Politubes manufactures a wide range of spiral-wound insulating tubes specifically designed for the transformer industry. These tubes are used for cable insulation, tie-rod protection, and clamping bolt insulation within magnetic cores.

Solutions for Oil-Filled Transformers

For oil-immersed transformers, we supply spiral-wound tubes made from smooth or micro-creped kraft paper. These materials ensure excellent impregnation capability and deliver increased durability, elasticity, flexibility, and mechanical strength during assembly.

Solutions for Resin Dry-Type Transformers

For cast-resin dry-type transformers, we produce spiral-wound tubes in Mylar®, special DMD laminates, and Nomex® (for operating temperatures up to 220°C). These tubes are used to insulate tie rods and cables exposed to high temperatures, such as in traction transformers.

Why Tie-Rod Insulation Is Critical in Transformers

In transformers, tie rods keep the core laminations under constant compression. Without proper electrical insulation, stray flux generated by several windings may close through the air gap and pass through the tie rods, inducing eddy currents and potential differences. This phenomenon poses a significant risk to the reliability and operational safety of the transformer.

Politubes spiral-wound tubes are engineered specifically to prevent these issues, ensuring effective electrical insulation and long-lasting protection.

Key Advantages of Politubes Spiral-Wound Tubes

Compared to traditional rolled tubes, our spiral-wound solutions offer clear and measurable benefits:

• Easy and efficient installation
• Reduced scrap, lower costs, and improved production efficiency
• Elimination of jamming or telescoping during insertion
• Custom manufacturing with lengths ranging from 20 to 6000 mm
• Very tight dimensional tolerances
• Longer operational lifetime
• Perfectly round geometry, with no internal or external overlaps, ensuring uniform impregnation and consistent insulation
• Available in multiple wall thicknesses (0.3 – 2 mm) for an optimal balance between electrical insulation and mechanical strength