Engineering Practice Lab Electrical

V.BALAJI, M.Tech, (Ph.D), AP/EEE,DCE. Page 1

DHANALAKSHMI COLLEGE OF ENGINEERING

GE 1X03 ENGINEERING PRACTICES LAB

(ELECTRICAL)

LIST OF EXPERIMENTS

1. Residential House Wiring Using Switches, Fuse, Indicator Lamp And Energy

Meter

2. Calibration Of Ammeter

3. Calibration Of Voltmeter

4. Measurement Of Power Using Wattmeter

5. Measurement Of Power Factor

6. Measurement Of Resistance To Earth Of Electrical Equipment

7. Staircase Wiring

8. Tube Light Wiring

9. Study Of Electric Iron-Box


RESIDENTIAL HOUSE WIRING USING SWITCHES,

FUSE, INDICATOR LAMP AND ENERGY METER

AIM:-

To make simple residential house wiring using switches, fuse, indicator, filament

lamps and energy meter.

APPARATUS REQUIRED:-

Wiring Board

Connecting Wires

Lamps

Fuse

Indicator

Energy meter

THEORY:-

A switch is used to make or break the electric circuit. It must make the contact finely.

Under some abnormal conditions it must retain its rigidity and keep its alignment

between switch contacts. Different types of switches are as follows.

1. Surface or Tumbler switch

a. Single way switch

b. Two way switch

2. Flush Switch

3. Pull or Ceiling switches

4. Rotary snap switches

5. Push button switch

6. Iron- Clad watertight switches

The fuse arrangement is made to break the circuit in the fault or overloaded conditions.

The energy meter is measuring the units (KWhr) consumed by the various loads.


CIRCUIT DIAGRAM:-

PROCEDURE:-

1. Mark the bulb and switch positions.

2. Give the connections as per the circuit diagram.

3. Switch on the supply.

4. Check the lamps are glowing or not in the corresponding switches are kept in

the ON position.

5. Check whether the energy meter responding to the load.

RESULT:-

Thus the simple house wiring by using switches, fuse, indicator, filament lamps and

energy meter was studied.

Viva Questions:

1.What are the different types of house wiring used in non-industrial premises?

2.What are the advantages of non metallic PVC wiring?

3.What are the accessories used for conduit wiring?

4.How the selection of size of the cable is decided?

5.What are the types of lamp holder?

CALIBRATION OF AMMETER

230 V 50 HZ Single phase AC Supply

D P S T S

P

N

10 A Fuse 10 A Fuse

1φφφφ Energy meter M L C V

Indicator Lamp Lamp 2 Lamp1

Switch 1 Switch 2


Aim:

1. To measure the current in a given circuit by standard ammeter and to calibrate

the nonstandard ammeter by using the standard ammeter.

2. To find the error and percentage error in the given ammeter with respect to the

standard ammeter.

Apparatus required:

1. Single phase autotransformer 1 KVA ()

2. Standard Ammeter (0-10A) MI

3. Nonstandard Ammeter (0-10A) MI

4. Lamp load

Formula used:

1. Error = AS – AN

AN – Nonstandard Ammeter reading

AS – Standard Ammeter reading

2. % Error = (AS – AN)X100/AS

Circuit Diagram Tabular Column S.No Standard Ammeter Nonstandard Ammeter Error Percentage Error

D P S T S

230 V 50 HZ single phase AC

V

(0-300)V MI

1 – Phase, 230V /(0-270) V Auto Transformer

10 A

10 A

P A

(0-10) A MI Non - Std

LAMP LOAD N

A

(0-10) A MI Std


reading (AS) reading (AN) (AS -AN) (AS – AN)X100/AS

Model Graph Procedure:

1. Make the connections as per the circuit diagram.

2. The autotransformer is varied to the rated voltage.

3. The readings on the standard and nonstandard ammeter are noted by varying

the lamp load.

4. The readings are tabulated.

Result:

Thus the current in the circuit was measured by the standard ammeter and the non

standard ammeter was calibrated.

Viva Questions

1. State the type of Ammeter

% Error (in %)

Current Ic (in Amp)


2. How the Ammeter to be connected in a circuit

3. State the purpose of Autotransformer in the circuit

4. State the reasons for error in Ammeter

5. State the precaution to be observed when conducting the experiment.

CALIBRATION OF VOLTMETER

Aim:

1. To measure the voltage in a given circuit by standard voltmeter and to

calibrate the nonstandard voltmeter by using the standard voltmeter.


2. To find the error and percentage error in the given voltmeter with respect to

the standard voltmeter.

Apparatus required:

1. Single phase autotransformer 1 KVA

2. Standard voltmeter (0-300) V MI

3. Nonstandard voltmeter (0-300) V MI

4. Lamp load

Formula used:

1. Error = VS – VN

VN – Nonstandard Voltmeter reading

VS – Standard Voltmeter reading

2. % Error = (VS – VN)X100/VS

Circuit Diagram Tabular Column S.No Standard Voltmeter

reading (VS) Nonstandard Voltmeter reading (VN)

Error (VS -VN)

Percentage Error (VS -VN)X100/VS

230 V 50 HZ single phase AC Supply

V

V

(0-300V) MI Non - Std (0-300V) MI

Non - Std

1 – Phase, 230V /(0-270) V Auto Transformer 10 A

10 A P

N

D P S T S


Model Graph Procedure:

1. Make the connections as per the circuit diagram.

2. The autotransformer is varied and the readings on the standard and

nonstandard voltmeter readings are taken.

3. The readings are tabulated and the percentage error is calculated.

Result:

Thus the voltage in the circuit was measured by the standard voltmeter and the

non standard voltmeter was calibrated.

Viva Questions

1. State the type of voltmeter

2. How the voltmeter to be connected in a circuit?

3. State the purpose of Autotransformer in the circuit

4. State the reasons for error in voltmeter

5. State the precaution to be observed when conducting the

Voltage Vc (in Volts)

% Error in %


MEASUREMENT OF POWER USING WATTMETER

Aim:

To measure the power in the AC circuit with the help of a single-phase wattmeter.

Apparatus required:

1. Single phase autotransformer 1 KVA, (0-300V)

2. Wattmeter 300V, 10A UPF

3. Connecting wires

4. Lamp load

5. Voltmeter (0-300) V MI

6. Ammeter (0-10) A MI

Formula used:

1.Indicated value of power = Measured value X Multiplication factor

2.Actual power = VI Cosφ Watts

Where, V-Voltmeter reading

I - Ammeter reading

Assumed power factor Cosφ = 1

3. % Error = Indicated power-Actual power X 100 Actual Power


Circuit Diagram Tabular Column Multiplication factor =

S.No Voltage Volts

Current (Amp)

Wattmeter reading (Watts) Actual Power (Watts)

% Error

Measured Value

Indicated value

Model graph

D P S T S

230 V 50 HZ Single phase AC Supply

V

(0-300V) MI

1 φφφφ, 230V /(0-270) V Auto Transformer

10 A

10 A

P A

(0-10) A MI

LAMP LOAD

300V,10A,UPF,Watt Meter

N

C V

L

% Error (in %)

Current I (in Amp)


Procedure:

1.The circuit connections are made as per the circuit diagram.

2. Initially no load is applied

3.The autotransformer is varied to the rated voltage.

4.The values of voltmeter, ammeter and wattmeter on no load condition is noted.

5.By varying the load in steps the corresponding readings of ammeter, voltmeter

and wattmeter are noted.

6.The % Error is calculated.

Result:

Thus the power in the circuit was measured by the wattmeter and the % error was calculated.

Viva Questions

1. Mention two types of wattmeter 2. How are current coil terminal of a wattmeter identified 3. How are pressure coil terminal of a wattmeter identified 4. If wattmeter pointer tends to deflect in the reverse direction, what is the action to

be taken 5. What is meant by Multiplication Factor as applied to wattmeter 6. State precautions to be observed while conducting the experiment


MEASUREMENT OF POWER FACTOR Aim :

To measure power factor for the load in the given circuit.

Apparatus required:

1. Single phase autotransformer 1 KVA , 230/(0-270)V

2. Voltmeter (0-300)V, MI

3. Ammeter (0-10)A MI

4. Wattmeter 300V, 10A, UPF

5. Load

6. Connecting wires

Theory:

The numerical value of cosine of the phase angle between the applied voltage and

the current drawn from the supply voltage gives the power.

It is denoted by cosφ.

For pure resistive circuit power factor value is 1 and for pure inductive or

capacitive circuits power factor is 0. For the other combinations the power factor is

defined as lagging or leading i.e whether the resultant current lags or leads the supply

voltage.

Circuit Diagram

D P S T S

230 V 50 HZ single phase AC

V

(0-300V) MI

1 – Phase, 230V /(0-270) V Auto Transformer

10 A

10 A

A

(0-10) A MI

LAMP LOAD

300V,10A,UPF,Watt Meter

N

C V

L M P


Tabular Column Multiplication factor =

S.No Voltage Volts

Current (Amp)

Wattmeter reading (Watts) Power factor

Measured Value

Indicated value

Formula used:

Power measured by wattmeter = VI cosφ

Actual power = VI

V - Voltmeter reading in volts

I - Ammeter reading in Amps

Power factor cosφ = Power measured by wattmeter (VI cosφ)

Actual Power (VI)

Procedure:

1.The circuit connections are made as per the circuit diagram.

2.The autotransformer is varied to the rated voltage.

3.The values of voltmeter, ammeter and wattmeter are noted for the various load

conditions

4.Finally by using the formula the value of power factor is calculated.

Result:

Thus the power factor in the given circuit was measured.


MEASUREMENT OF RESISTANCE TO EARTH OF

ELECTRICAL EQUIPMENT

Aim:

To measure the resistance to earth / insulation resistance of the order of mega ohms.

Theory:

For this experiment we have to use the Megger. Is is an instrument for testing the

insulation resistance of the order of mega ohms.

Principle:

A megger consists of an emf source and a voltmeter. The voltmeter scale is

calibrated in ohms. In measurement, the emf of the self-contained source should be equal

that of the source used in calibration.

The deflection of the moving system depends on the ratio of the currents in the coils

and is independent of the applied voltage. The value of unknown resistance can be found

directly from the scale of the instrument. Figure shows detailed diagram of a megger. It

consists of a hand driven dc generator a emf about 500v.the permanent dc meter has two

moving coils. First one is deflecting coil and another another one is controlling coil. The

deflecting coil is connected to the generator through a resistor R2 . The torque due to the

two coils oppose each other. It consists of three terminals E (earth terminal ) and L (line

terminal) and G (guard wire terminal).


Operation:

When the terminals are open circuited, no current flows through the deflecting coil.

The torque to the controlling coil moves the pointer to one end of the scale. When the

terminals are short circuited, the torque due to the controlling coil and the pointer is

deflected to the other end of the scale i.e. zero mark. In between the two extreme

positions the scale is calibrated to indicate the value of unknown resistance directly. The

unknown insulation resistance is the combination of insulation volume resistance and

surface leakage resistance. The guard wire terminal makes the surface leakage current to

by pass the instrument hence only insulation resistance is measured.

Result:

Thus the measured value of the resistance to earth / insulation resistance of the unknown

material is = ----- MΩ



Procedure:

1.Mark switch and bulb location points and draw lines for wiring on the wooden board.

2. Place wires along the lines and fix them with the help of clamps

3. Fix the two-way switches and bulb holder in the marked positions on the wooden

board.

4. Complete the wiring as per the wiring diagram.

5. Test the working of the bulbs by giving electric supply to the circuit.

Result

The staircase wiring is completed and tested.


TUBE LIGHT WIRING

Aim

To prepare wiring for a fluorescent tube light with switch control.

Tool required

1. Screw driver

2. Hammer

3. Cutting Plier

4. Line tester

Components required

1. Switch

2. Tube light with fitting

3. Joint clips

4. Wires

5. Screws

6. Switch board

FLUORESCENT LAMP WIRING:-

230V,1φ

50Hz,ACP N

STARTER

CHOKE


Working of the Fluorescent tube light

The fluorescent lamp circuit consists of a choke, starter, a fluorescent tube and a

frame. The length of the commonly used fluorescent tube is 100cm and its power rating is

40W and 230V.

The tube is filled with argon and a drop of mercury. When the supply is switched

on, the current heats the filaments and initiates emission of electrons. After one or two

seconds, the starter circuit opens and makes the choke to induce a momentary high

voltage surge across the two filaments. Ionization takes place through argon and produces

bright light.

Procedure

1. Mark the switch and tube light location points and draw lines for wiring on the

wooden board.

2. Place wires along the lines and fix them with the help of clips.

3. Fix the switch and tube light fitting in the marked positions.

4. Complete the wiring as per the wiring diagram

5. Test the working of the tube light by giving electric supply to the circuit.

Result

The wiring for the tube light was completed and tested.


STUDY OF ELECTRIC IRON-BOX

The electric iron is used to iron the clothes. It is of two types (a) ordinary electric iron (b)

automatic type.

Ordinary Iron

It has following main parts: Sole plate, heating element, pressure plate, hood

assembly

Sole Plate: It is made of cast iron and its bottom is nickel plate which is very shining like

glass. The top of the plate has a smooth surface and two has threaded holes.

Heating Element: The heating element is made from flat nichrome wire wound on a

mica sheet. The bottom and the top of the element is covered with thick mica sheets and

are riveted with the element. The elements are available to different wattages like 450,

750 and 1000 Watt. The element of ordinary iron differ from the element used in

automatic iron in construction and wattage. In ordinary iron 450W or 750W element is

used. Whereas in automatic iron 750W or 1000W element is used.

Pressure Plate: The pressure plate is made of cast iron. Its shape resembles with the

heating element. Pressure plate sets and presses the element on sole plate with the help of

two machine screws and nuts. It must be tightly fitted. If this plate is kept loose, the

element will fuse quickly. The surface bottom side of the pressure plate must be smooth

like sole plate. Any projected portion in any of the two plates pressure plate and sole

plate, will fuse the element quickly.


Hood Assembly: It is used to cover all the above stated parts. It is made of iron sheet

with nickel plating. Terminal box to give connection to the element is also housed in the

handle in many irons and in iron sheet in many other types. For readymade handles are

available in the markets.

Automatic Iron

In such iron box the extra part than the ordinary iron is the thermostat assembly

which disconnects the supply from the element automatically when the press reaches its

preset heat range. This iron is costlier than the ordinary iron. A dial knob is fitted outside

and on the cover and under the handle. On this dial cotton, rayon, woolen words are

written. By giving rotation the knob is set accordingly. When the iron temperature

increases beyond the preset limit, the thermostat opens a pair of contact point to interrupt

the current flow. Then when the temperature drops below the preset limit, the thermostat

recluses the contact points. Turning of heat control knob place more or less pressure on a

spring. This then determines how far the thermostat must warm before the contacts open

and thus what temperature is required for this action. The figure shows the wires, iron

connector, plug and an ordinary iron.


Result


Engineering Practice Lab Electrical

Documents

calibration of ammeter

type of ammeter v

vs standard voltmeter

given ammeter

fuse c v switch

nonstandard voltmeter

given voltmeter

given circuit