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Classification of Electrical Laminated Wood and Its Applications in Oil-Immersed Transformers Introduction In the d...

Classification of Electrical Laminated Wood and Its Applications in Oil-Immersed Transformers

Introduction

In the design and manufacturing of oil-immersed transformers, the reliability of the insulation system is the cornerstone of power grid safety. Electrical Laminated Wood, a high-performance composite made from premium birch or beech veneers bonded with specialized insulating resins under high temperature and pressure, has become an indispensable structural and insulating material. Its popularity stems from its exceptional mechanical strength, superior dielectric properties, and excellent compatibility with transformer oil.

I. Classification of Electrical Laminated Wood

Based on manufacturing processes, physical density, and specific application requirements, electrical laminated wood is primarily classified into the following categories:
By Physical Density
High-Density Laminated Wood (1.1–1.3 g/cm³): Produced under intense pressure, this grade offers maximum compressive and shear strength. It is typically used for core structural supports that must withstand extreme short-circuit electromagnetic forces.
Medium-Density Laminated Wood (0.9–1.1 g/cm³): This grade balances mechanical performance with oil absorption. The moderate density allows for better penetration of transformer oil, further enhancing the overall insulation reliability.
By Structural Shape
Standard Sheets/Planks: The foundational raw material used for fabricating various components.
Custom Machined Parts: Using advanced CNC technology, laminated wood is fabricated into complex geometries such as support blocks, pressure rings, and brackets to meet the intricate spatial requirements inside a transformer.
By Laminating Direction
Parallel Laminated: All veneers are layered with the grain running in the same direction, providing exceptional tensile strength in a specific orientation.
Cross Laminated: Veneers are layered with grains alternating at 90-degree angles, ensuring uniform mechanical strength in all directions and superior dimensional stability.

II. Core Applications in Oil-Immersed Transformers

Electrical laminated wood serves the dual role of “skeleton” and “shield” within the transformer:
1. Winding Clamping and End Support
During operation or sudden short-circuit events, windings generate massive axial electromagnetic forces. Laminated wood clamping plates, pressure rings, and trapezoidal blocks securely lock the coils in place, preventing insulation failure caused by mechanical displacement.
2. Lead Support and Fixturing
Internal leads require precise positioning to maintain electrical clearances. Laminated wood brackets and clamps not only secure the leads against vibration but also utilize their high dielectric strength to prevent flashovers between leads and the tank wall.
3. Core Support and Insulation
Components such as yoke insulation blocks and body supports are frequently made of laminated wood. Since its dielectric constant (approx. 3.0–4.0) is close to that of transformer oil (approx. 2.2), it ensures a more uniform electric field distribution, significantly reducing the risk of partial discharge (PD).
4. Insulating Fasteners
In high-intensity electric field zones where metal bolts are prohibited, insulating bolts and nuts made of laminated wood provide necessary clamping force while eliminating the risks of inductive heating and electrical arcing.

III. Manufacturer selection

As a premier manufacturer of transformer insulation materials, Xujue Electrical offers laminated wood solutions with several core advantages:
Premium Raw Materials: We strictly select high-quality birch veneers with fine texture and zero knots.
Advanced Processing: Utilizing vacuum drying and precision-controlled thermal pressing to ensure the material is bubble-free and resistant to delamination.
Precision Machining: Equipped with advanced CNC machining centers, we provide global customers with customized, highly complex insulation components.
High Reliability: Fully compliant with IEC international standards, our materials maintain dimensional stability in oil environments.

Conclusion

With its unique physical and electrical characteristics, electrical laminated wood provides a robust guarantee for the stable operation of oil-immersed transformers. Understanding these classifications and selecting a high-quality manufacturer is essential for ensuring the long-term safety of power equipment.