lab manual.rtf

Electrical workshop manual

A HAND BOOK FOR

ELECTRICAL WORKSHOP

Electrical and electronics engineering dept. SNIT adoor

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CONTENTS

Part 1 General

Syllabus

Electrical engineering - An overview

Electric power supply system

Part 2 Study of safety devices

Importance of safety devices

Circuit breakers MCB, MCCB & RCBO (ELCB) etc

Earthing systems

Symbols

Part 3 Experiments

One lamp controlled by one switch

One lamp controlled by one switch adding plug point 3.Two lamp controlled by two switch parallel

One lamp controlled by one switch adding plug point and bell

Two lamp controlled by one switch 6.Staircase wiring

Godown wiring

Hospital wiring

Fluorescent lamp wiring

10.wiring of DB With ELCB and MCB

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SYLLABUS

Study of wiring cables and electrical accessories Electrical and Electronics symbols.

Simple wiring circuits- A light is controlled by a single pole single throw (S.P.S.T) switch , addition of a plug point in the light circuit and addition of a calling bell in the wiring circuit.

Circuit with Fluorescent tube light

Circuits to control a lamp from two independent positions

Hospital wiring

Godown wiring

Wiring of D.B with ELCB and MCB.

Testing of circuits - testing of ON/OFF conditions using a tester, test lamp, and location of phase and neutral.

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Electrical engineering an overview

Electric current: - Electric currant can be termed as a continuous flow of electrons through a conductor. One ampere is the current produced when a pressure of one volt is applied across a circuit having one ohm resistance.

EMF: - EMF is electro motive force. Potential difference between two points in a circuit is the electrical pressure difference required to drive a current between them. Potential difference may be termed as voltage. Voltage of a torch battery is 1.5 V and that of automobile battery is 12V. KSEB supply voltage for domestic installation is 240 V.

Electric power (watt):- Electric power, P = Voltage * current * Power factor Unit of electric power is watt (W)

Electric energy:-Unit of electric energy is KWh (Kilo Watt hour) 1 unit energy = 1 KWh KSEB provides one KWh meter at every Installation for measuring consumed energy. Resistance is the property of a substance due to which it opposes the flow of current through it. Unit of resistance is ohm

Resistance, R = Specific resistance * I / A

Where I is the length of material & A is the area of cross section

Effect of temperature on resistance:-When temperature increases resistance of pure metals and Alloys increases when temperature increases resistance of electrolyte, insulators etc decrease.

Resistance in series:-Consider three resistors connected in series, and then the total resistance of the circuit will be the sum of the three resistors.

Ohms law:-Ohms law states that, the ratio of potential difference between any two points in a conductor to the current flowing between them is constant.

Study of Electric Power supply

Electricity: Electricity is a form of energy. Electricity is the flow of electrons. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power, Hydel power and other natural sources, which are called primary sources.

Electric power supply system

AC&DC: DC or direct current is steady current. It never changes its direction, and AC is alternating in nature. AC voltage can be increased or decreased with the help of transformers. By using high voltage AC, we can drastically reduce the transmission losses. AC can be converted into DC easily but reverse is not so easy. In India state electricity boards are the authorities to generate and distribute electric energy. KSEB generates electric power at a voltage of 11 KV. This power is transmitted by increasing the voltage at different levels as 33 KV, 66KV, 110 KV, 220KVor 400 KV from different substations. At load centers this voltage again stepped down as 11 KV and a feeder network is created. This feeder line energizes the 11KV/415V step down transformer, and from these

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transformers electric supply can be given to consumers at 240V and 415 V as single phase or three phases. All domestic and commercial consumers get electric energy from the distribution network of concerned electricity boards. Based on the power requirements of consumers Electricity Boards may give 3-phase connection (for high power) or single phase connection (for low power). In the three phase connections 4 wires are provided, where as in single-phase connection one phase and a neutral connection are provided to the consumers. Phase to neutral voltage in our country is 230 V and phase-to-phase voltage is 400 V of frequency 50 Hz. Most of the appliances work on single-phase supply. There are some motors, which requires three phase supply. A KWh meter is provided at the consumer end for measuring the electrical energy consumed. KSEB introduces different tariffs for different consumers, as per their connected load and nature of connection.

Study of safety devices

Importance of safety devices

The safety features are inbuilt with electric power distribution. The current is to flow through the path it is expected to pass and should not take another path through which it is not expected to pass. Conductors made of copper or aluminium are provided across the path for carrying the current and insulators like PVC, paper or rubber are provided

isolate the faulty circuit from the rest of the supply. The very high currents caused by short circuit situation can cause lots of damage to electrical installation. Protective devices are needed to break short-circuit and overload currents. Circuit breakers and fuses are protective devices that control the power going to a particular route of wiring. In case of an overload or a short on that circuit, the breaker or fuse trips and automatically shuts off power to that circuit. Fuses are the commonly used protection devices to protect components like wires, transformers electronics circuit modules against overload. The general idea of the fuse is that it "burns fuse link" when current gets higher than it's rating and thus stops the current flowing.

Types of safety devices _ Fuse

_ Circuit breakers( MCB, MCCB & ELCB) _ Earthing.

Basically two types of protections are provided in the power supply system of domestic consumers.

Protection from over current.

Protection from leakage current due to failure of insulation or inadvertent contact with live conductors by the user.

Over current and Short circuit

One type of situation that wiring needs to be protected against is over current. The electrical wiring is rated for certain maximum current. If you try to pull more current through it, the wiring will heat considerably. When the wiring heats too much, it will cause the melting of cable insulation, cause fire if there is something flammable near cable and even melt the copper conductors in the cable. So protection is needed to guarantee that in case of something tries to pull too much current through mains wiring, this cannot happen for any long time until the fuse blows and stops the current.

Every electrical circuit shall be protected against over current by suitable over current devices. These devices could be

Miniature Circuit Breaker (MCB)

Moulded Case Circuit Breaker

Semi enclosed rewirable fuses

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d. High Rupturing Capacity (HRC) fuses

Typical breaking capacities of protective devices are as follows:

HRC fuses - 80 kA

MCB - 16 kA

Rewirable fuses - 1 to 4 kA beats at a steady

FUSES

Fuse is a wire of short length having low melting point which gives protection against excessive current. This excessive current may be due to over load or short circuit. Under normal working condition the current flowing through the circuit is within safe limit. But when some faults such as short circuit occurs the current exceeds the safe limit value, the fuse wire gets heated and melts. This will cause breaking of the circuit. After one fusing operation, fuse wire must be rewired with the 2same size wire.

This basic guide will help you decide which fuse to fit to ensure the safe use of your household appliances.

Appliances up to 700 Watts = 3 Amp fuse Appliances between 700 and 1000 Watts = 5 Amp fuse Appliances over 1000 Watts = 13 Amp fuse

COMMON FUSE TYPES

1. Rewirable fuse

2. Cartridge fuse

3. HRC fuse

1. Rewirable fuse:

This is the cheapest method for protecting a circuit from short circuit. Wires of different diameters made of lead and tin are used in the circuit. When large current flows these wires melts and disconnects the faulty circuit from the rest of the supply. There are different types of fuses. The usual type is the rewirable type in which the fuse wire is carried in a removable fuse link (Fig. a). The fuse link is made of porcelain or other suitable insulating material. The fuse carrier is push-fitted to the fuse base to make the connection through. An advantage of this type is that the blown fuse wire can be replaced with negligible cost. But there is a chance of selecting a wrong size of fuse wire. Another disadvantage with rewirable fuse is

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that it may sometimes lead to fire hazards, when the fuse wire blows. The semi enclosed rewirable fuses has the following drawbacks:

It normally melts on 50 % to 100 % excessive overload. The melting current cannot be accurately predicted.

It takes time to rewire the fuse. Standard fuse wire should be always made available.

However it is the cheapest mode of protection from short circuit.

2. Cartridge fuse

Cartridge fuse consists of a tube with metal end caps at both ends. The tubeis usually made of glass with no filling material. The fuse wire is placed inside the tube, connected between the end caps. Since the tube is made of glass, the fuse element can be easily inspected for breakage. When the fuse is blown, the whole cartridge has to be replaced. The advantages of cartridge fuses are, quick and easy replacement and the fuse rating is marked on the end cap of the cartridge itself.Cartridge fuses are mainly: used in various electrical and electronic equipment.

3. High Rupturing Capacity Fuse (HRC):

This is a completely enclosed cartridge type of fuse. These fuses are screwed or linked in the circuit. Generally it is used in the high power circuits. High Rupturing Capacity (HRC) fuse consists of a porcelain tube! with metal end caps and fixing tags. The fuse element is

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held inside the tube between the end caps and the tube is filled with silica sand or granulated quartz. When the fuse element blows, the silica inside the tube prevent the formation of an arc, and thus avoids the possibility of fire hazards. HRC fuse links are available in a range of 10A to 800A.

The HRC fuse has the following advantages:

It is very reliable.

It has an enclosed fuse wire, therefore no chance its arc doing any damage to the surroundings.

It has low temperature rise at rated load. Maintenance free.

The drawbacks are:

It is costly. Take time to replace the fuse.

Circuit breakers

MCB and ELCB

MCB is miniature circuit breaker. It is automatic in action. When excessive current passes through the circuit, handle of MCB will moves down and thus trips the circuit. After one such an operation we can manually reset the supply by solving the fault in that circuit. Thus rewiring fault size fuse wire in the case of fuse can be avoided by using MCBs. ELCB is earth leakage circuit breaker. It protects the circuit from any leakage of current. It protects the circuit from lightning and thunder. Miniature Circuit Breaker (MCB) Miniature circuit breakers are compact devices used in distribution boards for protection against overload and short circuit. The overload protection is achieved by a thermal trip mechanism using a bimetallic strip. An electromagnetic trip mechanism is also incorporated for instantaneous tripping in the event of a short circuit. When there is a sudden increase in current due to a short circuit, the circuit should open immediately, but the bimetallic strip does not respond quickly. In this case, the solenoid attracts the plunger and thus triggers the trip mechanism. After clearing the fault, the MCB can be switched on manually. Fig. below shows the current path in a typical miniature circuit breaker when it is in the 'on' position. The current passes through a solenoid coil and a bimetallic strip.

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When an overload condition persists for a few seconds, the bimetallic strip bends and triggers the trip mechanism. The principle of operation of an MCB is based on the following two principles.

Thermal operation

Magnetic operation

Thermal operation

In thermal operation, the extra heat produced by the high current warms the bimetal strip. This results in bending the bimetallic strip and trips the operating contacts. The thermal operation is slow. Hence, it is not suitable for speedy isconnection required to clear fault currents. However, it is ideal for operation in the event of small but prolonged overload currents. Thus, in general the thermal operation is suitable for opening the circuit in the event of excessive current due to the overloaded machines.

The magnetic operation, on the other hand is suitable for protection against high short circuit currents. This magnetic operation is due to the magnetic field set up by a coil carrying the current, which attracts an iron part to trip the breaker when the current becomes large enough. The magnetic operation is very fast and is used for braking fault currents. In most cases of MCB' s, both types are provided so that overload currents and short circuit currents are handled with the same degree. It should however be remembered that the mechanical operation of opening the contacts takes a definite minimum time, typically 20ms, so that there can never be the possibility of truly instantaneous operation. In many installations, MCBs are preferred over fuses mainly because there is no need of rewiring the fuse wire or replacing the cartridge. MCBs are available in a range of 0.5A to 63A normal operating current and for the entire range, the, physical dimensions are almost identical.

The major advantages of MCBs are

Instantaneous opening of the contact on short circuit faults

Can be designed to operate even for very small overload currents They can be quickly reset by hand They cannot be reclosed if fault persist

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In many cases they preferred over fuses as there is no need to rewire it.

Earth Leakage Circuit Breaker

The earth leakage circuit breaker (ELCB) is a protective device, which will automatically trip, when there is an earth leakage within the installation. It is also known as residual current circuit breaker (RCCB). It works on the current balance principle. The main part is a core consisting of three windings. Here one winding carries the phase current, the other winding carries the neutral current and the third winding to the tripping circuit. Under normal operating conditions the net flux in the core is zero as such no emf induced in the trip coil. However, when earth fault occurs, the phase and neutral current varies, the net flux in the core will be different and as such, emf is induced in the trip coil and it is energized. It then opens the circuit. The functioning of the ELCB can be checked using a switch

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What is earthing /grounding?

Earthing or grounding is the term used for electrical connection to the general mass of earth. Equipment or a system is said to be 'earthed' when it is effectively connected

to the ground with a conducting object. Earthing provides protection to personal and equipment by ensuring operation of the protective gear and isolation of faulty circuit during:

Insulation failure Accidental contact

Lightning strike Importance of earthing

Earthing is necessary for proper functioning of certain equipments. Earthing is done also for preventing the operating personal from hazardous shocks caused by the damage of the heating appliances. Consider an electric heater connected to the supply using two-pin plug and socket. If by some chance the heating element comes in contact with the metallic body of the heater, the body of the heater being a conducting material will be at the same potential as the heating coil. If a person comes and touches the body of the heater, current will flow through his body, which will result in an electric shock.

System earthing: It is the earthing of neutrals of generating stations and substations. It is employed to limit the voltage of live conductors with respect to potential of general mass of earth. This is necessary to prevent failure of insulation.

Equipment earthing: Is earthing of non current carrying metal parts of electrical equipments. As per Rules 33 and 61 of Indian Electricity Rule 1956 non-current carrying metal parts must be earthed with two separate and distinct earth continuity conductors to an efficient earth electrode. However equipments with double insulation need not be earthed.

Some Definitions:

Earthing: A tower/ equipments connecting to the general mass of earth by means of an electrical conductor.

Earth Electrode: Connection to earth is achieved by electrically connecting a metal plate, rod or other conductors or an array of conductors to the general mass of earth. This metal plate or rod or conductor is called as "Earth electrode".

Earth lead: The conductor by which connection to earth is made.

Earth loop impedance: The total resistance of earth path including that of conductors, earth wire, earth leads and earth electrodes at consumer end and substation end.

Factors affecting the value of earth electrode resistance

Electrode material. Electrode size. Material and size of earth wire. Moisture content of soil. Depth of electrode of underground. Quantity of dust and charcoal in earth pit.

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Earth resistance consists of following components

Resistance of metal electrode Contact resistance between electrode and soil Resistance of soil away from electrode surface.

Distribution Board System

In distribution board system, which is most commonly adopted for distribution of electrical energy in a building, the fuses of various circuits are grouped together on a distribution board, some times simply known as fuse board. The two copper strips, known as bus-bars, fixed in a distribution board of hard wood or metal case are connected to the supply main through a linked switch so that the installation can be switched off as a whole from both the poles of supply if required. A fuse is inserted in the + ve or phase pole of each circuit so that each circuit is connected up through its own particular fuse. For determination of load of an installation the following ratings maybe assumed unless the values are known or specified.

Fluorescent lamps 40 watts. Incandescent lamps, fans, and socket outlets 60 watts. Power socket-outlets 1,000 watts. Exhaust fans as per capacity of exhaust fans.

SYSTEMS OF WIRING

The types of internal wiring usually employed in our country are: 1. Cleat wiring:

In this system of internal wiring the cables used are either VIR or PVC type. The cables are held by porcelain cleats about 6 mm above the walls or ceiling. The cleats are mademin two halves, one base and the other cap. The base is grooved to accommodate the cables and the cap is put over it and whole of it is then screwed on wooden plugs (gutties) previously cemented into the wall or ceiling. Thus the cables are firmly griped between the two halves of the cleats and secured to the supporting wall or

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ceiling. The cleats used are of different sizes and different types in order to accommodate cables of various sizes and different numbers of cables respectively. The cleats are of three typesone groove, two grooves and three grooves to accommodate one, two, and three cables respectively.

Advantages:

It is the cheapest system of internal wiring. Its installation and dismantlement is easy and quick. Material is recoverable after dismantlement. Inspection, alterations and additions can be easily made. Skill required is little.

Disadvantages:

It is not good looking. It is quite temporary and perishes quickly. The wires are exposed to mechanical injury.

The insulation catches dampness from the atmosphere and common salt like substance appears on the insulation which lowers the insulation

resistance and Causes leakage. Hence this system of wiring cannot be used in damp places.

Oil and smoke are injurious to VIR insulation.

Fields of Application:

The wiring of this type is very suitable for temporary installations in dry places. This is also acceptable where appearance is not so important and cheapness is the main consideration. This system is not suitable for use in domestic premises.

2. Wooden Casing and Capping Wiring:

The cable used in this type of wiring is either VIR or PVC or any other approved insulated cables. The cables are carried through the wooden casing enclosures. The casing consists of V-shaped grooves (usually two to hold the cables of opposite polarity in different groves) and is covered at the top by means of rectangular strip of wood,known as capping, of same width as that of casing. The capping is screwed to the casing by means of wooden screws fixed at every 15 cm on the centre fillet. To protect the casing against white ants first class seasoned teak wood, varnished hellac varnish is employed. Two or three cables of same polarity (either all phases or all neutrals) may be run in one groove and in no case the cables of opposite polarity should be run in the same groove. The casing ia usually placed 3.2 mm apart from the wall or ceiling by means of porcelain distance pieces of thickness not less than 6.5 mm in order to keep the casing dry at the back.

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3. CTS or TRS Wiring.

In this type of wiring the cables used may be single core, twin core or three core TRS cables with a circular oval shape. Usually single core cables are preferred. TRS cables are sufficiently chemical proof, water proof, steam proof but are slightly affected by lubricating oils. TRS eaoles are run on well seasoned, perfectly straight and well varnished (on all four sides) teak wood batten of thickness 10 mm at least. The width of the batten depends upon the number and size of cables to be carried by it. The battens are available in width of 13,19,25,31,38,44,50,56,63,69 and 75 mm. The wooden battens are secured to the walls or ceiling by flat head wood screws to wood or other approved plugs at an interval not exceeding 75 cm. The cables are held on the wooden batten by means of tinned brass link clips already fixed on the batten with brass pins and spaced at an interval of 10 cm in case of horizontal runs and 15 cm in case of vertical runs. The wiring after erection is neatly painted with two coats of oil-less noncracking paint as specified in IS 732 and so on.

Advantages

Its installation is easy and quick and saving in labor largely compensate for the extra cost of the cable.

Its life is long. Within certain limits it is fire proof. It can withstand the action of most chemicals such as acids and alkalies. It is cheaper than other types of wiring except cleat wiring. If the job is carried out with proper attention, it gives a nice appearance.

Disadvantages

Good workmanship is required to make a sound job in TRS wiring.

This type of wiring cannot be recommended for use in situations open to sun or rain unless preventive steps are taken to preserve the insulation of cables.

4. Lead Sheathed Wiring

This type of wiring employs conductors insulated with VIR and is covered with an outer sheath of lead aluminum alloy containing about 95% lead. This metal sheath gives protection to the cable from mechanical injury, dampness and atmospheric corrosion. The whole lead covering is made electrically continuous and is connected to earth at the point of entry to protect against electrolytic action due to leaking current and to provide safety against the sheath becoming a live. The cables are run on wooden batten and fixed by means of link clips as in TRS wiring. The great part of the cable employed is flat twin (the cable having two insulated conductors side by side covered with red and black tape respectively and under one flat covering of lead alloy). Three-core flat type cable is also used in certain cases as well as single core cables under a circular sheath

of lead alloy.

Advantages

It provides protection against mechanical injury better than provided by TRS wiring.

It is easy to fix and looks nice as it can be run in building without damaging decoration and can be painted to suit colour scheme of the surroundings. Its life is long if proper earth continuity is maintained throughout.

It can be use din damp situations provided protection against moisture effect on the ends of the cable is given.

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e) It can be used in situations exposed to rain and sun provided no joint is exposed.

Disadvantages

It is costlier than TRS wiring. It is not suitable for places where chemical corrosion may occur.

In case of damage to insulation the metal sheath becomes alive and gives shock, so as to provide safety against electrical shock it is necessary that the sheath is properly earthed and an earth wire is run side by side with it and all pieces are properly bounded or joined together so that not a single cover is left unearthed.

Skilled labour and proper supervision is required.

5. Conduit Wiring

In this system of wiring steel tubes, known as conduits, are installed on the surface of walls by means of saddles or pipe hooks or buried under plaster and VIR or PVC cables are drawn into afterwards by means of a GI wire of size of about 18 SWG. In damp situations the conduits can be spaced from the walls by means of small wooden blocks fixed below the pipes at regular intervals. In order to facilitate drawing of wires numbers of inspection fittings are provided along its length. The conduits should be electrically and mechanically continuous and connected to earth at some suitable point. The conduits used for this purpose are of two types namely (i) light gauge (or split type) conduit and heavy gauge (or screwed type) conduit. Light gauge or split conduit with a seam along its length is used for cheap work. It is not water tight or even damp proof and is not permitted on medium voltage (i.e. on voltages higher than 250V). Screwed conduit (solid drawn or with welded seam) is used for all medium voltage (250 V or 600 V) circuits and in places where good mechanical protection and absolute protection from moisture is desired. In general the finish of the conduit is black stove-enamelled, there being a smooth coating of enamel both on the inside and outside surface of the tube. Galvanized conduit is also employed, especially in damp situation when the conduit is on the surface but under ordinary conditions buried in walls it offers little, if any, advantage over good enamelled conduits.

Advantages

It provides protection against mechanical damage. It provides complete protection against fire due to short-circuits etc. The whole system is water proof. Replacement and alteration of defective wiring is easy. Its life is long if the work is properly executed.

It is shock proof also if earthing and bonding is properly done.

Disadvantages

It is very costly system of wiring. Its erection is not so easy and requires time. Experienced and highly skilled labour is required for carrying out the job.

Internal condensation of moisture may cause damage to the insulation unless the system outlets are properly drained and ventilated.

Fields of Application

As this system of wiring provides protection against fire, mechanical damage and dampness so this is the only approved system of wiring for:

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Places where considerable dust or puff is present such as in textile mills, saw mills, flour mills etc.

Damp situations. In workshops for lighting and motor wiring.

Places, where there is a possibility of fire hazards such as in oil mills, varnish factories etc.

Places, where important documents are kept such as a record room.

Residential and public buildings, where the appearance is the prime thing. The recessed type conduit wiring is preferred for residential and public buildings.

CHOICE OF WIRING

The following factors should be considered before selecting a particular type of wiring.

Safety: The first and foremost consideration is safety to a person using electricity against leakage or shock. Where there is a possibility of fire hazard,

conduit wiring is used.

Mechanical Protection: The wiring must be protected from mechanical

damage during use.

Permanency: The wiring must not deteriorate unduly by action of weather, fumes, dampness etc.

Appearance: The wiring should he good looking.

Durability: The wiring must be durable.

Accessibility: In wiring system there should be facilities for extension, renewal or alterations.

Initial Cost: The wiring selected should suit the pocket of the owner of the building.

Maintenance Cost: The wiring should have, as far as possible, the lowest maintenance cost.

The other factors, in addition to above, to be kept in view while making the choice of wiringis load voltage to be employed, type of building etc. Some of the most commonly used tools are described below:

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#To

ol Size Uses

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STUDY OF WIRING ACCESSORIES

Any device, associated with the wiring and electrical appliance of an installation, such as a switch, a fuse, a plug, a socket-outlet etc. is called the wiring accessory. The cables, flexible cords and various wiring accessories in common use are briefly described below.

Cables:

The cable or wire used in internal wiring is covered with insulation. The conductor is covered with insulation so that it may prevent leakage of current from the conductor and thus minimize the risk of fire and shock.

The wire employed for internal wiring of buildings may be divided into different groups according to

Conductor used number of cores used voltage grading and type of insulation used

According to the conductor material used in cables, these may be divided into two classes known as copper cables and aluminum cables.

According to the number of cores, the cable consists of, the cables maybe divided into the classes known as single core cables; twin core cables; three core cables; two core with ECC (earth continuity conductor) cables etc.

According to voltage grading the cables may be divided into two classes:

250/440 volt cables 650/1,100 volt cables.

According to type of insulation the cables are of the following types:

1. Vulcanized Indian Rubber (VIR) Cables:

VIR cables are available in 250/440 volt as well as in 650/ 1100 volt grades and are used for general electrical wiring in cleat, casing-capping and conduit wirings.

VIR cable consists of either tinned copper conductor or aluminum conductor covered with a layer of vulcanized Indian rubber insulation. Over the rubber insulation cotton tape sheathed covering is provided with moisture resistant compound bitumen wax or some other insulating material for making the cables moisture proof. The thickness of rubber insulation depends upon the voltage grade for which the cable is required.

The copper conductor is tinned to provide protection against corrosion due to presence of traces of sulphur, zinc oxide and other mineral ingredients in the VIR.

2. Tough Rubber Sheathed (TRS) or Cab Type Sheathed (CTS) Cables:

These cables are available in 250/440 volt grades and used in CTS'(or TRS) wiring. TRS cable is nothing but a vulcanized rubber insulated conductor with an outer protective covering of tough rubber. These cables are water proof, hence can be used in

wet conditions. These cables are available as single core, circular twin core, circular three core, flat three cores, twin core with an earth continuity conductor etc. In wiring of a three pin plug separate earth wire may be used, as it will be cheaper in cost and easy

in installation.

These cables are cheaper in cost and lighter in weight than lead alloy sheathed cables, described later and have the properties similar to those, of lead sheathed cables.

3. Lead Sheathed Cables:

These cables are also available in 250/440 volt grades and are used for internal wiring where climatic condition is not dry and has a little bit moisture. The lead

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sheathed cable is a vulcanized rubber insulated conductor covered with a continuous sheath of lead. The lead sheath provides very good protection against the absorption of moisture and sufficient protection against mechanical injury and so can be used without casing or conduit system. It is available as a single core, twin core, flat three core and flat twin core with an earth continuity conductor.

4. Polyvinyl Chloride (PVC) Insulated Cables:

These cables are available in 250/440 and 650/1,100 volt grades and are used in concealed wiring system. In this type of cable conductor is insulated with PVC insulation. Since PVC is harder than rubber so PVC cable does not require cotton tapping and braiding over it for mechanical and moisture protection.

Since the PVC is thermo-plastic insulation, so it is affected at high temperatures and it may soften and flow down. These cables cannot be used for giving connections to the heating appliances, pendant lighting etc. Though the insulation resistance of PVC is lower than that of VIR but its effect is negligible for low and medium voltages below 600 volts,

5. Weather Proof/Cables

These cables are used for outdoor wiring and for power supply or industrial supply. These cables are either PVC insulated or vulcanized rubber insulated conductors being suitably taped (only in case of vulcanized rubber insulated cable) braided and then compounded with weather resisting material. These cables are available in 250/440 volt and 650/1100 volt grades. These cables are not affected by heat or sun or rain. Although TRS cables can be used for outdoor purposes but due to their higher cost, weather proof cables are generally used for outdoor services.

6. Flexible Cords

A cable containing one or more cores, each formed of a group of wires, the diameter of cores and of the wires being very small to afford flexibility, is known as flexible cord. These are used as connecting wires for such purposes as from ceiling rose to lamp holder, or from socket-outlet to portable apparatus such as radios, fans, lamps,

heaters etc. The flexibility of such wires facilitate in handling the appliances and prevent the wires from breakage. The flexible cords used for house hold appliances are available in various pleasing colours, sizes and of various thickness of insulation. These wires should never be used for fixed wiring.

Switches

A manually operated device used for closing and opening or for changing the connections of a circuit is known as a switch. The switches used in internal wiring may be classified in various ways. According to the type of base material they are classified as porcelain or bakelite switches. According to colour of base they are either white or black or brown coloured switches. According to operation required, they are classified as one way, two-way, centre off, double pole etc.

1. One-way Switch

This type of switch consists of two terminals which can be easily seen from the back side of the switch as well, without removing the cover. The switch is always connected in series with the point (lamp, fan or socket-outlet) to be controlled.

2. Two-way Switch

The switch of this type consists of four terminals, two of them being short-circuited inside the switch. The switch of this type is usually used for the stair-case wiring or circuits where one point is to be controlled from two different places.

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3. Two-way Centre off Switch

The switch of this type is just like a two-way switch but having three operations. In the centre it becomes off. Such switches are used when two lamps are to be operated alternately.

4. Double Pole Switch

This is a combination of two one-way switches, which can be operated simultaneously as ON-OFF terminals of both the switches, are connected together by a handle made of bakelite. Such switches are used as interlinked switches when the load current is less than 5A and supply voltage is under250V.Incaseeither of the voltage or current exceeds the limits mentioned above DPI C switch is used.

5. Push-button Switches

Such switches are used for controlling the electric bells. When the knob is pressed, the circuit is completed and the bell rings and as soon as the knob is left, the circuit becomes open.

6.Table Lamp Switch

This is a small on-off switch which is commonly used in table lamps.

7. Bed Switch

Such switches are used to switch off the table lamps or other lamps while going to sleep or making the lamp on while getting up at night. It is connected in aeries with one of the two flexible wires. The specialty with this switch is that fluorescent material is applied to its knob so that it may glow at night and can easily be seen in darkness. This is a pendant type switch. The switches are of two types known as surface switches (or tumbler switches) and flush switches (or concealed switches).

i. Tumbler or Surface Switches

Tumbler switches are those which are fixed on the mounting blocks directly fixed on the surface of the wall. Such switches project out the surface of the wall and are in common use. Surface switches are available in round and oblong base. Round base switches are cheap and in common use. Oblong surface switches are good in appearance, but being costly, are rarely used.

ii. Flush Switches

Flush switches, as obvious from their name, are fixed in flush with the wall and do not project out. These switches are used where high quality performance and appearance are required.

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Ceiling Rose

The ceiling rose is used to connect the pendant lamps, fans or fluorescent tubes to the installation through flexible or silk covered wires. These are not used on a circuit, the voltage of which normally exceeds 250 volts.

Socket-Outlets

The socket-outlets are used to supply electrical connections whenever required for electrical appliances such as radios, table fans, table lamps, iron, stoves etc. Socketoutlets are of two types two pin type and three pin type. Two pin socket-outlets have become obsolete now-a-days. The three pin type socket-outlet has got three hollow terminals in which three pin plugs can easily be inserted but not loosely. Two holes being of same size, are meant for making connections to the flexible wire of the appliance and the third hole, which is bigger comparatively, is meant for earth connections. Thus three holes or sleeves are for live, neutral and earth connections. The three pin socketoutlets are also of two types:

5 A for table fans, table lamps, radios etc, and 15 A for power circuits as heater, stove, iron etc.

Plugs

Plugs are used to take the supply from the socket-outlets for electrical appliances

such as table lamp, table fan, heater etc. Similar to socket-outlets plugs are also of two types namely two pin and three pin. Two pin type plugs have become obsolete now-a-days. Three pin type plugs consist of three pins usually made from brass. To the two pins which are thin and of same size, flexible wires are connected and then covered up. To the third pin, which is thicker comparatively, earth wire from the electrical appliance is connected. Similar to 3 pin-socket outlets 3 pin plugs are also of two types5 A and 15 A.

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Lamp Holders

As the name indicates the function of lamp holder is to support the lamp and also to connect it electrically. These are designed for quick removal and replacement of the lamp. Lamp holders are of many types. A few will be described here. Lamp-holders may be either of brass or bakelite type with porcelain interior. Brass holders are more durable but may give shock if connections are poor. Though Bakelite holders are not durable, but do not give shock. The following are the different types of lamp holders

1. Batten Holders

Such lamp holders are used where the lamp is to he fitted to the roof or to the wall i.e. it is directly fitted either to batten or to wooden boards. Such lamp holders are bayonet type i.e. in such a lamp holder the lamp is forced in. turned slightly and left in position.

2. Pendant or Cored Grip Holders

Such a lamp holder is used when the lamp is to be suspended from the flexible cord. Such a lamp holder is hanged vertically downward from the ceiling with flu flexible cord, one end of which makes electrical connections with the ceiling rose and other with the lamp holder and thus with the lamp.

3. Angle Holders

Such lamp holders are used when the lamps are to be fixed directly on the walls and to give light at an angle. Such lamp holders are available in various fancy designs and colors.

4. Slanting Holders

Such lamp holders are used for lamps to be fixed on advertising boards, for flood lights and for stage lights. Such lamp holders are used along with shades (hand shape shades) so that light is concentrated on the material displayed and does not trouble the viewer.

5. Bracket Holders

Such lamp holders are used to give direct light in the room or above a particular place. These cannot be fixed on the roof or made to hang. Usually these are fixed on the wall. These may also be used in table lamps.

6. Water Tight Bracket Holders

Such lamp holders are provided with tubular glasses fixed with water tight cover. Such lamp holders are used outside the houses and for street lighting where

there is no cover to save the bulb from falling of water over it.

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Junction Box

In joint box system of wiring all joints in conductors are made by means of suitable connectors or joint cutouts in junction boxes. In looping back system of wiring, which is widely used now-a-days, junction boxes are not required.

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symbols

Positive

+

Negative

Earth

resistor

Variable resistor

inductor

Variable inductor

capacitor

Variable capacitor

Voltage source

voltmeter

wattmeter

motor

lamp

switch

transformer

generator

AC voltage source

SNIT ADOOR

Page 24


battery

Delta connection

Terminal

DC

AC

Overhead line

generator

Motor

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Exp no:1

Date:

One lamp controlled by one switch

Aim

To wire up a circuit with one lamp controlled by one switch in surface conduit system of wiring as per given layout. Prepare the list of material preferred as per the layout

Tools required

Screwdriver, linetester, cutting plair, wire stripper, hammer,hacksaw,pocker

Estimation

Sl

Name of material

Specification

quantity

no;

1

PVC flexible wire

2

PVCconduit

3

PVC saddles

4

Steady battern holder

5

Bulb

6

Fuse unit

7

Neutral link

8

SPST switch

9

3 way junction box

10

Round block

11

Switch box

12

Screws

Procedure

Wiring conduits are fixed on the board as per the given layout

The circuit consists of one SPST switch and one lamp holder

Make the circuit as per the given circuit diagram

Check the circuit before applying the supply

Give the single phase supply through a fuse and neutral through neutral link

Check the conditions

SNIT ADOORPage 26


Lay out

Circuit diagram

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Exp no;2

Date;

One lamp controlled by one switch adding plug point

Aim

To wire up a circuit with one lamp controlled by one switch with addition of plug point in surface conduit system of wiring as per the given layout. prepare the list of material preferred as per the layout

Tools required

Screw driver, line tester, cutting plier, stripper, hammer, hack saw, pocker

Estimation

Sl no;

Name of the material

Specification

Quantity

1

PVC flexible wire

2

PVC conduit

3


4

Switch SPST

5

Fuse unit

6

Neutral link

7

PVC saddles

8

Bulb

9

Plug point

10

3-way junction box

11

Switch box

Procedure

Wiring conduits are fixed on the board as per the given layout

The circuit consists of one SPST switch and one lamp holder with a plug point

Make the circuit as per the given circuit diagram

Check the circuit before applying the supply

Give the single phase supply through a fuse and neutral through neutral link

Check the conditions

SNIT ADOORPage 28


Lay out

Circuit diagram

SNIT ADOORPage 29


Exp no;3

Date;

Two lamp controlled by two switch parallel

Aim

To wire up circuit with two lamps controlled by two switch in surface conduit system of wiring as per the given layout

Tools required

Screw driver, line tester, cutting plier, hammer, pocker, wire stripper, hack saw

Estimation

Sl no;


Specification

Quantity

1

PVC flexible wire

2

PVC conduit

3


4

Junction box

5

SPST switch

6

Fuse unit

7

Neutral link

8

PVC round block

9

PVC saddles

10

Bulb

11

Switch box

12

screw

Procedure

Keep the material on the board as per the given layout

Fix the 4-way and 3-way junction boxes at the appropriate position

Fix the saddle clips and the conduit pipes

Lamp switch is also connected

The neutral required for the second lamp is tapped from the first lamp holder

Single phase supply is given and check the conditions

SNIT ADOORPage 30


Layout

SNIT ADOORPage 31


Circuit diagram

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Exp no;4

Date;


Aim

To wire up a circuit with one lamp controlled by one switch with addition of one plug point and one bell in the surface conduit system of wiring as per the given lay out

Tools

Screw driver, line tester, cutting plier, pocker, wire stripper, hack saw, and hammer

Estimation

Sl no;

Name of material

Specification

Quantity

1

PVC flexible wire

2

PVC conduit

3


4

SPST switch

5

Bell push switch

6

Plug point

7

Bell

8

Fuse unit

9

Neutral link

10

Saddles

11

Bulb

12

4-way junction box

13

3-way junction box

14

Cealing rose

15

Switch box

16

screws

Procedure

PVC pipes are cut into required size and fixed on board using PVC saddle clips

The PVC terminal boxes are fixed using PVC in appropriate position

The switches, plug and bell are fixed on the switch box and the lamp is connected in the lamp holder and bell push switch is also connected to the bell They are kept in PVC round block

The required amount of wire is cut and is put into the conduit pipes

SNIT ADOORPage 33


The fuse and neutral link are also connected in appropriate places

After the wiring is completed the line is tested using a tester

Layout

SNIT ADOORPage 34


circuit diagram

SNIT ADOORPage 35


Exp no;4

Date;


Aim

To wire up a circuit with one lamp controlled by one switch with addition of one plug point and one bell in the surface conduit system of wiring as per the given layout

Tools

Screw driver, line tester, cutting plier, pocker, wire stripper, hack saw and hammer

Estimation

Sl no


Specification

Quantity

1

PVC flexible wire

2

PVC conduit

3


4

SPST switch

5

Bell push switch

6

Plug point

7

Bell

8

Fuse unit

9

Neutral link

10

Saddles

11

Bulb

12

4-way junction box

13

3-way junction box

14

Cealing rose

15

Switch box

16

screws

Procedure

PVC pipes are cut into required size and fixed on the board using PVC in appropriate position

The PVC terminal boxes are fixed on the switch box and the lamp is connected in the lamp holder and bell push switch is also connected to the bell They are kept in PVC round block

The required amount of wire is cut and is put into the conduit pipes

The fuse and neutral link are also connected in appropriate places

After the wiring is completed the line is tested using a tester

SNIT ADOORPage 36


Lay out

SNIT ADOORPage 37


circuit diagram

SNIT ADOORPage 38


Exp no;5

Date;

Two lamp controlled by one switch series circuit

Aim

To wire up a circuit with two lamp controlled by one switch as per the given layout diagram

Tools

Screw driver, line tester, pocker, hammer, wire stripper, plier,mini hacksaw,chisel

Estimation

Sl no;


Specification

Quantity

1

PVC conduit

2

PVC flexible wire

3

Switch SPST

4

Saddle clips

5

Round block

6

Junction box

7

Switch box

8

Neutral link

9

Fuse unit

10


11

Bulb

12

screws

Procedure

Keep the material on the board as per the given layout and centralise them

Fix the 3-way junction box and switch box using screws

Connect them using conduit pipes and fix them using saddle clips

Fix the fuse unit and fix the neutral link

Wires are connected through the pipes as per the connection diagram

Switch on the supply after inserting the lamps into the holder

SNIT ADOORPage 39


circuit diagram

SNIT ADOORPage 40


Exp no;6

Date;

Staircase wiring

Aim

To wire up a circuit with one lamp controlled simultaneously from 2 places as per the given layout diagram in conduit system satisfy the conditions

S1

S2

L off

S1

S2

L Bright

S1

S2

L Bright

S1

S2

L off

Tools

Screw driver, line tester, pocker ,hammer, wire stripper, plier, mini. Hack saw, and chisel

Estimation

Sl no;


Specification

Quantity

1

PVC conduit

2

PVC flexible wire

3

Switch SPST

4

Saddle clips

5

Round block

6

Junction box

7

Switch box

8

Neutral link

9

Fuse unit

10


11

Bulb

12

screws

Procedure






SNIT ADOORPage 41



SNIT ADOORPage 42


circuit diagram

SNIT ADOORPage 43


Exp no;7

Date;

Godown wiring

Aim

To wire up a circuit with three lamps controlled by three switches in godown wiring. Also prepare the list of material required as per the given layout

S1

S2

S3

L1

L2

L3

ON

OFF

OFF

OFF

ON

OFF

OFF

OFF

ON

OFF

ON

OFF

OFF

OFF

OFF

ON

OFF

OFF

Tools


Estimation

Sl no;


Specification

Quantity

1

PVC conduit

2

PVC flexible wire

3

Switch SPST

4

Saddle clips

5

Round block

6

Junction box

7

Switch box

8

Neutral link

9

Fuse unit

10


11

Bulb

12

screws

SNIT ADOORPage 44


Procedure







SNIT ADOORPage 45


circuit diagram

SNIT ADOORPage 46


Exp no;8

Date;

Hospital wiring

Aim

To wire up a circuit with two lamps controlled by two switches also conditions are satisfied in the hospital wiring system . Also prepare the estimation

S1

S2

L1

L2

dark

dark

dim

dim

bright

dark

bright

bright

Tools


Estimation

Sl no;


Specification

Quantity

1

PVC conduit

2

PVC flexible wire

3

Switch SPST

4

Saddle clips

5

Round block

6

Junction box

7

Switch box

8

Neutral link

9

Fuse unit

10


11

Bulb

12

screws

SNIT ADOORPage 47


Procedure







SNIT ADOORPage 48


circuit diagram

SNIT ADOORPage 49


Exp no;9

Date;

Fluroscent tube

Aim

To design estimate and wire up circuit containing fluroscent controlled by switch in PVC conduit system of wiring

Tools

Screw driver, wire stripper, line tester, pocker, and knife

Estimation

Sl no;


Specification

Quantity

1

PVC conduit

2

PVC box

3

Saddle clip

4

PVC flexible wire

5

Tube frame

6

Tube holder

7

Kitkat fuse

8

Neutral link

9

Chock

10

SPST switch

11

Starter

12

Ceiling rose

Procedure

Each coil of the end coil is connected by a wire

This wire is connected to chock

Chock output is connected to the connector

Give phase to chock wire and neutral is the other

In this phase wire a one way switch is also connected

The fluorescent tube is inserted to the end coil socket field in the tube fitting

The one way switch is put in position ON

Then fluorescent lamp will glows

SNIT ADOORPage 50


Circuit diagram

SNIT ADOORPage 51


Exp no;10

Date;

Wiring DB with ELCB and MCB

Aim

To design and wire up the circuit of main board and a consumer load having ELCB and MCB for a bed room having one light point. Work is to be done in PVC conduit system as per the given layout and prepare suitable estimation

Tools required

Pocker, hammer, screw driver, wire stripper, plier, hack saw, and line tester

Materials required

Sl no;


Specification

quantity

1

PVC flexible wire

2

PVC conduit

3

SPST switch

4

Bulb

5

Energy meter

6

Isolator

7

ELCB

8

MCB

9

MCB

10

Round block

11

Switch box

12

Screws

Procedure

The components are laid on the board and arrange according to the connection diagram

The whole arrangement is centralised

Draw wire through the pipes and connection are made in main board and consumer board

Neutral and phase wire are connected and connections are taken to sub-circuit

SNIT ADOORPage 52


Layout

SNIT ADOORPage 53

lab manual.rtf

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