High-Current Flexible Busbar | 400A to 4000A Custom Designs

Carsai manufactures custom high-current flexible busbar products for transformers, busducts, switchgear, battery systems, inverters, rectifiers and industrial power-distribution equipment.

Our flexible busbars can be manufactured from multilayer copper foil, copper braid or aluminum conductors according to the required current, available installation space and mechanical movement. Common project requirements range from a compact 400 amp flexible busbar to flexible connections designed for 2000A, 2500A, 3200A or 4000A power systems.

Each product is manufactured according to the customer’s drawing rather than selected only from a standard current rating. We can customize the conductor cross-section, foil thickness, number of layers, flexible length, terminal dimensions, hole pattern, bends, plating and insulation.

To receive an accurate quotation, send us the continuous current, peak current, allowable temperature rise, conductor dimensions, terminal design, cooling conditions and required quantity.

For an overview of all available flexible conductor structures, visit our Flexible Busbar Manufacturer page.

What Is a High-Current Flexible Busbar?

A high-current flexible busbar is an electrical conductor designed to carry several hundred or several thousand amperes while accommodating limited movement between connected components.

Unlike one thick, rigid copper bar, a flexible design may use:

• Multiple thin copper sheets
• Stacked copper foils
• Braided copper conductors
• Multilayer aluminum strips
• Flexible conductors with rigid terminal plates

The terminal areas are normally compressed, welded, brazed or formed into solid mounting sections. The central conductor remains flexible enough to absorb vibration, thermal expansion and minor alignment differences.

High-current flexible busbars are commonly installed where rigid busbars connect to equipment that may move, vibrate or expand during operation.

Typical examples include:

• Transformer terminals
• Busduct and busway interfaces
• Switchgear and circuit breakers
• Battery racks and energy storage systems
• Inverters and PCS equipment
• Rectifiers and industrial power supplies
• Generators
• Welding equipment
• High-current DC distribution systems

The purpose of the flexible section is not only to simplify installation. It can also reduce mechanical stress on terminal palms, bushings, insulators, battery terminals and other sensitive components.

Flexible Busbar Current Ratings

Customers often search for flexible busbars using a specific current rating. Common requirements include:

These current values are useful for defining the general project range, but they are not enough to determine the final busbar dimensions.

A 2000A busbar installed in an open and ventilated area may require a different conductor cross-section from a 2000A busbar installed inside a compact enclosed cabinet.

The final design must consider both electrical and thermal conditions.

What Determines Flexible Busbar Current Capacity?

The current capacity of a flexible busbar depends on several related factors.

Conductor material

Copper provides high conductivity and allows a relatively compact conductor cross-section. It is therefore commonly selected for high-current systems where installation space is limited.

Aluminum is lighter and may reduce material cost, but it normally requires a larger cross-sectional area to carry the same current with a similar temperature rise.

Common copper material options include:

• C11000 copper
• Cu-ETP copper
• T2 copper
• Oxygen-free copper for special applications

The aluminum grade should be selected according to conductivity, forming performance, terminal design and welding requirements.

Total conductor cross-section

The total cross-section is determined by conductor width, individual layer thickness and number of layers.

For example, a multilayer copper busbar may be constructed from:

• Ten layers of 0.5 mm copper
• Twenty layers of 0.3 mm copper
• Another customized foil combination

Using more thin layers generally improves flexibility. Using fewer thick layers produces a stiffer connection.

Two conductors with the same total cross-section may therefore have different bending characteristics.

Ambient temperature

A busbar operating in a hot transformer room or enclosed switchgear cabinet has less ability to release heat than one installed in a cooler, open environment.

The expected ambient temperature should be provided before conductor sizing is finalized.

Cooling and ventilation

Natural air circulation, forced ventilation and conductor orientation all affect heat dissipation.

A horizontal busbar, vertical busbar and tightly enclosed busbar may operate at different temperatures even when their material and cross-section are identical.

Allowable temperature rise

Different equipment manufacturers may specify different maximum conductor or terminal temperatures.

The permitted temperature rise should therefore be confirmed together with the expected ambient temperature.

Duty cycle

Some applications carry continuous current, while others operate intermittently.

A flexible busbar used in continuous power distribution requires a different thermal evaluation from one carrying short-duration welding current or occasional peak loads.

Terminal contact resistance

The conductor itself may have sufficient cross-section, but excessive resistance at the bolted joints can still cause overheating.

Terminal performance depends on:

• Contact surface area
• Surface flatness
• Plating
• Bolt size and quantity
• Fastening torque
• Joint preparation
• Mating-terminal material

The terminal areas must be designed together with the flexible conductor.

Multilayer Copper Busbars for High Current

Multilayer copper foil busbars provide a compact, flat connection for high-current systems.

The central section contains several thin copper layers. The ends are consolidated into solid terminals with mounting holes.

This construction offers:

• High electrical conductivity
• Large terminal contact surfaces
• Controlled bending direction
• Compact installation
• Customizable conductor cross-section
• Precise terminal geometry
• Good compatibility with rigid copper busbars

A multilayer structure is often suitable for a flexible busbar 1000a, 1250A, 2000A or higher when the available space favors a flat conductor.

The conductor width, layer quantity and flexible length must be selected together. Increasing only the number of layers may raise current capacity but can also increase stiffness.

Braided Copper Busbars for High-Current Connections

Braided copper busbars are made from woven copper wires and provide greater softness than many multilayer foil designs.

They are commonly selected where the connection must absorb:

• Continuous vibration
• Movement in several directions
• Frequent thermal cycling
• Larger alignment variation
• Mechanical shock

A braided high-current connector can be supplied with pressed, welded or attached copper terminal plates.

Bare copper and tinned copper braid are both available according to the environmental and connection requirements.

Braided designs can be used for transformers, generators, welding machines, switchgear and high-current grounding connections. However, their cross-section, braid density and terminal construction must be suitable for the required electrical load.

High-Current Flexible Links for Transformers and Busducts

Transformer and busduct systems commonly use flexible links in the 1600A to 4000A range.

A flexible link 3200a may connect:

• A transformer to a busduct
• A transformer to switchgear
• Two rigid busbar sections
• Busway to a circuit breaker
• Busduct to a generator
• Switchboard busbars to external equipment

These connections may need different terminal designs at each end.

One side may match a four-hole transformer terminal palm, while the other side may connect to a busduct conductor with a different width and hole pattern.

Custom options include:

• Straight links
• 90-degree terminal arrangements
• Z-shaped offsets
• Different terminal widths
• Single- or multi-hole ends
• Slotted mounting holes
• Tinned contact surfaces
• Insulated flexible sections
• Copper-to-aluminum transition terminals

400A to 800A Flexible Busbars

Lower-current products in this category are commonly used inside battery cabinets, inverters, switchboards and compact power equipment.

A flexible busbar 400a or 400a flexible busbar may use a relatively compact multilayer copper conductor. However, its final size still depends on temperature, insulation and installation space.

Similarly, a flexible busbar 500a, 500a flexible busbar, flexible busbar 600a or 630a flexible busbar should not be selected only from a generic current chart.

At these current levels, a small change in conductor length, enclosure ventilation or terminal size can noticeably affect operating temperature.

An 800a flexible busbar may be manufactured using stacked copper layers, braid or another flexible construction depending on the required movement.

1000A to 2000A Flexible Busbars

Flexible busbars in the 1000A to 2000A range are frequently used for transformers, busducts, large inverters, rectifiers and energy storage systems.

A flexible busbar 1250a may connect a transformer to a low-voltage switchboard or bridge two sections of rigid busbar.

A flexible busbar 2000a normally requires careful attention to:

• Copper cross-section
• Terminal width
• Number of mounting bolts
• Heat dissipation
• Flexible-section length
• Short-circuit forces
• Surface plating

A 2000a flexible busbar with an undersized terminal pad may overheat at the joint even if the central conductor has enough copper.

The mating busbar and fastening system must therefore be included in the design review.

2500A to 4000A Flexible Busbars

High-current systems above 2500A usually require large conductor sections and substantial terminal contact areas.

A flexible busbar 2500a or 2500a flexible busbar may use multiple parallel flexible conductors when one very wide busbar is impractical.

For 3150A and 3200A systems, installation space, phase spacing and cooling become increasingly important. A request for a flexible busbar 3,150 a or flexible busbar 3200a should include the equipment layout and terminal dimensions.

A flexible busbar 4000a may be designed as:

• One wide multilayer conductor
• Several parallel flexible links
• Multiple braided connectors
• A phase assembly with separate conductors
• A flexible section connected to rigid copper bars

A 4000a flexible busbar cannot be standardized without knowing the allowable temperature rise and installation conditions. The same applies when a drawing identifies the component as a flexible busbar 4,000 a.

Large-current products must also be evaluated for mechanical forces during short-circuit events. Supports, terminal bolts and connected rigid busbars must withstand the complete system load.

Terminal Design and Surface Treatment

Carsai can manufacture high-current flexible busbars with customized terminals, including:

• One-hole terminals
• Two-hole terminals
• Four-hole terminal palms
• Multiple-hole connection plates
• Different terminal shapes at each end
• Bent and offset terminals
• Wider terminal pads
• Copper end plates attached to braid
• Copper-to-aluminum transition ends

Available surface treatments may include:

• Bare copper
• Tin plating
• Nickel plating
• Silver plating
• Selected terminal-area plating

Tin plating is widely used for industrial busbar terminals because it provides a stable contact surface and improved corrosion protection.

The plating thickness and coverage area should be shown on the drawing.

Insulation Options

High-current flexible busbars may be supplied bare or insulated.

Available insulation options include:

• Heat-shrink tubing
• PVC sleeves
• Epoxy coating
• Powder coating
• Plastic protective covers
• Partial insulation

The mounting surfaces normally remain exposed.

Insulation selection should consider operating voltage, conductor temperature, required flexibility, creepage distance, phase spacing and flame-resistance requirements.

Information Required for a Quotation

To quote a 400A to 4000A flexible busbar, please provide:

• 2D or 3D drawing
• Continuous current
• Peak and short-circuit current
• Ambient temperature
• Allowable temperature rise
• Cooling or ventilation conditions
• Copper or aluminum grade
• Conductor width and thickness
• Individual foil thickness
• Number of layers
• Flexible-section length
• Terminal dimensions
• Hole diameter and spacing
• Plating requirement
• Insulation requirement
• Order quantity
• Annual demand

When a complete drawing is unavailable, we can initially review a sketch, terminal layout, existing sample or installation photo.

Frequently Asked Questions

Can you determine busbar size from the current alone?

No. Current is only one design input. Ambient temperature, cooling, installation space, conductor length and allowable temperature rise must also be considered.

Can you manufacture flexible busbars above 4000A?

Large-current designs can be evaluated according to the drawing and operating conditions. Multiple parallel conductors may be used when one conductor is not practical.

Are copper braid and multilayer copper foil rated in the same way?

No. They may have similar total copper cross-sections but different cooling, flexibility and terminal construction. Each design must be reviewed separately.

Can high-current flexible busbars be insulated?

Yes. Heat-shrink, PVC, epoxy, powder coating and other insulation options can be applied while leaving terminal contact areas exposed.

Can both terminal ends have different dimensions?

Yes. Each end can have a different width, thickness, bend, offset and hole pattern.

Can you manufacture prototypes before batch production?

Yes. Prototype and small-batch production can be evaluated before regular production.

Request a High-Current Flexible Busbar Quotation

Carsai manufactures custom flexible busbars for 400A, 500A, 630A, 800A, 1000A, 1250A, 2000A, 2500A, 3200A and 4000A electrical systems.

Send your continuous current, allowable temperature rise, conductor dimensions, terminal drawing, plating, insulation, cooling conditions and required quantity.