Phenolic cotton cloth rod applied to transformers

Application of Phenolic Cotton cloth Rods in Transformers Phenolic cotton cloth rods (IEC:PFCC41 ) are mechanical st...

Application of Phenolic Cotton cloth Rods in Transformers

Phenolic cotton cloth rods (IEC:PFCC41 ) are mechanical structural insulation components used in transformers. Their primary functions are insulation, mechanical fastening, and vibration resistance. They are widely applied in both oil-immersed and dry-type transformers.

I. Material Characteristics

Phenolic cotton cloth rods are manufactured by impregnating cotton cloth with phenolic resin and then hot-press curing into laminated rods. They offer:
Good electrical insulation performance
High mechanical strength
Strong impact resistance
Better vibration absorption compared to fiberglass materials
Good oil resistance
Easy machinability (can be turned, drilled, and tapped)
Compared with G10 / FR4, phenolic cotton rods have better toughness but a lower temperature rating (typically Class B, 130°C).

II. Main Applications in Transformers

Insulating Tie Rods

Used in winding clamping structures to:
Secure core clamps
Fix upper and lower press plates
Withstand axial electrodynamic forces during short circuits
This is the most common application.

Structural Support Columns

Used to:Support windings，Maintain oil duct spacing，Fix end structures

Clamping Structure Components

Upper and lower press plate connecting rods
Insulated fastening bolts
Insulating positioning pins

Internal Insulation Supports in Oil-Immersed Transformers

Due to good oil resistance, they are suitable for:
Internal tank support components
Long-term oil-immersed environments

III. Applicable Transformer Types

IV. Comparison with Other Insulating Rod Materials

In terms of short-circuit impact resistance, phenolic cotton rods are still widely used due to their superior toughness.

V. Why Phenolic Materials Are Still Used in Transformers

Although phenolic is a traditional material, it retains several irreplaceable advantages inside transformers:
Excellent mechanical buffering capability (absorbs short-circuit forces)
Cost-effective
Excellent machinability
Electrical performance sufficient for distribution-level voltage
They are especially common in 10kV–35kV distribution transformers.

VI. Future Trends

Gradual replacement by epoxy fiberglass materials in higher voltage levels
Stable demand in medium- and low-voltage markets
Possible upgrade toward halogen-free and higher thermal-class systems under stricter environmental regulations