What Is Electrical Kraft Paper?
Electrical kraft paper is a type of cellulose-based insulation material made from high-purity, unbleached wood pulp. People use it in both electrical insulation kraft paper applications (like transformers and motors) and thermal insulation systems.
📌 All kraft paper supplied conforms to IEC 60641-1 Type B.3.1, widely accepted by transformer OEMs in EU and MENA.
Where Kraft Paper Is Used in Transformer Insulation
Electrical kraft paper plays a crucial role in transformer winding protection and thermal insulation. It supports:
- Layer and inter-turn insulation in oil-immersed transformers
- Conductor wrapping for HV and LV coils
- Slot and end-turn insulation
- Base material for DDP (Diamond Dotted Paper)
- Laminated pads and cushioning for structural support
📌 Used by over 30 transformer manufacturers worldwide.
Key Technical Properties of Kraft Insulation Paper
| Property | Typical Range |
|---|---|
| Thickness | 0.05 mm – 0.5 mm |
| Dielectric Strength (in oil) | ≥ 60 kV/mm |
| Thermal Class | A or E (up to 105–120°C) |
| Resin Compatibility | Yes (supports DDP lamination) |
| Moisture Content (max) | ≤ 7% |
| Surface Finish | Smooth or creped |
📌 Conforms to IEC 60641, tested for dielectric performance in mineral oil.
Types of Kraft Paper for Transformer Insulation
| Type | Description | Application |
|---|---|---|
| Electrical Grade Kraft | High-purity, oil-compatible | Layer & turn insulation |
| Crepe Kraft | Mechanically stretched paper for flexibility | Around corners & irregular windings |
| Laminated Kraft | Multi-layer pressed kraft for thickness | Structural padding or blocking |
| DDP Base Kraft | Kraft coated with resin for adhesion | HV coil winding with curing |
| B-Grade Kraft | Lower-cost cellulose paper | General wrapping & low-voltage use |
Visual & Handling Characteristics
Electrical kraft paper typically appears light brown to tan in color, with a smooth surface texture. Rolls are tightly wound and have a consistent thickness. This makes them good for CNC slitting, manual cutting, and automated wrapping systems. Creped kraft has a visible corrugation, offering greater flexibility during installation.
Supplied Formats
- Rolls: Standard width ~1000 mm (custom slit widths available)
- Sheets: Pre-cut lengths for turn insulation or end wrapping
- Special Types: DDP, crepe kraft, or laminated kraft on request
- Core Diameters: 52 mm / 76 mm standard
How to Select the Right Kraft Paper for Your Project
To choose the ideal kraft paper transformer insulation, consider:
✅ Voltage class → Higher voltage needs higher dielectric strength
✅ Position in winding → Layer vs turn insulation may need different thickness
✅ Curing needs → Use DDP-ready kraft for heat bonding
✅ Mechanical handling → Choose crepe kraft for complex geometries
✅ Export packaging → Request vacuum packaging or moisture barriers
Relevant Standards & Compliance
- IEC 60641-1: Paper and pressboard for electrical purposes
- ISO 9001: Quality management certification
- RoHS / REACH: Material compliance for EU
- 📌 Full SGS dielectric test report & material datasheet available on request
Export, MOQ & Logistics Information
| Factor | Details |
|---|---|
| MOQ | 300–500 kg (or 50 rolls for small orders) |
| Lead Time | 7–15 working days (depends on slit type) |
| Packaging | Vacuum foil wrap + inner kraft + outer carton |
| Export Experience | CIF / DDP to 30+ countries with full documents |
Conclusion – Invest in Reliable Transformer Kraft Paper
Choosing the correct transformer kraft insulation material is essential for system reliability, performance, and safety. When you design HV coils, oil duct channels, or layered insulation, use high-quality kraft paper. It offers dependable electrical insulation and lasts well with oil.
Call to Action
👉 Not sure which grade of kraft paper suits your transformer?
🔘 Request a Quote Now
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Email: jessie.feng@sidanm.com
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