a temperature rating of 220°C (Class C), with the wire capable of operating continuously at this temperature while maintaining its electrical and mechanical properties. This thermal capability is documented in Chinese standard JB/T 5331-2011, which specifies the requirements for particular types of aromatic polyimide tape wrapped round copper wire for submersible motors. The polyimide film structure provides stability across a wide temperature range, with products tested and verified for operation from -40°C to 200°C.

The combination of polyimide film with FEP coating adds further thermal and chemical resilience. FHF films (FEP/Polyimide/FEP) have been tested to meet and exceed the requirements of JB/T 2226-96, with dielectric strength reaching 168 MV/m—34% higher than the standard requirement. The FEP coating provides an additional barrier against water ingress, oil penetration, and chemical attack.

Dielectric and Electrical Properties

The breakdown voltage of polyimide film coated copper wire significantly exceeds that of conventional enameled wires. For a 70μm thickness FHF film, the dielectric strength reaches 168 MV/m, translating to substantial voltage withstand capability. The standard polyimide film coated wire typically achieves breakdown voltages exceeding 7,000V, making it suitable for voltage classes up to 10kV.

The volume resistivity at elevated temperatures (200°C) is maintained at 1.4 × 10¹⁴ Ω·m, ensuring consistent insulation resistance even under high-temperature operating conditions. This high electrical stability is critical for submersible motor applications where even small leakage currents can lead to insulation degradation and eventual motor failure.

Mechanical Strength and Flexibility

The polyimide film exhibits exceptional tensile strength of approximately 165 MPa, with elongation at break reaching 86%. This combination of high strength and flexibility is essential for the wire winding process, enabling the conductor to be formed into coils without cracking or damaging the insulation. The mechanical properties also provide resistance to abrasion during motor assembly and handling.

Dimensional Specifications

Round Conductors

Polyimide film coated round copper wire for submersible motors is available in diameters from 1.0mm to 5.0mm. Standard specifications include diameters corresponding to:

• Φ1.50mm to 5.00mm

• SWG 6# to 17#

• AWG 5# to 15#

The insulation can be applied in 2, 3, or 4 layers depending on the voltage rating and application requirements. Standard insulation thickness options include 0.36mm, 0.54mm, 0.63mm, and 0.72mm, with custom thicknesses available for specific applications.

Rectangular Conductors

For higher current applications, polyimide film coated rectangular conductors are also available. These are manufactured using high-purity oxygen-free copper extruded to the required dimensions, with the polyimide film applied using a spiral wrapping process with overlap exceeding 50%, followed by high-temperature sintering.

The rectangular conductor construction offers improved space utilization in motor slots, higher current-carrying capacity, and reduced AC losses compared to round conductors of equivalent cross-sectional area.

Manufacturing Process

Conductor Preparation

The manufacturing process begins with the selection of high-purity oxygen-free copper. For round conductors, the copper is drawn to the required diameter through precision dies. For rectangular conductors, the copper is extruded to achieve the specified dimensions, with tight tolerances maintained throughout the process.

Polyimide Film Application

The polyimide film is applied through a wrapping process where the film tape is wound around the conductor at a controlled angle. For FHF films (FEP/Polyimide/FEP), the double-sided FEP coating allows for heat fusion bonding during the sintering process. The wrapped film is then passed through a sintering oven where the FEP layers melt and fuse to create a seamless, hermetic insulation layer.

The sintering process is critical to the performance of the finished wire. The fusion of the FEP layers creates a continuous, void-free insulation structure that resists water penetration, oil absorption, and chemical attack. The resulting insulation is both oil-proof and waterproof, essential for submersible motor applications.

Key Applications

Electric Submersible Pumps

Electric Submersible Pumps (ESP) are one of the primary applications for polyimide film coated copper wire. ESPs are deployed in hydrocarbon-producing wells, where they pump produced fluids from within the well bore to the surface. These systems are typically disposed at the end of production tubing and experience well temperatures exceeding 180°C in high-temperature formations.

The polyimide film insulation system addresses the specific challenges of ESP applications. The thermal stability ensures the motor operates reliably at high downhole temperatures, while the oil resistance and water resistance protect the insulation from the well fluids. As noted in Halliburton patent literature, Kapton polyimide film is recognized for having the highest dielectric strength of any wire insulation currently available.

Downhole Oilfield Motors

Beyond ESPs, polyimide film coated wire is used in other downhole motor applications. These motors operate in conditions that would rapidly degrade conventional enamel insulation systems. The polyimide film’s ability to withstand both the thermal and chemical stresses of downhole environments makes it the preferred choice for these applications.

Submersible Pumps for Water and Industrial Applications

Submersible motors used in groundwater extraction, municipal water supply, and industrial process applications also benefit from polyimide film insulation. The material’s resistance to weak acids, alkalis, and salts makes it suitable for a wide range of water quality conditions. FHF films in particular offer superior resistance to moisture, solvents, and corona discharge.

High-Voltage and Inverter-Duty Motors

The high dielectric strength of polyimide film insulation makes it suitable for high-voltage motors operating at 4kV to 10kV. The insulation system also provides enhanced corona resistance, making it appropriate for inverter-fed motor applications where variable frequency drives generate steep voltage fronts and high electrical stress.

Standards Compliance

Polyimide film coated copper wire for submersible motors is manufactured in compliance with:

• JB/T 5331-2011: The Chinese mechanical industry standard for particular types of aromatic polyimide tape wrapped round copper wire for submersible motors. This standard covers H-class and below submersible motors and similar oil-filled special motors, as well as submersible pump cable insulation.

• MW 63-C: The NEMA standard for polyimide film insulated magnet wire.

• GB/JB/IEC: Additional compliance with relevant Chinese and international standards.

Quality and Packaging

The wire is tested for continuity of insulation, dimensional conformity, and breakdown voltage. Packaging is typically provided on wooden spools, with standard spool dimensions accommodating weights up to 100kg per spool. Custom packaging solutions are available for customer requirements.