1350 (EC grade)
99.5 % minimum aluminium with tight limits on impurities that reduce conductivity. Highest conductivity (about 61 – 62 % IACS) but low strength, so it suits flat bar in enclosed switchgear and coiled busbar that is formed and bent.
Electrical conductors
Aluminium Busbar
Aluminium busbar is a solid flat, round or tubular conductor that distributes current inside switchgear, panels, transformers, battery systems and substations. It is made from high-conductivity 1350 or the stronger 6101 alloy. For the same resistance it needs about 1.6 times the cross-section of copper but weighs about half as much and costs much less. Metline supplies extruded and rolled aluminium busbar cut, punched and plated to drawing, to customers worldwide.
- Alloys
- 6101 · 1350 · 6063
- Conductivity
- About 55 – 62 % IACS
- Forms
- Flat, round, tube, coiled
- Standards
- ASTM B317 · IS 5082 · EN 755
Why aluminium busbar?
Copper conducts better, but aluminium conducts more per kilogram and per unit of cost. Pure aluminium has roughly 61 % of the conductivity of annealed copper, and about 30 % of its density. To carry the same current at the same temperature rise, an aluminium bar needs a larger cross-section, yet ends up at roughly half the weight of the copper bar it replaces.
This makes aluminium the usual choice for large busbar systems in switchboards, bus ducts, aluminium smelters, transformer connections, rectifiers, data-centre power distribution and battery energy-storage systems. The larger bar also has more surface area to shed heat. Aluminium busbar is supplied as rectangular flat bar with rounded edges, round bar, tube (bus pipe) for outdoor substations, and in coils for flexible fabrication.
| Property (typical) | Aluminium 1350 | Aluminium 6101-T6 | Copper C11000 |
|---|---|---|---|
| Electrical conductivity | ≈ 61 % IACS | ≈ 55 – 57 % IACS | ≈ 100 % IACS |
| Density | 2.70 g/cm³ | 2.70 g/cm³ | 8.89 g/cm³ |
| Tensile strength | Low (temper dependent) | ≈ 220 MPa | ≈ 220 – 300 MPa |
| Cross-section for equal resistance | ≈ 1.6 × copper | ≈ 1.8 × copper | 1 |
| Weight for equal resistance | ≈ 0.5 × copper | ≈ 0.55 × copper | 1 |
Typical values; actual conductivity depends on temper and is reported on the mill certificate.
1350 or 6101: choosing the alloy
6101-T6 and T6x tempers
An Al-Mg-Si alloy made for electrical use. Strength is several times that of 1350 with conductivity in the mid to high 50s % IACS; tempers such as T61, T63, T64 and T65 trade a little strength for higher conductivity. Preferred for bus pipe, outdoor bus and self-supporting bars.
6063 and 6060
Used where a structural extrusion also carries current, such as rails and enclosures; conductivity is lower than 6101 and should be confirmed per temper.
In India, IS 5082 covers wrought aluminium for electrical purposes, with grade 19501 (equivalent to 1350) and 63401 (equivalent to 6101). ASTM B317 covers extruded 6101 bus conductor, and EN 755 or customer drawings cover European orders.
Sizing aluminium busbar
Busbar is sized by temperature rise, not by a fixed current density. The allowable current depends on the cross-section, the number of bars in parallel and their spacing, orientation (vertical edge-on bars cool better), surface finish (painted or dark surfaces radiate more heat), ambient temperature and enclosure ventilation. IEC 61439 sets temperature-rise limits for switchgear assemblies, and manufacturers verify ratings by test or calculation.
- Start from copper ratings only as a rough guide: an aluminium bar of about 1.6 times the copper cross-section carries similar current
- For AC above a few hundred amperes, skin and proximity effects make thin, wide bars and several bars in parallel more efficient than one thick bar
- Check short-circuit withstand: the bar must survive the fault current for the stated time without overheating or deforming
- Allow for thermal expansion: aluminium expands about 23 µm per metre per °C, so long runs need expansion joints or flexible links
Our electrical resistance calculator estimates resistance and voltage drop for a given size and length.
Standard busbar sizes and weights
| Size (mm) | Cross-section (mm²) | Weight (kg/m) | DC resistance at 20 °C, 1350 (µΩ/m) |
|---|---|---|---|
| 20 × 5 | 100 | 0.27 | ≈ 282 |
| 30 × 5 | 150 | 0.41 | ≈ 188 |
| 40 × 5 | 200 | 0.54 | ≈ 141 |
| 50 × 6 | 300 | 0.81 | ≈ 94 |
| 60 × 10 | 600 | 1.62 | ≈ 47 |
| 80 × 10 | 800 | 2.16 | ≈ 35 |
| 100 × 10 | 1000 | 2.70 | ≈ 28 |
| 120 × 10 | 1200 | 3.24 | ≈ 24 |
| 160 × 10 | 1600 | 4.32 | ≈ 18 |
Resistance calculated from a resistivity of about 0.0282 Ω·mm²/m (61 % IACS). 6101 bars have proportionally higher resistance. Edge radii slightly reduce the true cross-section.
Supply options
- Forms
- Flat bar (rectangular with radiused or full-round edges), round bar, tube, coiled flat
- Lengths
- Standard lengths or cut to size; coiled bar for long continuous runs
- Fabrication
- Cutting, punching, drilling, bending, twisting, flattened and drilled ends
- Surface
- Mill finish, tin plating or silver plating of contact areas, insulating sleeve or powder coating
- Testing
- Conductivity (eddy current, % IACS), dimensions, mechanical tests; EN 10204 3.1 certificate
Making reliable aluminium busbar joints
Most busbar failures start at joints, not in the bar itself. Aluminium forms a thin, hard oxide film within seconds of exposure, and under constant bolt pressure it can slowly creep, which lowers clamping force. Good practice handles both.
Surface preparation
Wire-brush or abrade the contact faces and apply an oxide-inhibiting contact compound immediately; or specify tin or silver plating on contact areas.
Clamping force
Use high-strength steel or stainless bolts with large flat washers and conical spring (Belleville) washers to maintain pressure as the joint heats and cools.
Copper connections
Plate the aluminium (tin) or use copper-aluminium bimetallic transition plates to prevent galvanic corrosion in humid conditions.
Welded joints
For permanent connections, MIG or TIG welding removes contact resistance entirely; use 1xxx or 4xxx filler compatible with conductivity needs.
Overlap length
Make the overlap at least equal to the bar width, and use several bolts across wide bars to spread contact pressure.
Inspection
Check joint resistance with a micro-ohmmeter at commissioning and thermal-image joints under load during maintenance.
Applications
- Switchgear and panels: main and distribution bars in LV and MV boards and motor control centres
- Bus ducts: sandwich and ventilated busway systems for buildings and factories
- Substations: 6101 bus pipe and flat bus for outdoor switchyards
- Industrial electrolysis: high-current bus systems in aluminium smelters, chlor-alkali and electroplating plants
- Batteries and EV: module and pack interconnects, energy-storage containers and charging stations
- Transformers and rectifiers: terminal connections and high-current leads
References and standards
- ASTM B317/B317M – Aluminum-Alloy Extruded Bar, Rod, Tube, Pipe, Structural Profiles, and Profiles for Electrical Purposes (Bus Conductor)
- IS 5082 – Wrought aluminium and aluminium alloy bars, rods, tubes, sections, plates and sheets for electrical purposes
- IEC 61439-1 – Low-voltage switchgear and controlgear assemblies: general rules
- The Aluminum Association – Aluminum Electrical Conductor Handbook
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
Aluminium (aluminum) busbar: frequently asked questions
How much bigger must an aluminium busbar be than copper?
For equal resistance, about 1.6 times the cross-section for 1350 and roughly 1.8 times for 6101-T6. The aluminium bar still weighs only about half as much.
Which is better for busbar, 6101 or 1350?
1350 has the highest conductivity and is easy to bend, but it is soft. 6101 is much stronger with slightly lower conductivity, so it is preferred for self-supporting bars, bus pipe and outdoor installations.
Can aluminium busbar be connected to copper?
Yes, with tin-plated aluminium contact faces or a copper-aluminium bimetallic transition piece, contact compound and spring washers to keep the joint tight and prevent galvanic corrosion.
What current can an aluminium busbar carry?
It depends on the size, arrangement, enclosure and allowed temperature rise. Ratings are established by calculation or test to IEC 61439; use manufacturer tables as a guide, not a fixed amperes-per-square-millimetre figure.
Why do aluminium busbar joints need special care?
Aluminium forms a resistive oxide film and can creep under bolt pressure. Clean or plated contact faces, contact compound and spring washers keep joint resistance low over time.
Do you supply fabricated busbars?
Yes. Busbars can be cut, punched, bent, plated and insulated to your drawing, with conductivity and dimensional reports.
Need aluminium busbar?
Send the alloy, section, length, fabrication drawing and quantity. Our team will quote a delivered price.
