Cable lugs are electrical components used to safely connect wires and cable terminals to electrical equipment or terminate them. They are designed to easily and securely connect and disconnect electrical joints permanently or for maintenance. There are different types of cable lugs available for various electrical applications.
They are essential for using electricity across applications as they allow different electrical systems to connect. Therefore, one must account for the quality of material used, the correct type of lug, tools & dies used while crimping when installing cable lugs, as they play a crucial role in ensuring the durability and reliability of the joint. Cable lugs are made of copper or aluminium. Bimetallic Cable Lugs are of copper and aluminium, such as to avoid galvanic action, in which two dissimilar metals are in contact with each other causing corrosion of one metal on the other.
Classification of Cable Lugs:
A) Compression Type Lugs:
Here the connection is made by compressing the lug along with the cable to make a connection. The process is done by crimping the joint using appropriate crimping tools and dies. There is a lesser current loss in cable connections while using these cable lugs. Always use the exact crimping tool recommended by the cable lug manufacturer.
B) Mechanical Type Lugs:
A mechanical lug has a bolting mechanism on one end and a cable barrel for inserting the cable on the other. Here the connection is made by tightening the bolts using spanners or other fixing tools.
C) Cable Lug Design:
Cable lugs are designed such that one end of it is used for connecting to a cable, by soldering, welding, or crimping depending on the type of connection. The other end of the lug is then fastened to the terminal or connection point using a bolt, screw, or spring clip. The connector end of a cable lug is selected considering the compatibility with the terminal type and method of connecting it.
Procedure for Installing Cable lugs
Correct Identification of the Cable Lug:
Cable lugs are available in different sizes and specifications. There are four standards for them: The Indian Standards, DIN standards, BS Standards, and AS/NZ Standards.
Pre-requisites:
1) Before any electrical installation or maintenance activity, ensure that the persons involved follow safety precautions and personal protection equipment.
2) Identify the correct type of Cable lug for the particular electrical connection or application.
3) Choose the crimping tool with the exact dimensions recommended by the manufacturer of the cable lug. This can be done by checking the marking on the connector or from the labels on the packages.
Necessary Cable Preparation:
a) Using a suitable stripper remove the insulation to a distance equal to the insertion depth of the connector and leave suitable extra allowances (3mm to 5mm).
b) Clean or brush the surface of the cable or conductor to remove any oxides present.
Cable Lug Connection:
1) Insert the wire/cable/conductor into the barrel of the cable lug.
2) Ensure that the palm of the cable lug is oriented towards the terminal of the equipment, to which the connection is to be made.
3) Select suitable crimping dies and tools to ensure that the joints made are mechanically strong. Good joints provide efficient electrical connections.
4) Ensure proper crimping series.
5) Clean the surfaces of the connection to avoid resistance and corrosion.
6) Use appropriate nuts, bolts, washers for a firm and secure electrical connectivity.
Do’s:
a) Remove the cable insulation carefully, after removing the cable insulation do not cut or disturb any wire strand.
b) Confirm that cable strands have entered completely into the length of the barrel.
c) Use the complete barrel for crimping.
d) Ensure that all the wires are inserted into the long barrel.
e) Use only the recommended size of lugs for recommended size of cable.
f) In situations where multiple crimping is needed, do the crimping that is closer to the lug palm first.
Don’ts:
a) Do not strip cable insulation more than what is recommended.
b) Do not use mismatching crimping dies.
c) Do not use any other tool for crimping other than the recommended ones.
Proper Installation Procedure:
While installing cable lugs, it is imperative to specify and install the correct type of cable lug based on its application and compatibility to ensure safe and reliable results. Improper connections can lead to increased joint resistance that can cause fires. Therefore, the correct installation of cable lugs is crucial.
One can recognize the quality of lugs by their visual characteristics. For example, burr-free (without sharp edges) cable lugs with a flat palm and a cleanly shaped end are signs of a high-quality electrical connector. Despite the wide variety of cable lugs, each of them has a specific use and application stated by the manufacturer to avoid incompatible connections. The correct cable lug can ensure the safe installation of a permanent electrical connection.
Cable Preparation:
The cable is insulated and, the insulation layer needs to be stripped away for it to be connected with the cable lug. Use an insulation stripper instead of knives or pliers for best results, as specialized tools will minimize the risk of damaging or fraying wire strands of the cable that would lead to improper connections. The amount of insulation coating (to be removed) should be approximate to the depth of the barrel of the cable lug with some allowance of a few millimetres.
Cleaning the exposed wire before connecting it to the cable lug is mandatory. It can be done with a brush and should be done to each strand in the cable to ensure oxidation or tarnish is eliminated before use.
