Diamond Dotted Paper (DDP) is one of the most essential insulation materials in the manufacturing of power and distribution transformers. Known for its excellent electrical strength, heat resistance, and uniform adhesive coating, DDP plays a vital role in ensuring the reliability and longevity of transformer windings. This article explores how Diamond Dotted Paper is produced, its technical characteristics, and its wide-ranging applications in transformer insulation systems.
Diamond Dotted Paper is a type of electrical insulation paper that has a diamond-shaped epoxy resin coating applied on both sides. It is primarily made from high-purity kraft insulating paper, which serves as the base layer. The diamond pattern is precisely distributed to ensure even adhesion and proper ventilation between transformer coil layers. When heated during transformer assembly, the epoxy resin softens and bonds the layers firmly, preventing movement and improving the mechanical stability of the windings.
The production of Diamond Dotted Paper involves several critical steps to ensure consistency, insulation performance, and mechanical strength:
1. Base Paper Selection: High-purity electrical kraft paper with low ash content and high dielectric strength is chosen as the substrate. This ensures excellent insulation and thermal stability.
2. Epoxy Resin Preparation: A specially formulated epoxy resin is used for coating. The resin must have high adhesion, proper curing characteristics, and excellent compatibility with transformer oil.
3. Precision Coating Process: Using advanced coating equipment, the epoxy resin is applied onto the paper surface in a precise diamond pattern . The coating must be uniform, with controlled thickness to maintain even adhesion.
4. Drying and Curing: After coating, the paper is dried in a controlled environment to ensure that the epoxy resin reaches a semi-cured state (B-stage), allowing it to bond during transformer coil winding.
5. Quality Inspection: The finished DDP undergoes multiple quality tests, including surface uniformity, coating adhesion, dielectric strength, and moisture content, to ensure every roll meets international insulation standards such as IEC 60641 or GB/T 5591.
Diamond Dotted Paper is primarily used as interlayer insulation between transformer windings. When the coil is heated during the transformer drying or curing process (typically around 90–120°C), the epoxy resin partially melts and bonds adjacent layers together. After cooling, the resin solidifies, forming a rigid structure that prevents displacement of the winding under mechanical stress.
Key applications include:
• Inter-turn insulation in high-voltage transformer coils.
• Layer insulation between copper or aluminum windings.
• Oil-immersed transformer insulation to ensure dielectric safety and mechanical strength.
• Dry-type transformer coils where vibration resistance and structural stability are critical.
Enhanced Adhesion and Stability: The epoxy coating ensures that the insulation layers remain fixed during operation, reducing the risk of short circuits caused by vibration or movement.
Excellent Electrical Properties: DDP maintains high dielectric strength even under elevated temperatures and in oil-immersed environments.
Improved Heat Resistance: Suitable for Class A and Class E insulation systems, ensuring reliable performance under continuous thermal load.
Smooth Coil Winding: The diamond pattern provides controlled adhesion points, preventing trapped air and improving heat dissipation.
Diamond Dotted Paper is an indispensable material for modern transformer insulation systems. Its precision manufacturing process, consistent epoxy coating, and superior bonding capability make it ideal for high-reliability electrical equipment. As global demand for energy-efficient and durable transformers continues to grow, high-quality Diamond Dotted Paper for transformer insulation will remain a key component in ensuring operational safety, long service life, and stable electrical performance.
