Pressboard is more than just a passive insulation layer—it’s a functional mechanical component inside transformer designs. Pressboard is important in many areas of oil-immersed and dry-type transformers. It supports windings and separates conductive elements.
1.Why Pressboard Matters in Transformer Construction
Pressboard provides a dual function:
Electrical insulation — isolates conductive layers and windings
Mechanical structure — reinforces the geometry of the transformer core
It integrates seamlessly with:
- Presspaper (for layer insulation)
- Crepe paper (for flexible wrapping)
- Epoxy laminates (for structural hardening)
Suitable for both:
- Oil-immersed transformers
- Dry-type cast resin transformers
This makes pressboard for transformers indispensable in medium and high-voltage designs.
2.Main Application Zones Inside a Transformer
Below is a breakdown of key areas where pressboard transformer insulation is used:
**Application Area**
**Pressboard Function**
– **Winding Cylinder**: Provides electrical barrier and structural support.
– **End Rings**: Controls axial movement and insulation gap.
– **Duct Spacers**: Maintains airflow and keeps winding separation.
– **Layer Insulation**: Acts as an electrical barrier between winding layers.
– **Structural Blocks**: Offers mechanical reinforcement inside the core and windings.
These zones require high dimensional precision and oil compatibility.
Forms of Pressboard Used
Pressboard can be processed into various shapes and configurations, such as:
- Flat sheets — cut to custom size for cylinder or layer assembly
- Pre-compressed molded rings and barriers — for structural use
- CNC-machined pressboard blocks — for core clamping or insulation reinforcement
- Punched / creased sheets — for slot insulation, arc barriers, frame cornering
Each form offers a tailored function for transformer geometry.
3.Assembly Techniques and Processing Methods
To fit different transformer types and voltage levels, pressboard undergoes:
- CNC shaping and grooving — for consistent slot and radius profiles
- Oil impregnation — enhances dielectric strength and longevity
- Epoxy lamination — used in areas requiring maximum mechanical strength
These processes ensure that pressboard maintains function under heat, pressure, and electrical field stress.
4.Material Compatibility and Safety
When sourcing electrical pressboard, ensure it meets the following:
Fluid compatibility — suitable for:
- Mineral transformer oil
- Silicone-based fluids
- Natural and synthetic ester oils
Standards compliance — look for:
- IEC 60641 for pressboard insulation paper
- RoHS / SGS for material safety and environmental compliance
Moisture behavior — sealed pressboard maintains low moisture absorption (<7%) and remains dimensionally stable
5.Conclusion & CTA
Pressboard transformer insulation is not just a simple barrier. It is a special material that helps with both electrical and mechanical functions in transformer design.
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