Epoxy powder coating
Applied by electrostatic spray or fluidised bed and cured. Hard, adherent and conformal over bends, with high dielectric strength. Sharp edges coat thinner, so edge radii must be specified.
Electrical conductors
Insulated High-Voltage Aluminium Busbars
An insulated high-voltage aluminium busbar is a rigid aluminium conductor, formed to shape and covered with an insulating layer except at its contact faces. It carries high current in EV battery packs, inverters, energy storage and switchgear at about half the weight of copper for the same resistance. Metline supplies conductor bar and formed, insulated busbars to drawing, with certified material, worldwide.
- Conductor
- 1350, 1060, 6101
- Conductivity
- about 55 – 62 % IACS
- Insulation
- Epoxy, PA, heat-shrink, film
- Weight vs copper
- about 50 % at equal resistance
What is an insulated high-voltage aluminium busbar?
A busbar is a solid conductor that distributes current between components. In compact high-voltage systems, such as an electric vehicle pack running at 400 or 800 V, bare bars would need large air gaps to prevent flashover. Insulating the bar lets designers route conductors closely and safely, protects against accidental contact and keeps debris from bridging phases.
An insulated busbar is a system with three parts that must be specified together: the conductor (alloy, temper, cross-section and shape), the insulation (material, thickness, temperature class and dielectric rating), and the connections (exposed contact faces, plating, holes, welds or fasteners). A bar that fits the space is not yet a busbar; it also needs a thermal and electrical review for the current, voltage and environment it will see.
Aluminium is increasingly chosen for these parts because weight and cost matter in vehicles and large installations. For the same DC resistance an aluminium bar needs about 1.6 times the cross-section of copper, yet weighs only about half as much, and it costs considerably less per ampere carried. The penalty is a larger section and more careful joint design, because aluminium forms a hard oxide and creeps under sustained bolt load.
Conductor alloys and their electrical properties
The choice is a trade-off between conductivity and strength. Pure grades conduct best; 6101 adds strength for bars that must stay rigid over long spans or carry mechanical load. Values are typical; guaranteed minimum conductivity is set by the order standard and reported on the certificate.
| Alloy / temper | Electrical conductivity (% IACS) | Resistivity at 20 °C (µΩ·cm) | Typical tensile strength | Notes |
|---|---|---|---|---|
| 1350 (EC grade) | about 61 – 62 | about 2.8 | about 80 – 190 MPa depending on temper | Electrical conductor grade, Al ≥ 99.50 % |
| 1060 | about 61 – 62 | about 2.8 | about 70 – 130 MPa depending on temper | Widely used for formed EV busbars |
| 1050A | about 60 – 61 | about 2.85 | about 65 – 150 MPa depending on temper | European equivalent, good formability |
| 6101-T6 / T61 / T63 | about 55 – 57 | about 3.0 – 3.1 | 200 – 220 MPa (T6) | Higher strength for rigid or long bars |
| Copper C11000 (reference) | 100 | 1.72 | 220 – 300 MPa | Smaller section, about 3.3 × the density |
| Comparison at equal resistance | Aluminium (1350 / 1060) | Copper |
|---|---|---|
| Relative cross-section | about 1.6 | 1.0 |
| Relative weight | about 0.5 | 1.0 |
| Density | 2.70 g/cm³ | 8.89 g/cm³ |
| Thermal expansion | about 23 µm/m·°C | about 17 µm/m·°C |
Insulation options and how to choose
Polyamide (PA11 / PA12) coating
Thermoplastic coating applied by fluidised bed. Tough and flexible, resists cracking under vibration and thermal cycling, and tolerates later bending better than epoxy.
Heat-shrink tubing
Polyolefin or other sleeves shrunk over straight and gently bent bars. Low tooling cost and easy to change; less suited to complex 3D shapes and tight bends.
Laminated film
PET, PI or similar films laminated around flat conductors, often in stacked laminated busbars that cut inductance in inverters.
Over-moulded or extruded sleeves
Silicone, TPE or other polymers moulded or extruded onto the bar. Thick, robust insulation for high voltage and harsh environments.
Partial coverage
Insulation only where clearance is tight, with bare sections elsewhere. Saves cost but needs careful creepage and clearance design.
Select insulation on four properties: dielectric withstand at the system voltage with margin, continuous temperature class above the bar's hot-spot temperature, flame rating (often UL 94 V-0 for battery packs), and mechanical durability against vibration, abrasion and thermal cycling. Ask for the tracking index (CTI) where the bar sits in a humid or contaminated environment.
Design checks for a high-voltage busbar
| Design check | What to confirm | Reference |
|---|---|---|
| Current rating | Temperature rise of the bar at continuous and peak current, including joints | IEC 61439-1 temperature-rise limits; thermal simulation or test |
| Short-circuit withstand | Mechanical force and thermal rise during fault current | System fault study |
| Creepage and clearance | Distances at exposed terminals and where insulation ends | IEC 60664-1; ISO 6469-3 for vehicles |
| Dielectric withstand | AC or DC withstand voltage of the insulation, and insulation resistance | Product or customer specification |
| Partial discharge | Inception voltage for 800 V-class and higher systems | Customer specification |
| Thermal cycling and vibration | Insulation adhesion and joint stability over life | Vehicle or application test plan |
Aluminium needs particular attention at joints. Clean and abrade the contact surface, use a contact compound or plating, and keep bolt preload steady with spring or Belleville washers so creep does not loosen the joint. Contact faces are often tin- or nickel-plated, or a copper–aluminium bimetallic insert is used where the bar meets a copper terminal. In battery packs, aluminium busbars are frequently laser or ultrasonically welded to cell tabs instead of bolted.
From conductor bar to insulated part
- Conductor stockExtruded or rolled flat bar, or strip slit from coil, in the specified alloy and temper with conductivity certified.
- Cut and pierceBlanks are cut, punched or CNC machined for holes and slots, and deburred.
- FormBars are bent on CNC benders to the 3D routing; edge radii are kept generous so insulation covers evenly.
- Prepare surfacesContact faces are masked or plated; the rest of the bar is cleaned and pretreated for coating adhesion.
- InsulatePowder coating, fluidised-bed PA, heat-shrink, lamination or over-moulding, then curing.
- TestCoating thickness, adhesion, dielectric withstand and insulation resistance on each part or batch, with dimensional checks against the drawing.
Supply range and documentation
Supply range
- Conductor forms
- Flat bar, strip, formed 3D bars, flexible laminated straps
- Section
- Thickness and width to your current rating; typical EV bars are a few mm thick and tens of mm wide
- Alloys
- 1350, 1060, 1050A, 6101; other conductor grades on request
- Insulation
- Epoxy powder, PA11/PA12, heat-shrink, laminated film, over-moulded polymers
- Contact finish
- Bare, tin-plated, nickel-plated, or with bimetallic copper–aluminium insert
- Documents
- Material certificate with conductivity, dimensional report, coating and dielectric test records
For straight conductor bar without insulation, see our aluminium busbar page.
How to order insulated aluminium busbars
- Specify3D model or drawing with conductor section and routing, alloy and temper, minimum conductivity, exposed contact areas and their finish, insulation type and thickness, system voltage, test voltage, temperature class, flame rating and quantity.
- QuoteWe confirm alloy, temper, tolerances, certification, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessPrototypes are made and tested for fit, dielectric strength and insulation adhesion; after approval, production parts are formed, insulated and tested.
- DocumentEach delivery includes the conductor material certificate (EN 10204 3.1) with conductivity, plus dimensional and dielectric test records.
- ShipParts are packed in partitioned cartons or trays to protect the insulation and shipped by sea or air on EXW, FOB, CIF or DAP terms.
References and standards
- IEC 61439-1 – Low-voltage switchgear and controlgear assemblies: general rules (temperature rise)
- IEC 60664-1 – Insulation coordination for equipment within low-voltage supply systems
- ISO 6469-3 – Electrically propelled road vehicles: safety specifications, electrical safety
- ASTM B317 / B317M – Aluminum-Alloy Extruded Bar, Rod, Pipe and Structural Shapes for Electrical Purposes (Bus Conductor)
- UL 94 – Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances
Insulated aluminium (aluminum) busbars: FAQ
Why use aluminium instead of copper for EV busbars?
Weight and cost. For the same resistance an aluminium bar needs about 1.6 times the cross-section of copper but weighs about half as much and costs less. Where space allows the larger section, aluminium reduces pack mass and material cost.
Which aluminium alloy is best for busbars?
1350 or 1060 for maximum conductivity (about 61 – 62 % IACS) and easy forming. 6101 in T6 or T61 is used where the bar must be stiffer or stronger, accepting conductivity of about 55 – 57 % IACS.
Is epoxy or PA coating better for busbar insulation?
Epoxy powder gives high dielectric strength and a hard finish and is the common choice for rigid bars. Polyamide (PA11/PA12) is tougher and more flexible, so it resists cracking from vibration, thermal cycling or later bending. The right choice depends on voltage, temperature and mechanical duty.
How are aluminium busbars connected to copper terminals?
With plated contact faces (tin or nickel), a contact compound, and bolted joints that use spring washers to hold preload. For permanent joints, bimetallic copper–aluminium inserts or friction-welded transitions avoid galvanic corrosion at the interface.
What tests are done on insulated busbars?
Typically dimensional inspection, insulation thickness, adhesion, dielectric withstand (hipot) and insulation resistance, with partial discharge testing for 800 V-class systems where specified. Conductor conductivity is reported on the material certificate.
Can Metline supply both conductor bar and finished insulated busbars?
Yes. We supply certified conductor bar and strip, and formed and insulated busbars made to your drawing, to customers worldwide.
Need insulated aluminium busbars?
Send the drawing, voltage, current and insulation requirement. We will reply with conductor, insulation and test options and a delivered price.
