Transformer aluminum is a specialized aluminum alloy used extensively in power transformer manufacturing due to its excellent electrical conductivity, corrosion resistance, and mechanical strength. This aluminum variant is primarily formed into sheets and coils that serve as conductor wires or foils in transformer windings, enabling efficient transmission of electrical energy.
What is Transformer Aluminum?
Transformer aluminum generally refers to high-purity aluminum sheets or foils with stringent composition controls aimed at maximizing electrical conductivity and ensuring stability under transformer operational stresses.
The basic composition revolves around 99.5% to 99.7% pure Aluminum (Al), typically conforming to aluminum grades such as AA1350 or equivalent according to various international standards. Trace elements like iron (Fe) and silicon (Si) are minimized because they degrade electrical conductivity.
Properties and Benefits
| Property | Description |
|---|---|
| Purity | ≥ 99.5% Aluminum for optimum conductivity. |
| Electrical Conductivity | ≥ 61% IACS (International Annealed Copper Standard). |
| Mechanical Strength | Suitable to sustain winding pressure and mechanical stresses during transformer operations. |
| Corrosion Resistance | Natural oxide layer improves long-term durability. |
| Formability | High ductility permits easy drawing into thin foil or sheet. |
These properties allow transformer aluminum to ensure minimal energy losses and enhance transformer efficiency.
Chemical Composition
Typical chemical composition by weight (ASTM B209, AA1350 Type):
| Element | Typical Weight % | Note |
|---|---|---|
| Aluminum (Al) | 99.5 - 99.7% | Principal element |
| Iron (Fe) | ≤ 0.3% | Impurity; lower levels improve conductivity |
| Silicon (Si) | ≤ 0.15% | Impurity |
| Copper (Cu) | ≤ 0.05% | Minimized to prevent conductivity reduction |
| Zinc (Zn) | ≤ 0.05% | Trace element |
| Manganese (Mn) | ≤ 0.05% | Trace element |
| Others | ≤ 0.02% | Combined |
The exact limits may vary slightly depending on national standards or customer requirements.
Alloy Types and Temper
Transformer aluminum sheet most commonly comes in alloy AA1350 with various tempers to balance mechanical properties and electrical conductivity:
| Temper | Designation | Typical Features |
|---|---|---|
| O (Annealed) | Fully soft | Maximum electrical conductivity but lowest mechanical strength. Used in transformer foils. |
| H14 | Strain hardened | Improved strength at slight cost to conductivity. Used in various winding applications. |
| H19 | More strain hardened | Higher mechanical strength; reduced ductility. |
Annealed (O temper) sheet exhibits the highest electrical conductivity needed for low power loss transformer windings. Harder tempers may be used for mechanical reinforcement layers or special electromechanical transformer components.
Standards and Implementation
Transformer aluminum products typically comply with the following implementation standards:
| Standard | Region | Coverage |
|---|---|---|
| ASTM B209 | USA | Aluminum and Aluminum-Alloy Sheet and Plate |
| EN 573-3 | Europe | Chemical composition of wrought aluminum |
| GB/T 3190 | China | Chemical composition of aluminum weld wire and rods |
| IS 737 (Part 8) | India | Wrought aluminum foil and sheet for transformer windings |
Compliance is critical to ensure the exact purity, physical properties, and dimensional tolerances needed for transformer manufacturing.
Physical Dimensions and Mechanical Parameters
Transformer aluminum sheets and foils are supplied in varied thicknesses depending on the transformer winding requirements:
| Parameter | Values / Range |
|---|---|
| Sheet thickness | 0.2 mm to 3.0 mm |
| Foil thickness | 0.015 mm to 0.1 mm |
| Width | Usually up to 1500 mm or cut-to-size |
| Electrical resistivity | ≤ 0.0282 μΩ·m (for O temp) |
| Tensile strength | 40 - 80 MPa (according to temper) |
| Elongation | > 10% (O temper indicative) |
Proper manufacturing and tempering play crucial roles in achieving these parameters without compromising electrical performance.
Applications in Transformer Manufacturing
- Transformer Windings: Because of high conductivity and manageable strength, transformer aluminum is directly used for winding foils, sheets, and conductors. This systematically reduces eddy current loss.
- Signal Transformers: Thin foil forms used in finely-stranded windings to improve efficiency.
- Distribution transformers: Stable, high-purity aluminum sheets reduce overall transformer size and operating temperature.
- Custom Accessories: Winding support fins and cooling parts with same electrical properties.
Transformer aluminum's prioritization on conductivity and purity has widespread adoption where specific standards like IEC or ANSI need precision materials.
Quality Control & Testing
Stringent quality control must confirm:
- Certified chemical composition via spectrometry.
- Electrical conductivity tests following ASTM or IEC guidelines.
- Mechanical testing (tensile, elongation).
- Dimensional accuracy (thickness and flatness).
- Surface inspection to avoid foreign inclusions and defects.
Any batch failing to meet criteria is segregated due to the critical nature of transformer performance pieces.
