Detailed Explanation of Insulation Materials Used in Transformers

By azhe July 5th, 2025 316 views

In the design and manufacturing process of transformers, selecting appropriate insulation materials is crucial. High-quality insulation materials not only ensure the safe operation of transformers but also effectively extend their service life and enhance overall performance. Below is an in-depth look at several commonly used transformer insulation materials and their characteristics.

1. Paper Insulation Materials
1. Kraft Paper:

Characteristics: Good mechanical strength and electrical properties, easy to process.
Applications: Widely used in oil-immersed transformers as insulation between windings.
2. Crepe Paper:

Characteristics: Soft and elastic, suitable for wrapping complex shapes.
Applications: Often used to wrap conductors or winding ends, providing additional mechanical protection and insulation.
2. Resin-Based Insulation Materials
1. Epoxy Resin:

Characteristics: Excellent heat resistance, mechanical strength, and chemical stability; forms a solid after curing.
Applications: Primarily used in casting processes for dry-type transformers to ensure internal structural stability and insulation performance.
2. Polyester Resin:

Characteristics: Good electrical properties at a relatively low cost.
Applications: Used as insulating coatings or encapsulation materials in some small transformers.
3. Mica Products
1. Phlogopite Mica:

Characteristics: Maintains good electrical insulation even at high temperatures, resistant to acids and alkalis.
Applications: Commonly used in high-voltage motors and specialized transformers as insulating components.
2. Synthetic Mica:

Characteristics: Superior performance compared to natural mica, especially outstanding in high-temperature environments.
Applications: Used to make high-voltage insulation barriers or bushings.
4. Glass Fiber Reinforced Materials
1. Fiberglass Cloth:

Characteristics: High strength and excellent heat resistance; when combined with resins, significantly improves composite material performance.
Applications: Commonly used in dry-type transformers as insulation layers between windings.
2. Fiberglass Mat:

Characteristics: Loose structure with good air permeability, suitable for applications requiring efficient heat dissipation.
Applications: Often used to fabricate ventilation ducts or as auxiliary insulation layers.
5. Liquid Insulating Media
1. Mineral Oil:

Characteristics: Low cost, excellent insulation properties, and cooling capabilities.
Applications: Standard cooling and insulating medium in most oil-immersed transformers.
2. Synthetic Ester Oil:

Characteristics: Fire-resistant and environmentally friendly, suitable for fire-sensitive areas.
Applications: Used as a substitute for mineral oil, particularly in environmentally sensitive regions or where special safety requirements exist.
3. Silicone Oil:

Characteristics: Exceptional high-temperature stability and aging resistance.
Applications: Ideal choice for specialized transformers or use in high-temperature environments.
6. Gas Insulating Media
1. Sulfur Hexafluoride (SF₆):

Characteristics: Extremely high dielectric strength, non-flammable, and non-toxic.
Applications: Used as an insulating gas in enclosed high-voltage switchgear and certain transformers.
2. Air:

Characteristics: The most common natural insulating medium, lowest cost.
Applications: Fundamental medium in dry-type transformers and air-insulated switchgear.

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