Aluminum Strip for Transformer Winding

Transformer aluminum strip is a key raw material for manufacturing transformer windings. It is a strip material obtained by rolling aluminum ingots. It has high technical requirements in terms of conductivity, burrs and edge curling, side bending, surface quality, and more. As an important electrical material, transformer aluminum strip plays an indispensable role in power transmission and distribution systems, especially as a conductive material in the high and low voltage windings of dry-type transformers.

During the operation of the transformer, the aluminum strip mainly undertakes the function of current transmission, while also participating in the electromagnetic conversion process of the transformer. It is one of the core materials affecting the transformer's performance.

The electrical and thermal conductivity of aluminum is second only to copper, making it one of the best conductive materials among conventional metals. Due to the much higher price of copper compared to aluminum, and with the rapid development of aluminum smelting technology, the output, quality, and purity of aluminum have been greatly improved. The price of aluminum materials is also gradually decreasing, making aluminum strip increasingly a trend to replace copper strip in transformer winding applications.

Common grades of aluminum strip used for transformer windings include 1050, 1050A, 1060, 1070, 1070A, and 1350. These grades belong to pure aluminum or low-alloy aluminum alloys, characterized by high purity and good electrical conductivity.

Among them, the 1060 grade aluminum strip, with an aluminum content of over 99.6%, is a commonly used series in the aluminum strip family. Its production process is relatively simple, the technology is mature, and it offers a significant price advantage compared to other high-end alloy aluminum plates. The 1350 grade aluminum strip is a high-purity aluminum specifically designed for electrical applications, featuring higher conductivity and more stable electrical performance.

Features of Transformer Winding Aluminum Strips

• Burr-Free: The aluminum strips undergo precision processing, resulting in an extremely thin thickness and a smooth, flat surface without any burrs, ensuring safety and reducing losses.
• Round Edge Design: The edges of the aluminum strips are specially treated to form rounded edges, preventing mechanical damage or electrical insulation issues during use, enhancing safety and reliability.
• High Conductivity: Made from high-purity aluminum, the strips exhibit excellent electrical conductivity, which can effectively reduce energy loss and improve transformer efficiency.
• High-Purity Material: The aluminum strips have extremely high purity, typically using aluminum with a purity of over 99.6%, ensuring excellent electrical performance and stability, suitable for demanding electrical applications.
• Good Flexibility: The aluminum strips undergo full annealing treatment, providing them with good flexibility, making them easy to process and shape in transformer windings, while also enhancing service life and performance stability.
• High Strength Standards: While ensuring high conductivity, the mechanical strength of the aluminum strips meets high standards, capable of withstanding various stresses and loads during manufacturing and operation, ensuring long-term stable operation of the transformer.

Electrical Conductivity of Aluminum Foil Strips for Transformers

• 1050: Better than 60% IACS.
• 1060: Better than 61.5% IACS.
• 1070: Better than 62.7% IACS.
• 1350: Better than 62% IACS.

Transformer Winding Aluminium Strips Specifications

Transformer Aluminum Strip Surface Quality Control Standards

As a professional transformer aluminum strip manufacturer, Haomei Aluminum always adheres to the principle of "quality first, " implementing strict surface quality control throughout the entire production process to ensure that the products possess excellent insulation performance and long service life.

Edge Quality:

• Burr-Free: Burr height ≤ 0.03–0.05 mm (to prevent insulation damage).
• Rounded Edges: Improves winding efficiency and safety.

Tolerance:

• Thickness: ±0.01–0.08 mm (varies with thickness range).
• Width: ±0.1–2.0 mm (the narrower the strip, the tighter the width tolerance).
• Certification: Complies with GB/T 3190-1996 (Chemical Composition) and YS/T 713-2009 (Electrical Performance).

Surface Cleanliness Control

We have strict standards for the surface cleanliness of aluminum strips:

Each coil must be cleaned and treated with electrostatic dust removal equipment before leaving the factory;

Ensuring the aluminum strip surface is free of oil stains and dust to avoid affecting subsequent insulation treatment and performance stability.

Strictly Prohibited Surface Defects

To ensure the safety and continuity of transformer windings, we strictly control the appearance quality of the product:

Corrosion, oil spots, cracks, split edges, bubbles, holes, and other defects that affect structural integrity and performance

Edge curling, burrs, and uneven edges that affect winding and insulation integrity

Any form of joints is prohibited. Each coil of aluminum strip must be joint-free to maintain continuous and reliable electrical performance.

Acceptable Minor Defects (Strictly Controlled Range)

Under the premise of not affecting the final use of the product, we allow a minimal amount of the following minor surface marks, which must meet strict internal grading standards:

Scattered, shallow indentations, slight scratches or scuff marks

Slightly embedded metallic or non-metallic particles that do not affect function

Mild roller marks and slight orange peel textures, but must be within acceptable range and not affect insulation coating or winding appearance

Transformer Aluminum Strip Surface Treatment

To improve the insulation performance and corrosion resistance of transformer aluminum strips, special surface treatments are often required:

Insulation Coating Treatment

A layer of insulating material, such as polyester or polyimide, is applied to the aluminum strip surface to enhance interlayer insulation performance.

Passivation Treatment

A passivation film is formed on the aluminum strip surface through chemical treatment to enhance corrosion resistance.

Anti-Oxidation Treatment

A special anti-oxidation layer is formed on the surface of the aluminum strip to prevent oxidation during long-term use.

Anti-Sticking Treatment

Special treatment is performed on the surface of the aluminum strip to prevent sticking during the winding process.

These surface treatment processes can be selected according to specific usage environments and requirements to ensure that transformer aluminum strips can operate reliably under various working conditions.

Technical Advantages of Aluminum Strip for Transformer Windings

Excellent Electrical Conductivity

Aluminum’s conductivity is only behind silver, copper, and gold, ranking fourth among commonly used metals. While aluminum has a conductivity of about 37.7×10^6 S/m, compared to copper's 58×10^6 S/m, it is sufficient to meet the needs of most transformers.

Through proper design of the aluminum strip’s cross-sectional area and winding structure, aluminum-wound transformers can achieve electrical performance comparable to copper-wound transformers. For transformers, performance depends not only on materials, but also significantly on structural design and manufacturing technology.

Good Thermal Conductivity

Transformers generate heat during operation. Good thermal conductivity is another key feature of transformer aluminum strips. Aluminum's thermal conductivity is 237 W/(m·K), lower than copper’s 397 W/(m·K), but significantly higher than other common metals.

This good thermal conductivity helps dissipate heat during transformer operation, keeping it within normal operating temperatures, and improving reliability and lifespan. Especially under high-load and high-temperature conditions, aluminum strips help reduce hot spot temperatures and slow insulation aging.

Significant Weight Reduction Advantage

Aluminum has a density of about 2.7 g/cm³, much lower than copper's 8.96 g/cm³, giving aluminum-wound transformers a significant weight advantage. For the same capacity, aluminum-wound transformers are typically 30%-40% lighter than copper-wound ones.

This lightweight feature brings multiple benefits: lower transportation costs, easier installation, reduced structural load, and easier maintenance—ideal for weight-sensitive applications like high-rise buildings and mobile substations.

Obvious Cost Advantage

Aluminum’s price is significantly lower than copper’s, giving aluminum-wound transformers a clear cost advantage. Market data shows that aluminum typically costs about one-third as much as copper.

This cost benefit applies not only to material procurement but also to overall transformer manufacturing: lower density means less material is needed for the same electrical performance; good workability lowers processing costs; abundant aluminum resources make prices more stable.

Good Corrosion Resistance

Aluminum quickly forms a dense aluminum oxide film in air, effectively preventing further oxidation and corrosion. In most natural and general industrial environments, aluminum windings have good corrosion resistance.

In contrast, copper may corrode in specific environments (e.g., those with sulfides or chlorides). Therefore, aluminum-wound transformers may offer better long-term reliability in certain conditions.

Excellent Workability

Transformer aluminum strips are usually supplied in the O temper (soft), offering excellent ductility and processability. This condition allows easy bending, winding, and forming to meet complex winding structure needs.

Specifically, the processing advantages of transformer aluminum strip include: good elongation and tensile strength, meeting standard processing requirements (stamping, stretching); high formability for various shapes; weldability via gas welding, atomic hydrogen welding, and contact welding; and good capability to withstand pressure processing and bending.

Aluminum Strips for Transformers Chemical Composition

1050 O Aluminum Strips Chemical Composition

1060 O Aluminum Strips Chemical Composition

1070 O Aluminum Strips Chemical Composition

1350 O Aluminum Strips Chemical Composition

Transformer Aluminum Strip Thickness Tolerance

Transformer Aluminum Strip Width tolerance

Transformer Aluminum Strip Burrs and collapse

Types of Aluminum Strips for Transformers

Transformer Aluminum Strip 1050 O

The 1050 aluminum foil strip contains 99.5% aluminum, offering excellent conductivity and flexibility. It is fully annealed in the O temper, making the foil softer and easier to process. It is commonly used in transformer windings and is suitable for applications requiring high conductivity and good ductility.

The 1050 O aluminum strip is one of the most commonly used materials in transformers. It is frequently used as support material in transformer windings, which helps to reduce transformer losses and improve performance.

The thickness of the 1050 O aluminum strip used in transformers generally ranges from 0.1mm to 1mm. It is available in single or double-layer structures, which can effectively reduce magnetic leakage in coils and enhance insulation performance.

Transformer Aluminum Strip 1060 O

The 1060 aluminum foil strip has an aluminum content of up to 99.6%, offering excellent electrical conductivity and high corrosion resistance. In the O temper, 1060 aluminum foil is softer and easier to shape, making it suitable for winding transformer coils, especially where strict electrical and mechanical performance is required.

1060 O aluminum alloy has good plasticity but lower strength compared to other alloys. It is mainly used in various high and low voltage electrical devices, such as transformer windings.

Transformer Aluminum Strip 1070 O

The 1070 aluminum foil strip is based on high-purity aluminum with 99.7% aluminum content. It has outstanding conductivity and good flexibility and durability. The 1070 O temper foil can form stable coil structures during transformer winding, making it suitable for transformer designs that require higher conductivity and ductility.

The 1070 O aluminum foil for transformer windings can be used in dry-type transformers, oil-immersed transformers, and reactor windings.

The 1070 O aluminum foil for transformer windings has excellent heat dissipation properties, and does not increase the temperature rise of the coil during long-term operation, thus extending the coil's service life. Using 1070 O aluminum foil for transformer windings can reduce the cost of batch manufacturing transformers by 15%.

Transformer Aluminum Strip 1350 O

The 1350 aluminum foil strip is a high-purity aluminum foil with an aluminum content exceeding 99.5%, widely used in transformer windings. The 1350 O temper foil, after annealing, has excellent plasticity and flexibility, meeting the high conductivity and mechanical stability requirements for transformer winding materials.

The 1350 O aluminum foil for transformer windings is widely used in the transformer industry, including oil-immersed transformers and dry-type transformers.

The 1350 O aluminum foil for transformer windings is available in both bare and coated types. The bare type is mainly used as winding material for oil-immersed transformers, while the coated type is primarily used as interlayer insulation material.

Transformer Winding Aluminium Strip Superior to Copper

Advantages and Disadvantages of Copper Strip for Transformers

Advantages of Copper Strip:

Excellent conductivity, low resistance loss, high efficiency

High mechanical strength and hardness, good structural stability

High thermal conductivity, good heat dissipation

High melting point, good high-temperature stability

Good connectivity, not easily oxidized

Long service life

Disadvantages of Copper Strip:

High cost, both in material and processing

Heavy weight, increasing transportation and installation costs

Limited resources, subject to market fluctuations

High energy consumption in recycling

Advantages and Disadvantages of Aluminum Strip for Transformers

Advantages of Aluminum Strip:

Low cost, significantly cheaper than copper strip

Lightweight, easy to transport and install

Abundant resources, stable supply

Good corrosion resistance in most environments

Good recyclability, low energy consumption for recycling

Good processability, easy to form into various shapes

Disadvantages of Aluminum Strip:

Lower conductivity, higher resistance loss

Lower mechanical strength, especially for pure aluminum

High thermal expansion coefficient, prone to deformation

Low melting point, poor high-temperature stability

Poor connectivity, easily oxidized

Shorter service life

Application Selection Recommendations:

• For small transformers, low-power transformers, and cost-sensitive applications, aluminum strip is recommended to reduce cost and weight.
• For large transformers, high-power transformers, and critical electrical equipment where high reliability is required, copper strip is recommended to ensure performance and longevity.
• For transformers in special environments such as high temperature, high humidity, or highly corrosive conditions, choose materials based on specific environmental requirements.

When selecting materials, a comprehensive technical and economic analysis should be conducted, considering initial investment, operating cost, service life, and maintenance cost.

Application Scenarios of Transformer Aluminium Strips

Main Material for Large Transformer Coils

Aluminium strips are primarily used for winding transformer coils, helping to improve the efficiency and reliability of transformers. Their properties make them suitable for various types of transformers, including distribution transformers and power transformers.

• Dry-Type Transformers: Due to their light weight and corrosion resistance, aluminium strips are the preferred choice for windings.
• Oil-Immersed Transformers: The usage rate is continuously increasing, as they save costs and reduce maintenance.
• Distribution: Used in transformers up to 4 MVA.

Applications in Solar and Power Industry

Aluminium strips, as conductive materials for the high and low-voltage windings of dry-type transformers, are suitable for use in the power industry, solar energy, and other fields.

Other Industries that Use Transformer Aluminium Strips

Practical Application Cases

Dry-Type Transformer Applications

Dry-type transformers are the main application area for aluminum strip windings, especially in places with high fire protection, explosion-proof, and environmental requirements. Aluminum strip for dry-type transformers features high conductivity, softness, smooth surface, and no burrs, making it an ideal material.

Power Transformer Applications

Aluminum strip wound transformers are also widely used in power systems, especially in medium and low voltage distribution transformers. Compared to traditional copper-wound transformers, aluminum-wound ones offer high efficiency, low losses, energy savings, compact size, light weight, strong overload capacity, and safe and reliable operation.

Special Environment Applications

Aluminum strip wound transformers perform well in special environments: humid conditions, high temperatures, corrosive environments, mobile and portable applications.

New Energy Applications

Aluminum strip wound transformers also have broad application prospects in new energy fields such as wind power, solar power, and energy storage systems.

Working Principle of Transformer Aluminum Strip

Transformer aluminum strip primarily utilizes the electrical conductivity of aluminum to form a current path in the transformer. When alternating current passes through the aluminum strip, it generates an alternating magnetic field, achieving energy conversion and transmission through electromagnetic induction. Compared with traditional copper strip, aluminum strip offers lower cost and lighter weight while maintaining good electrical conductivity. The working principle of transformer aluminum strip is based on the use of aluminum’s conductivity to form a current path. When alternating current flows through the aluminum strip, it creates an alternating magnetic field that enables power conversion and transmission via electromagnetic induction. Compared to copper strip, aluminum strip offers reduced cost and weight with good conductivity.

Transformer Aluminum Strip Selection Method

Select Aluminum Alloy Grade Based on Transformer Type

Different types of transformers have varying performance requirements for aluminum strips. The appropriate alloy grade should be selected according to the specific application scenario:

Dry-Type Transformers

Typically, 1060 or 1070 grade aluminum strips are selected. These materials have high purity and good electrical conductivity, meeting the performance requirements of dry-type transformers.

Oil-Immersed Transformers

1050 or 1060 grade aluminum strips can be used. These materials have good corrosion resistance and workability, making them suitable for use in oil-immersed environments.

Special Transformers

For example, high-frequency transformers and pulse transformers may require specialized electrical aluminum strips such as 1350, which offer higher conductivity and more stable electrical performance.

Select Specifications Based on Technical Parameters

When selecting transformer aluminum strips, the specifications should be chosen based on specific technical parameter requirements:

• Thickness selection: The thickness of the aluminum strip should be determined based on the transformer's rated capacity, operating voltage, and winding structure. Generally, the larger the capacity and higher the voltage, the thicker the aluminum strip required.
• Width selection: The width of the aluminum strip should be based on winding design requirements and winding processes, while also considering the capacity of winding equipment.
• Conductivity requirements: Select aluminum strips with appropriate conductivity based on the transformer's efficiency requirements and loss limitations. Generally, the higher the conductivity, the lower the winding loss—but the higher the cost.
• Mechanical performance requirements: Choose aluminum strips with appropriate tensile strength and elongation based on the winding process and structure to ensure no breakage or excessive deformation occurs during winding.

Cost-Performance Analysis and Long-Term Cost Consideration

When selecting transformer aluminum strips, one should not only consider the initial purchase cost, but also conduct a comprehensive cost-performance analysis and long-term cost evaluation:

Cost Factor Analysis

Initial cost: Compare quotations from different suppliers, including material cost, processing cost, and transportation cost.

Operating cost: Consider the impact of aluminum strip conductivity on transformer losses and calculate the energy consumption cost during long-term operation.

Maintenance cost: Consider how the quality of aluminum strips affects transformer maintenance frequency and cost.

Service life: Evaluate how the quality and performance of aluminum strips affect transformer lifespan, and calculate the total lifecycle cost.

Reliability value: Consider the potential value brought by the improved reliability and safety of the transformer due to high-quality aluminum strips.

By comprehensively considering these factors, one can choose the most cost-effective transformer aluminum strip product to achieve long-term economic and technical benefits.

Transformer Aluminum Strip Production Process

Raw Material Preparation

Select aluminum ingots with appropriate purity, perform accurate ingredient calculation, and carry out impurity removal and preheating treatment to ensure impurity content ≤0.02%. High-quality raw materials are the foundation for producing high-quality transformer aluminum strips.

Melting and Refining

Add pretreated aluminum ingots and alloying elements into the melting furnace and heat to 700–800℃ for melting. Stir uniformly for 30–45 minutes. Use gas blowing and filtration to remove impurities and gases, and precisely control the molten aluminum temperature to prepare for subsequent casting.

Casting and Ingot Treatment

Pour the molten aluminum into molds to form ingots, control the cooling rate to avoid internal stress and defects, and perform homogenization treatment to improve internal structure and ensure uniform grain structure.

Rolling and Heat Treatment

Heat the ingot to 550–580℃ for hot rolling. Further reduce thickness through cold rolling to the target thickness. Perform final annealing on the cold-rolled aluminum strip to obtain the desired O temper (soft condition), improving flatness and surface quality.

Finishing and Surface Treatment

Slit the aluminum strip to the required width, chamfer and deburr the edges, clean the surface to remove oil and impurities, and perform surface treatments such as passivation or coating as needed to enhance corrosion resistance and insulation performance.

Quality Control and Inspection

Conduct comprehensive quality inspections on incoming raw materials, key process parameters during production, and finished products. Tests include chemical composition analysis, conductivity testing, mechanical property testing, dimensional measurement, and visual inspection. Establish a complete quality traceability system.

Processing and Treatment of Transformer Aluminium Strips

Processing of Transformer Aluminium Strips

• Raw Material Preparation and Heating: First, the aluminium ingots are placed in a furnace and heated. The furnace temperature gradually increases to an appropriate range to melt the aluminium. Alloying elements are added during the melting process to remove impurities and enhance the purity and performance of the aluminium.
• Casting and Billet Cutting: After impurities are removed from the molten aluminium, it is cast into aluminium billets, which are then cut into aluminium plates of the specified thickness for further rolling processes.
• Rough Rolling: The cut thick plates are sent to the cold rolling machine for rough rolling. The cold rolling process gradually reduces the thickness of the aluminium plates and initially adjusts the material’s mechanical properties to meet the requirements for the subsequent hot rolling.
• Hot Rolling and Finishing: The rough-rolled aluminium plates are sent to the hot rolling mill for further processing. The hot rolling process, conducted at higher temperatures, effectively enhances the ductility and toughness of the aluminium strips, resulting in finished strips that meet the specifications.
• Annealing: After rolling, the aluminium strips undergo an annealing process. Annealing involves heating the material to a certain temperature and maintaining it for a period to relieve internal stresses, improve ductility, flexibility, and corrosion resistance, ensuring the stability of the aluminium strip’s performance.
• Cutting and Shaping: The edges of the annealed aluminium strips are trimmed to ensure accurate dimensions and smooth edges.
• Packaging and Shipping: Finally, the finished transformer aluminium strips undergo quality inspection and are coiled and packaged according to customer requirements. Once the packaging is complete, the aluminium strips are safely transported to the designated location for use.

Manufacturing Considerations

When selecting aluminium strips for transformer windings, factors such as alloy grade, thickness, width, and edge treatment must be considered to meet the specific transformer design requirements. Proper annealing and surface treatment can further improve performance and extend service life.

Transformer aluminium strips offer a combination of electrical efficiency, mechanical strength, and economic feasibility, making them the preferred material for transformer manufacturing.