Insulating Materials for Transformers

Here, we will discuss the insulating materials commonly used for transformers, including fiberglass laminates, insulation films, glass fiber cloth/ mesh/tape, and insulation paper etc.

A. Insulating Materials for Dry Type Transformers:

insulating materials for dry type transformers

1. Fiberglass Laminated Sheets like 3240 epoxy sheets are often used for iron core insulation.

2. Insulation films such as PET film and polyimide film are widely used for interturn insulation and the insulation cylinders.

3. Prepreg DMD, made of electrical grade non-woven cloth bonded with PET film then impregnated with epoxy resin, often used for low voltage layer insulation.

4. Glass fiber mesh is used for the reinforcement of winding or layer insulation.

5. Alkali-free fiberglass cloth is used for layer insulation in transformers.

6. Alkali-free fiberglass unidirectional binding tapes are used for binding transformer iron core and fixating winding as well as interturn insulation.

7. NHN insulation paper, a composite paper made of two-layer Nomex plus polyimide film in between, most used for interturn or layer insulation.

8. Sheet Molding Compound (SMC), made of assembled rovings impregnated with unsaturated polyester resin, used for non-encapsulated high-voltage coil pads.

B. Insulating Materials for Oil-immersed Transformers:

insulating materials for oil-immersed transformers

1. Cable paper is used for interturn and layer insulation.

2. Crepe paper is used for electrostatic ring and lead binding.

3. The electrical crepe paper tube is mainly used as insulation wrapping material for the oil-immersed transformer leads.

4. The phenolic laminated paper tube with good dielectric properties, is suitable for transformer oil as insulation structural parts for electrical equipment in dry environments.Temperature resistance: E class 120℃.

5. Diamond dotted paper(DDP) is used for layer insulation in distribution transformers as well as winding fixation.

6. Electrical pressboards are used for insulation cylinders, pads, bracing bars, and surrounding barriers and iron core insulation.

7. Electrical laminated wood is used as lead supports, supporting boards and pressure plates.

8.The electrical white cloth tape, made of cotton yarns, is widely used for general binding of coils on electrical appliances.

9.The electrical polyester high/low shrinkable tape has a certain degree of heat resistance and insulation, widely used as coil binding materials for motors, electrical appliances, and transformers.

10.The polyester unidirectional binding tape is suitable for binding transformer iron core.