Cable lug

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In electrical installation technology, cable lugs enable cables or strands to be electrically connected using screws (ring, fork) or plugging (flat plug connector) .

In contrast, wire end sleeves are often required to fasten cables in terminals . Solid conductors can also be screwed on directly by bending the wire into an eyelet. There are also crimp rings in which the strand is inserted in a ring for screw fastening of stranded wires. Solder lugs that can also be used for this are not referred to as cable lugs.

Cable lugs designed as a ring or fork enable terminal contact to be made on electrically conductive components with a screw that is connected to this component and makes terminal contact with one or more cable lugs.

Various types of cable lugs and ferrules

species

Cable lugs for pressing (left for 22 to 16  AWG , next to 10 mm 2 ), right for screwing for 35 mm 2 conductor cross-section

There are essentially three different types of cable lugs. In addition to the types with a screwed sleeve, these are:

Crimp cable lugs

In the case of crimp cable lugs, the conductor holder is formed by a sheet metal that is bent upwards at the side. When crimping , this area, including the conductor end, is placed in a crimping tool or machine. This bends the sheet metal tabs inwards and downwards onto the end of the conductor, resulting in a kidney-shaped cross-section.

Often there are two more sheet metal tabs at the end of the conductor insulation so that strain relief and kink protection can be created there in the same way. Both crimping operations can either be carried out separately (crimping pliers with adjacent dies) or simultaneously. The dies for both crimps are arranged one behind the other in the crimping tool.

In the case of insulated crimp cable lugs, this area is under an insulating sleeve through which the pressing force acts. When crimping, the extended end of this insulating sleeve is pressed around the insulated area of ​​the cable at the same time, so that kink protection is formed. The insulating sleeve of insulated cable lugs has a color that characterizes the cross-section.

Colors according to DIN 46245:

  • Red for cross-sections from 0.5 to 1 mm 2
  • Blue for cross-sections from 1.5 to 2.5 mm 2
  • Yellow for cross-sections of over 4 to 6 mm 2

Compression cable lugs

Compression cable lugs have a thicker, tubular cable lug, which is closed, sleeve-shaped conductor receptacle, which is deformed with crimping pliers, so that a positive and positive connection is formed with the conductor. There are different crimping pliers for certain cross-sectional areas, as the cross-section of the sleeve must match that of the conductor, and different shapes (hexagonal cross-section or one or two blunt mandrels that press the sleeve onto the conductor in a cone-like manner).

A special design of compression cable lug in combination with a plug are the flat plugs commonly used in automotive electrics in combination with a compression cable lug. This cost-effective design comes in various sizes as both a plug and a socket and enables an electrical connection to be easily disconnected for service purposes. This design is also known colloquially under the registered trade name Faston or as a Faston connector .

Compression cable lugs are used for copper conductors, but also especially for aluminum conductors (large cross-sections in power networks).

Assembly

A cable end to be provided with a cable lug is first stripped in its end area. The stripping length and the usable conductor cross-sections are specified by the manufacturer for each cable lug. A cable lug is then placed on the stripped end area. Crimp and compression cable lugs are then deformed using special crimping or compression pliers or a press with a corresponding die . In this way, a force fit and an electrically conductive connection between the cable and the cable lug is ensured.

Crimping pliers often leave a mark in the cable lug, they have an engraving in the die for this purpose. This is for quality control.

  • The three working steps in pressing

  • A cable lug in a crimping tool during the crimping process

  • A ready-pressed cable lug with crimped identification, plus the pliers with the corresponding engraving

  • Two cable lugs; before (left) and after pressing (right)

Soldered connections are rarely used, as properly executed crimp and press connections are much more reliable.

Tools

Two medium quality pliers for cable shoe assembly; Crimping pliers above for uninsulated open cable lugs, below crimping pliers for insulated cable lugs (color codes red, blue, yellow)

Crimping and pressing pliers are special tools for small quantities. You and also mechanized solutions have one or more dies for processing one or more cross-sections of a certain cable lug type.
The pliers often have a device that only releases the cable lug again when the required pressure has been applied.

In production, crimp and compression cable lugs are assembled with presses (inserted by hand or fully automated including stripping). For mobile use when working on the power grid, there are motorized hydraulic presses in order to be able to press large cross-sections on site.

literature

  • Volker Behrens: Electrical contacts: materials, designs and applications in communications, automotive and energy technology . 3. Edition. Expert-Verlag, 2010, ISBN 978-3-8169-2292-6 .

Individual evidence

  1. ↑ a b c Insulated flat receptacles, tin-plated bronze. Retrieved June 7, 2019 .