Electric work 02 -Electrical cables and fittings

Electrical cables 

Electrical cables are used to transmit electricity, and they are made up of two or more wires bonded together (through twisting or braiding). These wires are covered by protective and insulating material. There are many different types of electrical cables, and they are typically categorized depending on such factors as electrical conductivity, type of insulation, type of protector (or covering), weight, cost, and specific uses.


Other factors that determine the type of electrical cables include voltage rating, type of protective covering, fiber core size, cable weight and cable diameter.

• A cable is an assembly of one or more conductors (wires) with some flexibility.
• A lead is a complete assembly of cable and connectors.
• A wire is a single conductor which may have an outer layer of insulation (usually plastic).

Types of cables

• Single and multi-strand conductors

Solid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. 

        Multi-strand wire                                                                Single –strand wire

Stranded wire or multi strand conductor is composed of a bundle wires to make a larger conductor.

Stranded wire is more flexible than solid wire of the same total cross-sectional area. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. Solid wire also provides mechanical ruggedness; and because it has relatively less surface area which is exposed to attack by corrosives, protection against the environment. 

Stranded wire is used when higher resistance to metal fatigue is required. Such situations include connections between circuit boards in multi-printed-circuit-board devices, where the rigidity of solid wire would produce too much stress as a result of movement during assembly or servicing; A.C. line cords for appliances; musical instrument cables; computer mouse cables; welding electrode cables; control cables connecting moving machine parts; mining machine cables; trailing machine cables; and numerous others.

Single-cored and multi-cored cables

Single core

Single core cable is mostly used for industrial applications where it is run in conduits. In domestic wiring it is usually only used for certain situations such as for electric fittings. 

Multi Core

Colours used for the cable insulation 

Electrical wires have markings stamped or printed on the outside sheath of the cable. These markings tell what type and size of wire that you have. And also the color of the wires inside of the sheath reveals that different color wires serve different purposes.

Purpose	Colour
Protective earth (PE)	Green/yellow bi-colour
Neutral (N)	Blue
Single phase: Live (L) Three phase: L1	Brown
Three phase: L2	Black
Three phase: L3	Grey

Flexible cables colour code

No. of cores	Colours
2 core	Brown , Blue
3 core	Brown , Blue , Green and yellow
4 core	Brown , Blue , Green and yellow , Black or grey
5 core	Brown , Blue , Green and yellow , Black or grey , Black or grey

Basic types of electrical accessories used for domestic single phase circuits.

Mounting Box

Mounting boxes protect connections between two or more wires or between wires and switches or fixtures. Mounting boxes are available with different sizes and made of different materials such as ABS, plastic , PVC and etc…

Switches

An electrical switch controls the flow of power in an electrical circuit. It provides an open circuit in the off position and acts as a closed circuit in the on position.

Types of switches

·        

Single Pole Switches  

This is the simplest type of switch. Most residential switches are single pole switches.

	Single pole switch with neon indicator		Single pole switch without neon indicator

 

·       Double Pole Switches

 

These types of switches are often used to switch mains electricity because it can isolate both the live and neutral connections at once.

Socket outlet

Socket outlets are used when temporary electrical connections are required. eg : for connecting table lamp , table fan , radio ,etc……There are two types of socket outlets available in the market.

       I.            Two pin type (live, neutral)

    II.            Three pin type ( live , neutral and earth)

As all appliances connected by flexible leads should be earthed, two pin type is outdated today. The 3 pin type is standardized for domestic wiring and use at 2,5,13 and 15 A rating.

Ceiling rose

Ceiling rose is used to connect pendant lamps, ceiling fans and etc… to the supply system. Ceiling rose consist of two main parts called base and cover. Both the parts are made up of Bakelite or porcelain. Terminals are provided on the base and a hole is made in the cover to take out the flexible wire.

 

Junction box

Junction boxes are used in electrical installation to join some conductor and provide different paths for different conductors. Most of the junction boxes are made of plastic.

Cable clips

Cable clips are used to attach electrical cables to a wall or baseboard. Based on the cables that are used, suitable type of cable clips should be selected.

  

    

           

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