Polywrapped Copper Winding Wires for Submersible Motors

Construction of Polywrapped Copper Winding Wire

The polywrapped copper winding wire employs a multi-layer film insulation system built directly over the copper conductor. The conductor is manufactured from 100% pure electrolytic CC grade copper, ensuring high electrical conductivity and consistent performance . Standard conductor diameters range from 0.4 mm to 2.5 mm, with larger sizes available up to 3.0 mm for higher-power motor applications .

The insulation consists of three sequentially wrapped film layers. The first layer, applied directly over the copper conductor, is polyester film. This layer establishes the foundation for the insulation system, providing excellent adhesion to the conductor and contributing high dielectric strength at the interface where electrical stress is most concentrated. The second layer is biaxially oriented polypropylene (BOPP) film in opaque white. BOPP film is produced by stretching polypropylene in both longitudinal and transverse directions, a process that aligns the polymer molecular chains along the plane of the film and dramatically improves its tensile strength, dielectric strength, and barrier properties . The third and outermost layer is transparent BOPP film, which provides additional dielectric protection and a smooth surface finish for ease of winding .

After all three films are wrapped helically over the conductor, the assembly passes through an in-line continuous heat shrinkage furnace. This thermal treatment seals the overlapping film edges together and shrinks the films tightly around the conductor, forming a cohesive, void-free insulation system . The finished wire is rated for working voltages up to 5 kV and exhibits 40% elongation of the insulated wire, ensuring the flexibility required for winding into motor stator slots . The polywrapped construction is waterproof and suitable for continuous immersion in water .

Manufacturing Process

The production of polywrapped copper winding wire begins with the drawing of copper rod to the required conductor diameter. The copper must meet electrolytic grade standards to ensure consistent conductivity and minimize impurities that could affect insulation adhesion. Following drawing, the conductor is annealed to restore the softness and flexibility lost during the drawing process, a critical step for submersible winding applications where the wire must bend tightly without cracking.

The annealed conductor is then cleaned to remove residual oils and oxides before insulation application. The film-wrapping process uses sophisticated wrapping heads that apply the polyester and BOPP films in a controlled helical pattern. Each layer is wrapped with precise tension and overlap to achieve uniform coverage and concentricity around the conductor . The wrapping speed and film tension are critical parameters that determine the insulation‘s dielectric consistency and mechanical integrity.

After wrapping, the conductor with its three film layers passes through an inline continuous heat shrinkage furnace. The furnace temperature is carefully controlled to activate the heat-seal properties of the BOPP films without degrading the polyester layer or the copper conductor. The heat treatment serves two purposes: it seals the overlapping film edges to prevent water penetration between layers, and it shrinks the films tightly around the conductor to eliminate air voids that could cause partial discharge under electrical stress .

Finished wire undergoes quality assurance testing that includes conductor resistance measurement, insulation thickness verification, and high-voltage withstand testing. The wire is rated for operation at temperatures up to 130°C, providing substantial thermal margin for submersible motor applications where winding temperature rise occurs under load .

African Pump Applications

Polywrapped copper winding wire serves submersible pump applications across the African continent, where borehole water extraction and industrial water management are essential infrastructure.

Waterman Pumps of India, whose products are distributed in African markets, specifies polywrap double-coated copper winding wire for its WB Series 8-inch water-lubricated submersible motors. These motors are designed for installation in 8-inch or larger water wells and are explicitly rewindable and repairable . The polywrapped stator winding enables operation with water lubrication, with maximum water temperature of 35°C and protection degree of IP68. The WB Series covers power ratings from 7.5 kW to 75 kW and is deployed in residential water supply, irrigation, fountains, industrial water systems, mining, oil and gas, dewatering, and firefighting applications .

Vega submersible borehole motors, supplied through South African distributor Pumps On Line, offer polywrapped winding wire as standard for their 6-inch water-filled motors. The Vega 6” series covers power ratings from 5.5 kW to 37.5 kW with maximum immersion depth of 350 meters and IP68 protection . The motor specification explicitly lists “Winding wire: Polywrapped / PVC winding available on specific demand,” confirming polywrapped as the standard construction . These motors are designed for reliable operation in wells, dams, canals, rivers, and boreholes across Southern Africa.

The African submersible pump market is supported by established repair and rewinding infrastructure. M Bond Pumps in Cape Town operates a fully equipped engineering workshop providing certified rewinding for industrial motors, including borehole and submersible pumps, with in-house testing capabilities to 6 bar . Cape Armature Winders (CAW) in the Western Cape specializes in the repair, maintenance, and testing of submersible pumps, serving municipal water and sanitation facilities including the City of Cape Town‘s submersible sewage pumps. CAW operates a dedicated submersible pump test facility with computerised test reports and test certificates issued for every repair . Pro-Logic Technologies in Nairobi, Kenya, provides motor rewinding and repair services for submersible pump motors, serving borehole drilling companies and water treatment plants across East Africa .

Cost Advantages

The polywrapped construction offers several cost advantages that make it particularly suitable for African submersible pump applications where both initial cost and long-term reliability must be balanced.

The primary cost advantage derives from the efficient manufacturing process. Film wrapping is a continuous, high-speed operation that produces consistent quality with minimal material waste. The raw materials—polyester film and BOPP film—are commodity products available at competitive prices, and the triple-layer construction achieves high dielectric strength with relatively thin total insulation wall thickness. This efficiency translates to lower wire cost per meter compared to extruded insulation systems of equivalent performance.

From a motor manufacturing perspective, the thin insulation wall enables higher slot fill factors. More copper can be accommodated in the same stator slot volume, improving motor efficiency and power density. For a given power rating, this allows manufacturers to produce smaller, lighter motors or to extract more power from existing designs. The polywrapped construction has replaced traditional PVC wires in many applications due to superior performance characteristics including less water absorption, higher temperature withstand, and lower leakage current .

For end users in Africa, the cost advantage manifests in extended motor service life and reduced maintenance requirements. The polywrapped insulation resists water absorption and maintains dielectric properties over extended periods of immersion. The rewindable design of motors using polywrapped wire allows for economical repair rather than replacement when electrical failure occurs, a significant advantage in regions where equipment replacement costs are high relative to repair labor. The established network of motor rewinding facilities across South Africa and East Africa  ensures that polywrapped submersible motors can be serviced locally, avoiding the time and expense of shipping equipment for repair.

Conclusion

Polywrapped copper winding wire provides a technically sound and economically efficient insulation solution for water-filled submersible motors across Africa. The triple-layer polyester and BOPP film construction delivers high dielectric strength, water resistance, and thermal capability up to 130°C. African pump brands including Waterman and Vega specify polywrapped winding as standard for their water-lubricated submersible motors, serving borehole water supply, irrigation, mining, and industrial applications. The cost advantages of efficient manufacturing, high slot fill factors, and local repair capability make polywrapped wire a practical choice for Africa‘s demanding water infrastructure requirements.