Electrical Laminated Wood in Transformer Insulation Systems: Applications, Standards and Manufacturing Process

As power systems continue to develop toward higher voltage levels, larger capacity and greater reliability, transformer insulation systems are subject to increasingly demanding requirements for electrical performance, mechanical strength and dimensional stability. In oil-immersed transformers, in addition to commonly used materials such as electrical insulation paper and pressboard, electrical laminated wood is also an important structural insulation material.

Electrical laminated wood is not ordinary wood. It is a specialized electrical insulation material manufactured through controlled drying, bonding, hot pressing and densification processes. With its combination of good electrical insulation, mechanical strength, dimensional stability and machinability, electrical laminated wood is widely used for transformer blocks, spacers, support components, clamping components and other insulation structures.

For transformer manufacturers, laminated wood provides both electrical insulation and mechanical support. Therefore, material quality and machining accuracy can have a direct impact on the stability and reliability of the internal transformer structure.

Why Is Electrical Laminated Wood Suitable for Transformers?

The interior of a transformer is not simply an insulation environment. During operation, windings, cores and clamping structures are exposed to mechanical stresses while maintaining strict insulation distances and electrical performance requirements.

Electrical laminated wood is manufactured by drying, sorting, bonding, stacking and hot-pressing wood veneers to form a dense and uniform laminated structure. These processes improve the mechanical properties and dimensional stability of the material while retaining the advantages of wood-based materials, including relatively low weight and good machinability.

As a result, laminated wood can provide both electrical insulation and mechanical support in transformer structures.

This is particularly important for oil-immersed transformers, where internal insulation materials may remain in contact with transformer oil for extended periods. Therefore, the material needs to provide stable insulation performance as well as suitable dimensional stability and long-term reliability under the actual operating conditions.

Main Applications of Electrical Laminated Wood in Transformers

In transformer manufacturing, electrical laminated wood is generally not used simply as a large-area insulation material. Instead, it is machined into different shapes according to the internal structure and design requirements of the transformer.

For example, laminated wood can be machined into blocks and spacers for transformer windings. These components help maintain the designed distances between windings while withstanding mechanical loads.

In core and winding clamping structures, laminated wood can be used as insulating blocks or support components, providing mechanical support while helping maintain electrical insulation between metallic structures.

For large transformers, various customized insulation components may also be manufactured according to engineering drawings, including rings, positioning components, support parts, pressing blocks, and components with holes, slots or complex profiles.

As a result, the purchasing requirements of modern transformer manufacturers are increasingly moving from simply purchasing laminated wood sheets toward an integrated solution involving:

Laminated Wood Material + Precision Machining + Customized Insulation Components

This trend places higher demands on both the material manufacturing capabilities and CNC machining capabilities of electrical insulation material suppliers.

IEC 61061 and GB/T 20634: Important Standards for Electrical Laminated Wood

As the application of electrical laminated wood in electrical equipment continues to expand, product quality needs to be controlled according to applicable standards and technical specifications.

For international markets, electrical non-impregnated densified laminated wood is mainly covered by the IEC 61061 series.

Among these standards, IEC 61061-1:2006 covers the definitions, designation and general requirements for non-impregnated densified laminated wood for electrical purposes. The IEC 61061 series also includes relevant test methods and specifications for different forms of laminated wood products.

In China, the corresponding national standard system is the GB/T 20634 series, covering definitions and general requirements, test methods, as well as specifications for boards and rings made from wood veneers.

In actual procurement, transformer manufacturers may refer to IEC and GB/T standards while also specifying their own requirements for material grades, mechanical properties, electrical properties, dimensional tolerances and inspection procedures based on transformer design requirements.

Electrical Laminated Wood Manufacturing Process

The production of electrical laminated wood involves multiple processes to ensure good electrical insulation, mechanical strength and dimensional stability. The basic manufacturing process is:

Wood Selection → Veneer Drying → Sorting & Cutting → Adhesive Application → Layer Assembly → High-Temperature & High-Pressure Hot Pressing → Cooling & Stabilization → Thickness Calibration → Inspection → Packaging

In general, suitable wood veneers for electrical insulation applications are first selected, dried and sorted. Adhesive is then uniformly applied to the veneer surfaces, and multiple layers are stacked according to the required product thickness. The veneers are subsequently hot-pressed under controlled temperature and pressure to form a dense and stable laminated structure.

After hot pressing, the material is cooled and stabilized before thickness calibration and dimensional processing. Finally, the finished laminated wood is inspected for appearance, dimensions and relevant performance requirements before packaging.

For applications such as transformer blocks, spacers and insulation structural components, the laminated wood can be further processed through sawing, drilling, milling and CNC machining according to customer drawings.

From Laminated Wood Sheets to CNC-Machined Transformer Insulation Components

A typical machining process is:

Laminated Wood Sheet → Cutting → Thickness Calibration → CNC Milling → Drilling → Slotting → Chamfering → Dimensional Inspection → Final Inspection

For example, a standard laminated wood sheet can be CNC-machined into a customized transformer insulation component with multiple holes, slots and special profiles.

For transformer manufacturers, this approach can reduce secondary processing requirements, improve dimensional consistency and support efficient batch production.

What Should You Consider When Selecting Electrical Laminated Wood?

For transformer manufacturers, selecting laminated wood should involve more than simply comparing prices.

First, the intended application should be clearly identified. Different blocks, spacers, clamping components and structural insulation parts may have different mechanical load and dimensional requirements.

Next, the required dimensions and machining method should be determined. For standard sheets, customers can provide length, width and thickness. For machined components, CAD drawings or detailed technical drawings are recommended.

Other important considerations include:

Material density
Moisture content
Mechanical strength
Electrical insulation performance
Dimensional stability
Compatibility with transformer oil, where applicable
Machining accuracy
Dimensional tolerances

For oil-immersed transformers, material compatibility with transformer oil should be considered according to the actual operating environment.

If CNC machining is required, machining tolerances, material allowance and final dimensional requirements should also be considered during material selection.

Therefore, a complete laminated wood purchasing specification generally includes:

Material Standard + Material Grade + Dimensions + Quantity + Application + Machining Requirements + Inspection Requirements

Electrical Laminated Wood Is Moving Toward Customized Solutions

In the past, electrical laminated wood was primarily purchased as standard-size sheets. With the development of transformer and electrical equipment manufacturing, however, customer requirements are increasingly shifting from simply purchasing raw materials toward obtaining integrated insulation solutions.

For electrical insulation material suppliers, having a laminated wood production line alone may no longer be sufficient to meet all customer requirements. Material production, dimensional control, machining, quality inspection and customized manufacturing according to customer drawings are becoming increasingly important capabilities within the electrical insulation supply chain.

Especially for large transformers, special-purpose transformers and high-voltage electrical equipment, insulation materials need to meet not only basic electrical requirements but also the structural and mechanical requirements of the equipment.

As a result, suppliers capable of providing material manufacturing + customized machining + technical support are better positioned to provide long-term support to transformer and electrical equipment manufacturers.

Xujue Electrical: Electrical Insulation Materials for the Transformer Industry

As a professional manufacturer of electrical insulation materials, Xujue Electrical has extensive experience serving transformer, motor and other electrical equipment manufacturers.

The company provides electrical laminated wood sheets according to customer application requirements and supports customized machining based on customer drawings. These materials can be used for transformer blocks, spacers, support components, clamping components and other structural insulation parts.

When requesting a quotation for electrical laminated wood, transformer manufacturers are encouraged to provide product dimensions, quantity, application position, applicable standards and machining drawings. This enables the supplier to select the appropriate material and develop a suitable machining solution based on the actual application.

As the global electrical equipment industry continues to develop, electrical laminated wood will remain an important material for transformer insulation systems and structural insulation applications. For material manufacturers, continuously improving material consistency, machining accuracy and customized service capabilities will be increasingly important for meeting the requirements of next-generation electrical equipment manufacturing.