TECHNICAL ARTICLE

Product characteristic and application of DDP insulation paper

2020-09-02 17:04  |  By: ZTELEC  |  85click

Diamond dotted paper (DDP) insulation paper is an insulating material with special modified epoxy resin in the form of rhombus on electrical insulating paper. The products are widely used in the interlayer insulation and interturn insulation of oil-immersed power transformer. When used, the coating layer starts to melt at a certain temperature during the drying process of the coil, producing adhesion, and starts to solidify with the increase of temperature, so that the adjacent layers of the winding can be reliably bonded into a fixed unit. The bonding strength of the epoxy resin is sufficient to prevent the displacement of each layer of the winding during short circuit, thus ensuring the long electrical and mechanical properties of the insulation structure.

Because the resin coating of diamond dotted paper (DDP) is in the shape of dots, it ensures the oil immersion and the gas discharge in the insulating material, and effectively avoids corona and local discharge, thus ensuring the safety and reliability of the insulating structure. It can also be used as insulation layer for cable shield and corona proof material for high voltage motor and electric appliance.

It should be stored in a dry, clean and ventilated place not exceeding 35°C. It should not be close to fire sources or central heating. The storage period should be 12 months without direct sunlight. It was heated to 90°C±5°C, kept for 3 hours, then heated to 125°C±5°C, and cured for 6 hours.

With power cable paper as the substrate and composite epoxy resin as the adhesive, the DDP paper is printed on the substrate by the equipment to form two-sided rhombic adhesive paper. It is then baked, dried and rolled into a two-sided rhombic adhesive insulating paper.

DDP paper has good insulation and machinability. When the paper is heated, the glue melts, bonds the windings together and maintains tension. It is mainly used as a key insulating material for foil coils and non-paint coils in transformers and other electrical appliances.

Heat resistance of insulating material: As the motor is inevitably heated by loss during operation, the insulating material used must have good heat resistance. The heat resistance of insulating material directly determines the allowable temperature rise of the motor. Insulation material is divided into seven classes according to heat resistance, and each grade corresponds to a certain limit of service temperature below which the insulating material can be used for a long time without affecting its performance. In addition, insulation materials should also have good thermal conductivity and greater heat capacity.

As for large motor coil, we often hope that the linear expansion coefficient of insulation material can be close to conductive material to avoid insulation fracture during thermal expansion and cold shrinkage .

Mechanical properties of insulation materials: The insulation of coils and windings will be affected by various mechanical stresses in the process of wrapping, forming and loose packing as well as motor operation, so the corresponding mechanical properties of insulation materials are proposed, such as tensile, compressive, bending, shear, impact strength and so on. If the mechanical property of insulating material is very poor, it is easy to be affected by the mechanical force, and make the electrical property significantly reduced. There are other requirements for insulating materials, such as less hygroscopicity; Good resistance to acid, alkali and oil; It does not contain acid or other easily ionized substances; And it is easy to process and so on.

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