As noted earlier, a 3 core cable is one that includes three conductors as part of the cable manufacturing process. Each type of cable has different uses, and it is typically not recommended that a specific use application switch and use a different cable. For example, if your ideal choice is for a 1mm 3 core cable, it might not be best practice to switch and use a thicker or thinner-gauge cable.
Typically, the 3 core cable is often the cable of choice for use for Appliance Class I connectivity. That’s because there is a requirement for such appliances (or related applications) to provide connectivity to earth. Using a 2-core wire instead of a 3 core electric cable for these applications may compromise the installation. Left un-earthed might expose users to electrical shocks.
Where there is no requirement for earthing, then electricians may use 2-core versions of a cable instead of a 3 core electrical cable. For example, in an application involving an Appliance Class II project, an engineer or electrician may use a 2-core braided cable instead of a 3 core braided cable. The reason for this usage is because Class II appliances generally do not require connectivity to earthing.
In summary, the cable used in an electrical application usually depends on whether there is a requirement for the equipment or appliance to be earthed. According to electrical codes, Class I appliances must have their chassis earthed. Use a 3 core mains cable to do this. The use of 2-core cable, on the other hand, is safe for Class II-type of applications.
The use of a 3 core & earth cable is advised for applications where there is a greater risk of electrocution if the live wire touches the body of equipment or appliance. For example, if the body is made from non-conductive materials, such as rubber, plastic, glass or ceramic, then it may not be essential to use 3 core cable.
However, it might be safe to choose outdoor 3 core cable, as opposed to 2-core wires, where the exterior is conductive, like metal, steel, iron or copper. You can use 2-core cables for non-conductive applications, but you must use 3 core cable for applications like bulb holders, lamp posts and any other use case where risk of electrocution is high.
Usually, a 3 core steel wire armoured cable (SWA) is used to transmit power underground, from the power generation source to a residence or commercial location. You may also see other armoured products, such as a 3 core 4mm armoured cable, used with a catenary wire in overhead power delivery applications. Generally, common electrical applications, such as lighting switches or power cords for appliances may use flexible wires, such as a 3 core flex cable. That’s because their use enables the cable to bend and twist without risk of breaking or splitting.
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