Braided Forissier Braided Copper Strip Selection Guide

Braided Forissier Braided Copper Strip Selection Guide

In high current power equipment, hard busbar connections often experience mechanical stress due to thermal expansion, contraction, vibration, or installation tolerances, leading to poor contact and even equipment damage. Braided flexible connections are the key components to solve this problem. Forissier Company (TRESSE METALLIQUE J. FORISSIER), as a brand under the International Wire Group, offers copper braided tapes with standardized cross-sections ranging from 60mm ² to 2000mm ², which are widely used in medium voltage switchgear, circuit breakers, transformers, industrial furnaces, and electrolytic cells.

This article is aimed at electrical design engineers and on-site maintenance personnel, systematically introducing the technical characteristics, selection criteria, parallel use rules, terminal processing requirements, and installation precautions of Forissier braided connectors, helping you make the optimal choice under different environmental temperatures and current carrying requirements.

Product Structure and Technical Advantages

1.1 Weaving tape material and process

Forissier's flexible connectors use flat or circular braided copper strips, with copper wire diameters of 0.10 mm (fine wire) or 0.20 mm (standard wire) available, and can provide 0.30 mm as needed. Fine wire braiding provides better flexibility and is suitable for high vibration or frequent displacement situations; Standard silk provides higher mechanical strength.

Copper wire material: Cu ETP (electrolytic tough copper) that complies with NF EN 13602 (formerly NFC 31 111) standard, with a copper content of ≥ 99.9%, a 20 ° C resistivity of ≤ 0.017241 Ω· mm ²/m (100% IACS), and a mechanical strength of ≥ 200 MPa in annealed state.

Connection terminal: formed by crimping or brazing bare copper tubes, with a wall thickness of 2 mm and standard lengths of 50, 80, 100, and 120 mm. The terminal surface can be tin plated (5 μ m conventional, 15 μ m harsh environment), silver plated (5/10 μ m), nickel plated, or gold plated.

Brazing process: Dip brazing can be used between copper pipes and braided tapes to effectively reduce contact resistance, prevent capillary water absorption, prevent external corrosion from spreading to the inside of the connection, and significantly extend the service life.

1.2 Main advantages

TMF solution: Customize weaving types and terminal angles (such as angled terminals) according to customer needs for easy installation.

Low contact resistance: The brazing process reduces heat generation and improves current carrying capacity.

Anti electric force damage: The copper tube is flaring treated on the braided belt side to prevent the copper wire from being cut or worn under the action of electric force.

Long lifespan: Both mechanical and electrical characteristics are guaranteed, reducing maintenance frequency.

Current carrying capacity and selection table

2.1 Rated current conditions

The data table provided by Forissier provides the maximum continuous current (I Max) allowed for a single connector at stable ambient temperatures (25 ° C, 35 ° C, 45 ° C). The limiting condition is the final temperature of the conductor:

Bare copper or red copper connector: ≤ 85 ° C

Tin plated copper connector: ≤ 105 ° C

The values in the table are based on the following assumptions:

Only a single connector works, without adjacent heat sources;

Stable ambient temperature;

Vertical installation of connectors (recommended).

2.2 Comparison of standard cross-section and current carrying capacity

The following are the current carrying capacities of some typical sections (unit: A), organized according to the original table:

Sectional area (mm ²) Terminal width (mm) Bare copper/red copper - Environment 25 ° C Bare copper -35 ° C Bare copper -45 ° C Tin plating -25 ° C Tin plating -35 ° C Tin plating -45 ° C

60 30/40 351 317 280 389 359 326

75 30/40 389 351 317 426 393 358

100 40/50 426 393 358 440 405 369

120 (2×60) 40/50 440 405 369 480 442 403

150 40/50 480 442 403 505 456 403

200 40/50 505 456 403 560 516 470

250 50/60 560 516 470 602 554 505

300 (2×150) 50/60 542 490 433 619 571 539

400 (2×200) 60/80 619 571 539 663 611 556

500 (2×250) 60/100 663 611 556 701 646 588

600 (3×200) 60/80 747 689 627 826 761 693

800 (4×200) 80/100 826 761 693 991 913 832

1000 (4×250) 80/100 991 913 832 1153 1063 967

1200 (6×200) 100/120 1153 1063 967 1356 1250 1137

1600 (8×200) 120/160 1356 1250 1137 1468 1353 1232

2000 (8×250) 160/200 1468 1353 1232 1775 1636 1490

Selection example:

The ambient temperature is 35 ° C, and a current carrying capacity of 600 A is required. Bare copper connectors are selected: according to the table, 150 mm ² (505A) is insufficient, and 200 mm ² (560A) is still insufficient. 250 mm ² (602A) or 300 mm ² (619A) are needed. Alternatively, tin plating of 200 mm ² (560A is still insufficient) can be used, and ultimately tin plating of 250 mm ² (619A) or two 150 mm ² parallel wires can be chosen.

Note: The values in the above table are for a single connector, and when multiple connectors are connected in parallel, they need to be multiplied by the parallel factor.

2.3 Derating factor for parallel use

When multiple braided connectors are used in parallel for the same phase, the total current carrying capacity is not simply superimposed due to uneven current distribution. The following parallel coefficient correction is required:

Quantity coefficient of parallel connectors

1 1.0

2 1.83

3 2.54

4 3.25

5 3.96

6 4.48

7 5.5

8 6.5

Calculation method:

Determine the number of connectors n that need to be connected in parallel.

The current carrying capacity of a single connector is I2 single (refer to the table based on the cross-section and ambient temperature).

The actual total current carrying capacity of this combination is equal to I2 single multiplied by the parallel coefficient.

To achieve the target current Itotal, the required single current carrying capacity is I2 single ≥ Itotal/coefficient, and then the cross-section is reverse checked.

Case: The environment is 35 ° C and requires a total current of 1500 A. It is planned to use 4 parallel connections. If the coefficient of 4 is 3.25, then each one needs to provide 1500/3.25 ≈ 462 A. According to the table, bare copper at 35 ° C: 250 mm ² is 516 A, which meets the requirements. Therefore, four 250 mm ² bare copper braided tapes are selected in parallel.

Guidelines for Terminal Drilling Specifications and Selection

3.1 Standard drilling types

Forissier offers three standard drilling types (Type I, II, III) to accommodate different device wiring terminals:

Type I: Single hole centered, suitable for small and medium-sized sections (60-75 mm ²), with A × B sizes of 30 × 30 or 40 × 40 mm.

Type II: Double hole, suitable for 100-400 mm ², specific dimensions are shown in the table below.

Type III: Four hole, suitable for large cross-sections (400~2000 mm ²).

3.2 Recommended terminal dimensions and drilling layout for each section

Sectional area (mm ²) Terminal length A (mm) Width B (mm) Hole spacing C (mm) Hole edge distance D (mm) Recommended drilling type

60-75 30 or 40-- I

100 - 120 80 40 40 - II

150 - 200 80 - 100 50 40 - II

250 - 300 100 60 50 40 II/III

400 - 800 100 - 120 60 - 80 40 - 50 40 - 50 III

1000 - 1200 120 - 160 60 - 100 60 50 III

1600 - 2000 160 - 200 60 - 70 60 - 70 60 III

Key dimension description:

A: Terminal length (along the direction of the braided tape)

B: Terminal width (perpendicular to the braided tape)

C: Center distance between two holes (Type II/III)

D: The distance from the center of the outermost hole to the edge of the terminal

Hole diameter ∅: standard 10-18mm, can be customized according to needs

Selection suggestion:

For medium voltage circuit breakers or switchgear, type II or III drilling is usually selected to match the equipment terminal block.

If the device terminal is a screw structure, flat terminals without drilling holes can be used (crimping or welding should be provided).

3.3 Special Processing

Angle forming: It can produce terminals with angles (such as 30 ° or 45 °), suitable for installation with limited space.

Mechanical reinforcement: For ultra long or large cross-section connectors, mechanical reinforcement extra flexible can be added to prevent sagging or vibration fatigue.

Surface treatment: In harsh environments such as humidity, salt spray, and corrosive gases, it is recommended to use 15 μ m tin plating or silver plating.

Installation and usage precautions

4.1 Optimal installation direction

Forissier strongly recommends installing the braided connector vertically (i.e. with the braided tape in the vertical direction). This can:

Avoid long-term bending deformation caused by gravity;

Beneficial for air convection and heat dissipation, reducing temperature rise;

Reduce the accumulation of dust and moisture.

If horizontal installation is unavoidable, ensure that the connectors have sufficient support or use reinforced types.

4.2 Spacing during Parallel Connection

When multiple braided tapes are connected in parallel in the same phase, the minimum spacing between connectors should not be less than the thickness of a single connector. A too small spacing can lead to increased mutual inductance effect, uneven current distribution, and increased heat dissipation difficulty.

4.3 Avoid copper wire damage

The flaring design of the terminal has reduced the risk of copper wire being crushed, but it is still necessary to avoid excessive bending or torque transmission to the braided tape during installation.

Use a torque wrench to tighten the bolts according to the required torque of the equipment. Tightening too tightly may fracture the copper terminal tube, while loosening too loosely may increase the contact resistance.

4.4 Temperature Monitoring

In practical operation, it is recommended to monitor the temperature of the hottest point of the connector through infrared temperature measurement or surface mount thermocouple. The surface temperature of bare copper connectors should not exceed 85 ° C, and tinned connectors should not exceed 105 ° C. If it exceeds, consideration should be given to:

Increase the cross-section or increase the number of parallel connections;

Reduce environmental temperature (improve ventilation);

Check for harmonic currents causing additional heating.

Common problems and troubleshooting

Possible causes and solutions for the problem phenomenon

Connector overheating (>85 ° C bare copper) with insufficient current carrying capacity; The parallel coefficient has not been taken into account; If the ambient temperature is higher than expected, recalculate the current carrying capacity, increase the number of parallel connections or choose a larger cross-section; Improve ventilation

Local high-temperature contact surface oxidation at the terminal; Loose bolts; The drilling size does not match the clean contact surface, apply conductive paste; Tighten again according to the torque; Check if the gasket is flattened

Micro motion wear caused by broken wires in woven tapes due to electric force; Excessive bending during installation is achieved by weaving fine threads (0.10 mm) to enhance flexibility; Increase mechanical reinforcement; Adjust installation angle

Surface corrosion (green or black) caused by corrosive gases in the environment; If the coating fails, use 15 μ m tin plating or silver plating instead; Replace with nickel plated or gold-plated terminals

Uneven current distribution in parallel connectors and differences in braided tape length; The terminal contact resistance is different; Ensure that the length of each connector is consistent when the spacing is too small; Use the same tightening torque; Increase spacing

Quick selection process

To help engineers quickly complete the selection process, please follow these steps:

Determine the required total current carrying capacity Itot (A) and ambient temperature Tamb (° C).

Determine whether to parallel: If Itot>maximum current carrying capacity of a single unit (such as 2000A), parallel connection is required.

Estimate the number of parallel connections n (usually 2-8).

Calculate the required current carrying capacity for a single unit, I2=Itot/coefficient (n) (refer to Table 2.3 for the coefficient).

Refer to Table 2.2: Find the minimum cross-section of ≥ I2 single in the corresponding ambient temperature and conductor type (bare copper/tin plated) column.

Confirm terminal size: Based on the selected cross-section, determine the recommended terminal A × B and drilling type from Table 3.2.

Confirm if special treatment is required: angled terminals, mechanical reinforcement, special coatings, etc.

Prepare order code: Forissier order code format is CSTP1000MMCRELT500, where:

CSTP: Tin plated copper (CSTN is bare copper)

1000: cross-sectional area mm ²

MMC: Terminal length 100mm, etc. (customized)

RELT500: Customer parameters such as center distance. Suggest providing complete drawings.