Overview
IEC 60641-1:2007 - Pressboard and presspaper for electrical purposes - Part 1: Definitions and general requirements defines the classification, composition and general supply requirements for pressboard and presspaper used as electrical insulating materials. It sets out terms and definitions (for example pressboard, presspaper, calendered, pre-compressed, glazed), preferred thickness ranges, machineability expectations and marking/packaging requirements. This edition clarifies material categories and updates provisions from the previous edition (e.g., surface finish is no longer specified; fixed nominal thicknesses replaced by preferred thicknesses).
Key topics and requirements
- Classification: Types of pressboard and presspaper are grouped by composition and functional properties (see IEC 60641-1 Table 1). Examples include high-purity sulphate pulp types and cotton-containing mixtures.
- Composition: Materials shall be made entirely from vegetable fibres of high chemical purity and be free from extraneous material or adhesives. Reference to “sulphate wood pulp” includes equivalent modern pulps with comparable degree of polymerization.
- Dimensions (preferred thicknesses):
- Presspaper (mm): 0.075, 0.10, 0.13, 0.15, 0.18, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.80
- Pressboard (mm): 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0
- Machineability: Pressboard must be sheared; materials ≤ 3.0 mm should be punchable without ragged edges, following manufacturer recommendations.
- Finish and supply: Surface finish is agreed between purchaser and supplier. Packing must protect material during transport/storage and consignments must be legibly marked with manufacturer, type, nominal thickness, sheet size/roll width and weight.
- Editorial changes: Types B.6/P.6 replaced (designations retained) and B.7/P.7 deleted; surface finish removal; preferred thicknesses introduced.
Applications and users
IEC 60641-1 is relevant for:
- Manufacturers of pressboard and presspaper wanting to meet international definitions and general specification practices.
- Transformer, capacitor and motor designers selecting insulating materials (e.g., high-density presspaper for capacitors, mouldable pressboard for shaped components).
- Procurement and quality assurance teams specifying material type, thickness, marking and packaging for electrical equipment.
- Test labs and standards specialists cross-referencing material classification prior to application-specific testing (see IEC 60641-3 for detailed material specifications).
Practical applications include insulation in transformers, capacitors, oil-immersed equipment, hermetic motors and general electrical apparatus where mechanical strength, ageing resistance and dielectric properties are required.
Related standards
- IEC 60641-3 (all subparts) - Specifications for individual materials; referenced for tolerances and detailed material requirements.
Keywords: IEC 60641-1, pressboard, presspaper, electrical insulating materials, classification, preferred thickness, machineability, composition, transformer insulation.
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