Aluminum conductive materials used in transformers can be categorized by thickness into aluminum foil and aluminum strip. Neither is inherently superior; the key difference lies in matching the transformer's capacity, winding structure, and heat dissipation requirements. The crucial distinction is in the thickness threshold and application scenario, not the name itself.
Aluminum foil, due to its thinness and excellent flexibility, is suitable for tightly wound small windings, such as those in small dry-type transformers and low-voltage windings of high-frequency transformers. Its advantage is maximizing winding space utilization, reducing volume, and meeting the conductivity requirements of low voltage and low current. However, its disadvantages are also obvious: lower mechanical strength and weak tear resistance, making it unsuitable for high-current, high-tension winding scenarios. Furthermore, the thinner the foil, the higher the precision requirements of the manufacturing process, necessitating strict control of burrs and thickness tolerances to avoid affecting insulation performance.
Aluminum strip (thickness > 0.2mm, common range 0.2-3.0mm), with its superior mechanical strength, has become the preferred choice for medium and large transformers, especially suitable for high-voltage and high-current windings. Its thickness provides better current carrying capacity and tensile strength, making it less prone to deformation and tearing during winding, able to withstand higher tension, and offering superior heat dissipation, effectively reducing temperature rise during transformer operation. Furthermore, the thickness tolerance control of aluminum strip is relatively relaxed, resulting in lower production costs and suitability for mass production.
The core alloy selection for transformer aluminum strip focuses on two types of industrial pure aluminum: 1050 and 1060 aluminum strip. Both belong to the 1-series of pure aluminum and possess excellent electrical and thermal conductivity and ductility, making them suitable for transformer winding processing. However, there are slight differences in purity, performance, and cost.
The 1050 alloy has an aluminum content ≥99.5%, a typical conductivity of approximately 61.0% IACS, and the lowest cost among the two. The 1060 alloy has an aluminum content ≥99.6%, a typical conductivity of 61.0%-61.5% IACS, slightly better in purity and conductivity than 1050, and while slightly more expensive, offers excellent value for money.
Both alloys have impurity levels controlled to extremely low levels, with strict control over impurities such as iron and silicon to avoid affecting conductivity. Both are suitable for O-state (soft state) processing, offering sufficient flexibility for winding requirements and corrosion resistance suitable for transformer operating environments.
If your transformer is for general civilian or industrial auxiliary use, with low efficiency requirements and a focus on extreme cost control, 1050 aluminum is the optimal choice. It meets the conductivity and winding requirements of conventional transformers and offers a significant price advantage, widely used in the ordinary winding of low-to-mid-range dry-type and oil-immersed transformers.
If the transformer is used in applications requiring higher efficiency and stability, such as high-rise buildings, commercial centers, or main transformers in power systems, 1060 alloy is recommended. Its slightly higher purity results in more stable conductivity, effectively reducing no-load and load losses, improving operating efficiency. Simultaneously, its mechanical strength is slightly better than 1050, making it less prone to breakage and deformation during winding, resulting in higher long-term reliability.
It's important to note that neither of these two alloys is suitable for high-corrosion or high-strength applications. For such applications, alloys like 3003 and 5052 thin aluminum strip should be considered, but their conductivity is slightly lower. A comprehensive assessment based on specific requirements is necessary.
Besides thickness, transformer aluminum strip specifications include width, length, tolerances, and surface quality. These seemingly minor details directly impact winding accuracy, insulation performance, and production efficiency. Selection must be based on the transformer's specific design parameters, adhering to three core principles: matching winding dimensions, meeting performance requirements, and adapting to processing technology.
1. Width Selection: Common widths range from 20mm to 1650mm. Custom widths are available based on winding design dimensions. Small transformers typically use 20-100mm widths, while medium and large transformers often use widths of 100mm or more. Some large transformers can be customized with aluminum strips over 1000mm in width.
2. Length Selection: Generally, the length of aluminum strip can be customized according to production needs. The length of a whole roll is usually hundreds to thousands of meters. It needs to be selected reasonably based on the capacity and production efficiency of the winding equipment, while reserving a certain margin to avoid affecting the production schedule due to insufficient length.
3. Tolerances and Surface Quality: Tolerance control is a core detail of aluminum strip specifications. Thickness tolerances must strictly follow industry standards. For example, for aluminum foil with a thickness of 0.08-0.20mm, the tolerance should be controlled within ±8%. For aluminum strips thicker than 0.20mm, the tolerance gradually widens as the thickness increases. If the tolerance is too large, it will lead to uneven winding thickness, affecting insulation performance and conductivity uniformity.
Regarding surface quality, the aluminum strip surface must be smooth, free of scratches, burrs, and oil stains. The edges can be chamfered as needed to prevent burrs from scratching the insulation layer and causing short circuit hazards. This is also one of the core differences between transformer aluminum strips and ordinary aluminum strips.