Insulation Pressboard Ultimate Guide

Insulation pressboard is a rigid cellulose-based material with density ranging from 1.15-1.35 g/cm³, offering superior dielectric strength (10-25 kV/mm) and thermal stability (up to 105°C continuous). This engineered material is essential for transformer, switchgear, and motor applications. This Insulation Pressboard Ultimate Guide will let you understand all the info of Insulation Pressboard.

Key Technical Specifications of Insulation Pressboard

1.      Density Grades:

    a.    Standard: 1.15-1.25 g/cm³ (IEC 60641-2)

    b.    High-density: 1.25-1.35 g/cm³ for critical applications

2.      Performance Characteristics:

    a.    Moisture content: <5%, (conditioned)

    b.    Compressive strength: 80-120 MPa

    c.     Oil absorption: 8-12%, by weight

Insulation Pressboard Types

Chinese manufacturers now produce five specialized pressboard types meeting diverse electrical insulation requirements, with density variations from 1.05-1.40 g/cm³ for different voltage classes.

1.           Standard Pressboard (SPB)

a.    Density: 1.10-1.20 g/cm³

b.    Applications: Low-voltage transformers (<33kV)

c.     Key feature: Cost-effective with 8-12kV/mm dielectric strength

2.           High-Density Pressboard (HDP)

a.    Density: 1.25-1.35 g/cm³

b.    Applications: 66-220kV power transformers

c.     Advantage: 25%, higher compressive strength than SPB

3.           Pre-Compressed Pressboard (PCP)

a.    Pre-compressed to 0.5-1.0mm thickness

b.    Reduces oil impregnation time by 40%,

c.     Ideal for automated transformer production

4.           Laminated Pressboard

a.    3-7 layer cross-bonded construction

b.    Improved dimensional stability

c.     Used in bushings and structural components

5.           Flexible Crepe Pressboard

a.    0.1-0.5mm thickness range

b.    180° bend capability without cracking

c.     Specialized for motor slot insulation

Advantages of Insulation Pressboard

Insulation pressboard offers three unbeatable advantages for electrical equipment manufacturers: superior dielectric strength (15-30kV/mm), exceptional thermal stability (Class A 105°C rating), and structural integrity under mechanical stress. Chinese manufacturers have perfected these properties through advanced cellulose processing techniques.

What Insulation Pressboard Consists Of

Premium pressboard contains 100%, sulfate wood pulp processed through multiple calendering stages. Chinese manufacturers use special softwood fibers (typically pine or spruce) that undergo:

l  12-stage purification removing lignin

l  Multi-roller compression at 120-150°C

l  Natural resin bonding (no formaldehyde) Key components: • Cellulose fibers (92-96%,) • Bound water (3-5%,) • Natural resins (1-3%,) Top-tier suppliers now add:

l  Nano-cellulose reinforcement (0.5-1%,)

l  Anti-oxidation additives

l  pH stabilizers (6.8-7.2 range)

Application of Insulation Pressboard:

Insulation pressboard serves as the structural backbone in high-voltage electrical equipment, with primary applications in power transformers (70%, of usage), bushings (15%,), and switchgear (10%,). Chinese manufacturers now produce application-specific grades meeting international standards with tighter tolerances than ever before.

1.      Power Transformers

a.    Barrier insulation between windings

b.    1.25-1.30 g/cm³ density for 66kV+ systems

c.     Laser-cut components with ±0.15mm precision

2.      Bushings & Insulators

a.    High-density 1.30-1.35 g/cm³ grades

b.    Oil-impregnated for 100+ kV applications

c.     CNC-machined with ≤0.5%, moisture content

3.      Motor & Generator Components

a.    Slot wedges and phase separators

b.    Flame-retardant UL94 V-0 versions

c.     Pre-compressed for vibration resistance

What thickness insulation Pressboard should I use

The optimal pressboard thickness depends entirely on your voltage class and application. Here's what Chinese manufacturers typically recommend:

‌Standard Thickness Guidelines‌

1.      Low Voltage (≤1kV):

a.    0.5mm for coil separators

b.    1.0mm for phase barriers

2.      Medium Voltage (1-36kV):

a.    2mm for transformer winding insulation

b.    3mm for bushing supports

3.      High Voltage (36-550kV):

a.    5mm+ for main insulation barriers

b.    8mm for structural components

‌Key Selection Factors‌

l  Dielectric requirements: Add 0.5mm safety margin above calculated needs

l  Mechanical loads: Thicker boards (3mm+) for high vibration areas

l  Oil impregnation: Thinner boards (1-2mm) impregnate faster

l  CNC machining: 0.1mm tolerance boards for precision parts