What a Conductive Aluminum Busbar Does
A closed bus duct, also called busbar trunking, is an engineered assembly that carries current through rigid metal conductors instead of cables. The typical construction combines a metal enclosure in steel or aluminium, one or more conductive bars, insulating supports and separators, and connection accessories. The enclosure protects the conductors mechanically and provides the earth path, while the conductive bars carry the load current.
Aluminium plate is the preferred conductor material for these assemblies because it combines high electrical conductivity with low density and good corrosion resistance. The two commercial purity grades used for bus duct work are 1060 and 1070 aluminium plate, both of which keep impurities low enough to hold conductivity close to the theoretical value for aluminium while remaining easy to bend, punch and weld.
Material Data for 1060 and 1070 Busbar
| Property | 1060 aluminium | 1070 aluminium |
|---|---|---|
| Aluminium content | 99.60 percent minimum | 99.70 percent minimum |
| Electrical conductivity | 60 percent IACS or above, typically about 61 percent | Typically about 62 percent IACS |
| Thermal conductivity | About 230 W/(m.K) | About 235 W/(m.K) |
| Density | About 2.71 g/cm3 | About 2.70 g/cm3 |
| Corrosion resistance | Good; oxide film re-forms after damage | Very good; slight advantage from higher purity |
| Weldability | Gas welding, hydrogen atom welding and contact welding are all used; brazing is difficult | Similar to 1060 |
Because content of iron, silicon, copper and other impurities is tightly limited, resistivity stays low and stable. Copper in particular has to be kept below the specification limits, since even small additions reduce conductivity and attack corrosion resistance. Composition for both grades is specified under GB/T 3190 and EN 573-3, sheet and plate product requirements follow ASTM B209 and GB/T 3880, and mechanical values are taken from EN 485-2.
Advantages in Bus Duct Design
High conductivity: conductivity of 60 percent IACS and above keeps resistance low, so resistive losses along the bus duct run are minimised and temperature rise at rated current stays within assembly limits.
Low weight: aluminium is roughly one third the density of copper, so a bus duct of equal current rating is significantly lighter, which reduces structural support, handling and installation effort.
Corrosion resistance: after suitable surface treatment, the conductor resists humid and mildly aggressive atmospheres, so service life in plant rooms, tunnels and outdoor enclosures is extended.
Machinability: the plate shears, punches, bends and drills cleanly, which keeps fabrication of bars and enclosure panels straightforward and repeatable.
Joining: gas welding, hydrogen atom welding and contact welding are all practical; mechanical joints are made with plated contact surfaces and controlled torque.
Thermal performance: high thermal conductivity helps spread local heating at joints and terminations, reducing hot spot risk.
Specifications and Tempers
| Alloy | Tempers | Thickness (mm) | Width (mm) | Length (mm) |
|---|---|---|---|---|
| 1060 aluminium plate | F, O, H111, H112 | 10 to 400 | 100 to 2500 | 400 to 15000 |
| 1070 aluminium plate | F, O, H111, H112 | 10 to 400 | 100 to 2500 | 400 to 15000 |
Common bar cross sections for conductive busbar are 80 x 10 mm and 70 x 3 mm, with other sections produced to drawing. Soft O temper is used where the bar must be bent to follow a route or where a flexible connection is required, while H111 and H112 are chosen for straight rigid runs that need higher stiffness. Assembly testing of finished busbar trunking systems is governed by IEC 61439-6, so conductor dimensions, joint design and enclosure construction are normally validated together as a complete assembly rather than as separate parts.
Applications and Fabrication Notes
Bus duct conductors and enclosures: the conductive bar is the current carrying element, and the same plate is used for the protective shell, which must combine mechanical strength with good thermal behaviour.
Battery soft connectors: thin O temper sheet is used for flexible links between cells and modules where vibration has to be absorbed.
Charging piles: busbars distribute power inside DC fast charging cabinets, where low weight and short bends simplify layout.
Heat sinks and radiators: plate and profile stock is used for thermal management hardware in power electronics.
Transformer and switchgear links: positive and negative horizontal bars and upper negative bars connect equipment inside enclosures.
Three fabrication points dominate quality. Contact surfaces must be flat and clean, because joint resistance is set by surface condition rather than by bulk resistivity. Bolt torque must be controlled so that creep in the soft temper does not relax the joint over time. Finally, dissimilar metal interfaces must be plated or separated to prevent galvanic corrosion where aluminium meets copper or steel hardware.
Frequently Asked Questions
Q: What is the difference between 1060 and 1070 aluminium busbar?
1070 has the higher guaranteed aluminium content, 99.70 percent against 99.60 percent for 1060, which gives it slightly higher conductivity and marginally better corrosion resistance. Both are used for bus duct conductors, and the choice usually comes down to the conductivity target and availability.
Q: What conductivity can be expected from 1060 busbar plate?
1060 plate is normally supplied with conductivity of 60 percent IACS or above, typically around 61 percent IACS. That value is what keeps losses and temperature rise low in a bus duct running at rated current.
Q: Why is aluminium used instead of copper for bus ducts?
Aluminium conducts about 61 percent as well as copper by volume but weighs roughly a third as much, so a duct of equivalent rating is far lighter. Lower weight reduces support structure, handling and installation cost, and in many installations no additional space is needed.
Q: Which tempers are supplied for conductive aluminium plate?
F, O, H111 and H112 are the usual supply conditions. O temper is the softest and is used where bending or flexibility is required, while H111 and H112 provide higher stiffness for straight rigid conductor runs.
Q: Why is brazing difficult on 1060 and 1070 plate?
The tenacious aluminium oxide film must be displaced before any filler metal can wet the surface, which makes brazing unreliable at production scale. Gas welding, hydrogen atom welding and contact welding avoid that problem and are therefore the preferred joining methods.
Q: How is a busbar joint made reliable over long service?
The contact faces are machined or brushed flat and clean, plated where dissimilar metals meet, and bolted to a controlled torque with suitable washers. Avoiding over torque is important in soft tempers because excessive stress causes creep and gradual loss of clamping load.
