Be8161-basic Electrical Electronics And Instrumentation Engineering Lab Manual 1ct6s

VALLIAMMAI ENGINEERING COLLEGE SRM NAGAR, KATTANKULATHUR – 603203

DEPARTMENT OF MECHANICAL ENGINEERING

BE8161-BASIC ELECTRICAL, ELECTRONICS AND INSTRUMENTATION ENGINEERING LABORATORY

LABORATORY MANUAL

II Semester – Mechanical Engineering (REGULATION 2017)

Prepared by, Mr.P.Tamilmani, AP (S.G)/EIE, Mr.K.R.Ganesh, AP(OG)/EIE, Ms.K.Rathna Priya, AP (OG)/EIE, Ms.Z.Jenifer, AP (OG)/EIE, Dr.R.Umamaheswari, AP (OG)/EIE, Ms.M.Ramya Princess, AP (OG)/EIE.

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SYLLABUS BE8261

BASIC ELECTRICAL, ELECTRONICS AND INSTRUMENTATION ENGINEERING LABORATORY

LTPC0042

LIST OF EXPERIMENTS .

1. Load test on separately excited DC generator 2. Load test on Single phase Transformer 3. Load test on Induction motor 4. Verification of Circuit Laws 5. Verification of Circuit Theorems 6. Measurement of three phase power 7. Load test on DC shunt motor. 8. Diode based application circuits 9. Transistor based application circuits 10. Study of CRO and measurement of AC signals 11. Characteristics of LVDT 12. Calibration of Rotameter 13. RTD and Thermistor

[Minimum of 10 Experiments to be carried out]

TOTAL: 60 PERIODS

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LABORATORY REQUIREMENTS FOR BATCH OF 30 STUDENTS

1. Regulated Power Supply: 0 – 15 V D.C - 10 Nos / Distributed Power Source. 2. Function Generator (1 MHz) - 10 Nos. 3. Single Phase Energy Meter - 1 No. 4. Oscilloscope (20 MHz)-10 Nos. 5. Digital Storage Oscilloscope (20 MHz) – 1 No. 6. AC/DC - Voltmeters (10 Nos.), Ammeters (10 Nos.) and Multi-meters (10 Nos.) 7. Single Phase Wattmeter – 3 Nos. 8. DC Motor Generator set-2 Nos 9. DC Shunt Motor- 2 Nos. 10. Single Phase Transformer-2 Nos. 11. Single Phase Induction Motor-2 Nos. 12. Circuit Connection Boards - 10 Nos. (Necessary Resistors, Inductors, Capacitors of various quantities (1 Watt to 10 Watt).

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BE8261

BASIC ELECTRICAL, ELECTRONICS AND INSTRUMENTATION

LABORATORY

Cycle – 1 1. Load test on separately excited DC generator 2. Load test on DC shunt motor 3. Study of CRO and measurement of AC signals 4. Diode based application circuits 5. Verification of Circuit Laws 6. Verification of Circuit Theorems 7. Transistor based application circuits

Cycle – 2 1. Load test on Single phase Transformer 2. Load test on Induction motor 3. Measurement of three phase power 4. Characteristics of LVDT 5. Calibration of Rotameter 6. RTD and Thermistor

ADDITIONAL EXPERIMENT

1. Open circuit and Short circuit tests on Single- phase transformer

4

Ex. No: 1.

LOAD TEST ON SEPARATELY EXCITIED DC GENERATOR

Date:

Aim:

To determine load characteristics of the given DC separately excited generator.

Apparatus required:

Sl.No.

Name

Range

Type

Quantity

1

Voltmeter

(0-300V)

MC

1

2

Ammeter

(0-10A)

MC

1

(0-2A)

MC

1

3

Rheostat

300Ω/1.4 A

Wire wound

2

4

Tachometer

(0-1500) rpm

Analog/Digital

1

5

Connecting wires

Required

Formula: ∆ E g

– Where, Rc – Critical resistance

I n

cremental generated EMF (measured from the linear portion OCC)

on the

∆If – Incremental field current (measured from the linear portion on the OCC).

5

Circuit Diagram:

6

Procedure:

1. 2. 3. 4.

Connections are given as per the circuit diagram. Observing the precautions the motor side DPST switch is closed. The motor is started with the help of three- point DC starter slowly. The speed is measured with the help of a hand tachometer.

5. If the speed is below the rated value, then it is brought to the rated value by adjusting the field rheostat. 6. With DPST switch on the generator field side open, the voltmeter reading is noted down. (This is the residual voltage at the rated speed at which the motor-generator set is running now.) 7. The DPST switch on the generator field side is closed. 8. By adjusting the potentiometer on the generator field side suitably for various increasing field currents, note down the terminal voltages till around 125% of the rated voltage. The speed is maintained constant throughout this process. 9. The generator terminal voltage is minimized to zero. 10. The speed is brought down to minimum value and the motor is switched off with the help of DPST switch. (Note the starter holding coil releasing the handle else bring it back to start position)

Tabulation: Speed

= _________rpm

Residual voltage

= ________ Volts

If (amps) S. No.

Eg (volts)

Model graph:

7

Eg ∆Eg

∆If

If

Load Characteristics:

Precaution:

1. The field rheostat on the motor side must be kept at minimum resistance position at the time of starting. 2. The field potentiometer on the generator side must be kept at minimum potential position at the time of starting. 3. DPST switches must be kept open at the time of power on. 4. There should be no load at the time of starting. Procedure:

1. 2. 3. 4.

Connections are given as per the circuit diagram. Observing the precautions the motor side DPST switch is closed. The motor is started with the help of three- point DC starter slowly. The speed is measured with the help of a hand tachometer.

5. If the speed is below the rated value, then it is brought to the rated value by adjusting the field rheostat. 6. By adjusting the potentiometer on the generator side the generator terminal voltage is brought to the rated value. 7. Load side DPST switch is closed. 8. The load is applied gradually. For various load currents voltmeter and ammeter readings are noted down till full current of the generator. (Avoid sustained overload.) 9. The load is brought back to initial no load position. 10. DPST switch on the load side is opened. 11. Generator field circuit potentiometer is brought to minimum potential position. 12. DPST switch on the generator field side is opened.

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13.

The speed is brought down to minimum value and the motor is switched off with the help of DPST switch. (Note the starter holding coil releasing the handle else bring it back to start position)

14. Disconnect and return the apparatus.

Tabulation: Ra = _________ Ohms

IL = Ia

V

IaRa

Eg = V + IaRa

(Amps)

(Volts)

(Volts)

(Volts)

S. No.

Model graph:

V

Eg Vs Ia

& Eg V Vs IL

I a & IL

Viva Questions:

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1. What is Internal Characteristics? 2. What is External Characteristics? 3. What is the difference between the generating voltage and terminal voltage? 4. Write the derivation for generating voltage? 5. How the armature resistance are determined? Result:

1. The Open Circuit Characteristics of the given separately excited DC generator was obtained and the Critical resistance at rated speed is found to be ______ohms. 2. The Load Characteristics (Internal & External) of the given separately excited DC generator was obtained.

Ex. No: 2.

LOAD TEST ON DC SHUNT MOTOR

Date:

10

Aim:







To determine the efficiency of D.C shunt motor. To obtain the performance characteristics of shunt motor.





Apparatus required:

Sl. No.

Name of the apparatus

Range

Type

Quantity

1.

Ammeter

(0 - 2A)

MC

1

2.

Ammeter

(0 - 10A)

MC

1

3.

Voltmeter

(0 - 300V)

MC

1

Wire wound

1

Digital

1

400 Ω/1.1A, 4.

Rheostat

5.

Tachometer

(0 -9999 rpm)

Precautions:

At the time of switching on and switching off the supply,



 

The field rheostat should be at the minimum resistance position. There should not be any load on the motor.





Range fixing:

The line Current of the shunt motor is IL = _______ A The current drawn by the shunt motor on load is 120% of full load current. The range of ammeter AL is (0 - ) A

The rated field current is _____ A Field circuit rheostat rating is _____ ; ____ A (the current rating should be slightly higher than the rated current) Rated voltage of motor V = _______ Volts The range of voltmeter V is (0 - ) Volts

Circuit Diagram for Load Test on D.C. Shunt Motor:

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Motor Specifications Voltage Line Current Speed Capacity

Tabulation:

S.No.

V

I

Spring Balance

Speed Torque

Output

Input

Efficiency η

(Kg) (Volts)

(Amps) F1

F2

F1~ F2

N

T

Power

Power

(rpm)

(Nm)

Po

Pi

%

(Watts)

(Watts)

Radius of brake drum, r = __________ mts.

MODEL GRAPH:

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Viva questions:

1. Why a DC shunt motor is called a constant Speed motor? 2. State few applications of DC shunt series motor. 3. What is the role of commutator in a DC motor? 4. What is the effect of armature reaction on the performance of DC motor? 5. What happen when the field circuit gets opened when a DC shunt motor is running? 6. How to reverse the direction of rotation of DC motor? 7. Define torque. 8. What is meant by efficiency? 9. At the starting of motor the field rheostat must be in minimum position. Why? 10. If there is open circuit in the field circuit. What happen? 11. Name the different types of starters for DC motors Result: Thus the performance characteristics of the DC shunt motor were drawn.

EXPT 3

STUDY OF CRO and Measurement of AC Signals

Date:

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AIM: The aim of the experiment is to understand the operation of cathode ray oscilloscope (CRO) and to become familiar with its usage, also to perform an experiment using function generator to measure amplitude, time period, frequency & power factor of the time varying signals using a calibrated cathode ray oscilloscope.

APPARATUS REQUIRED:

Sl.No

Name of the Components/Equipment

Qty

1.

CRO

1

2.

Function generator

2

3.

Probes

2

THEORY: The cathode ray oscilloscope (CRO) provides a visual presentation of any waveform applied to the input terminal. The oscilloscope consists of the following major subsystems.

    



Cathode ray tube (CRT)



Vertical amplifier



Horizontal amplifier



Sweep Generator



Trigger circuit



Associated power supply

It can be employed to measure quantities such as peak voltage, frequency, phase difference, pulse width, delay time, rise time, and fall time.

CATHODE RAY TUBE:

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The CRT is the heart of the CRO providing visual display of an input signal waveform. A CRT contains four basic parts:





An electron gun to provide a stream of electrons.



Focusing and accelerating elements to produce a well define beam of electrons.

 

Horizontal and vertical deflecting plates to control the path of the electron beam.

 

An evacuated glass envelope with a phosphorescent which glows visibly when struck by electron beam.

A Cathode containing an oxide coating is heated indirectly by a filament resulting in the release of electrons from the cathode surface. The control grid which has a negative potential, controls the electron flow from the cathode and thus control the number of electron directed to the screen. Once the electron es the control grid, they are focused into a tight beam and accelerated to a higher velocity by focusing and accelerating anodes. The high velocity and well defined electron beam then ed through two sets of deflection plates. The First set of plates is oriented to deflect the electron beam vertically. The angle of the vertical deflection is determined by the voltage polarity applied to the deflection plates. The electron beam is also being deflected horizontally by a voltage applied to the horizontal deflection plates. The tube sensitivity to deflecting voltages can be expressed in two ways that are deflection factor and deflection sensitivity. The deflected beam is then further accelerated by very high voltages applied to the tube with the beam finally striking a phosphorescent material on the inside face of the tube. The phosphor glows when struck by the energetic electrons.

CONTROL GRID: Regulates the number of electrons that reach the anode and hence the brightness of the spot on the screen.

FOCUSING ANODE: Ensures that electrons leaving the cathode in slightly different directions are focused down to a narrow beam and all arrive at the same spot on the screen.

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ELECTOR GUN: Cathode, control grid, focusing anode, and accelerating anode. DEFLECTING PLATES: Electric fields between the first pair of plates deflect the electrons horizontally and an electric field between the second pair deflects them vertically. If no deflecting fields are present, the electrons travel in a straight line from the hole in the accelerating anode to the center of the screen, where they produce a bright spot. In general purpose oscilloscope, amplifier circuits are needed to increase the input signal to the voltage level required to operate the tube because the signals measured using CRO are typically small. There are amplifier sections for both vertical and horizontal deflection of the beam. VERTICAL AMPLIFIER: Amplify the signal at its input prior to the signal being applied to the vertical deflection plates. HORIZONTAL AMPLIFIER: Amplify the signal at its input prior to the signal being applied to the horizontal deflection plates. SWEEP GENERATOR: Develop a voltage at the horizontal deflection plate that increases linearly with time. OPERATION: The four main parts of the oscilloscope CRT are designed to create and direct an electron beam to a screen to form an image. The oscilloscope links to a circuit that directly connects to the vertical deflection plates while the horizontal plates have linearly increasing charge to form a plot of the circuit voltage over time. In an operating cycle, the heater gives electrons in the cathode enough energy to escape. The electrons are attracted to the accelerating anode and pulled through a control grid that regulates the number of electrons in the beam, a focusing anode that controls the width of the beam, and the accelerating anode

itself. The vertical and horizontal deflection plates create electric field that bend the beam of electrons. The electrons finally hit the fluorescent screen which absorbs the energy from the electron beam and emits it in the form of light to display an image at the end of the glass tube.

PRECAUTIONS:

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1. Do not leave a „bright spot‟ on the screen for any length of time. 2. Do not apply signals that exceed the scopes voltage rating. 3. Do not try make accurate measurements on signals whose frequency is outside the scope‟s frequency specifications. 4. Be aware that the scope‟s input circuitry can cause loading effects on the circuitry under test-use correct probe for the work. PRODEDURE:

1. Measurement of Voltage Using CRO : A voltage can be measured by noting the Y deflection produced by the voltage; using this deflection in conjunction with the Y-gain setting, the voltage can be calculated as follows : V = ( no. of boxes in cm. ) x ( selected Volts/cm scale ) 2 .Measurement of Current and Resistance Using a CRO: Using the general method, a correctly calibrated CRO can be used in conjunction with a known value of resistance R to determine the current I flowing through the resistor. 3 Measurement of Frequency Using a CRO: A simple method of determining the frequency of a signal is to estimate its periodic time from the trace on the screen of a CRT. However this method has limited accuracy, and should only be used where other methods are not available. To calculate the frequency of the observed signal, one has to measure the period, i.e. the time taken for 1 complete cycle, using the calibrated sweep scale. The period could be calculated by T = (no. of squares in cm) x (selected Time/cm scale) Once the period T is known, the frequency is given by f (Hz)= 1/T(sec) 4. Measurement of Phase: The calibrated time scales can be used to calculate the phase shift between two sinusoidal signals of the same frequency. If a dual trace or beam CRO is available to display the two signals simultaneously (one of the signals is used for synchronization), both of the signals will appear in proper time perspective and the amount of time difference between the waveforms can be measured. This, in turn can be utilized to calculate the phase angle θ, between the two signals.

Tabulation:

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Sl.No

Type of

Time

wave

period (T)

Amplitude

Theoretical

Practical

Frequency

Frequency

1.

2.

3.

Sl

Waveform Peak volt

Amplitude in volts

Time

Frequency

Peak-peak

Period

in Hz

RMS volt

in seconds 1

Sine

2

Triangular

3

Square

VIVA QUESTIONS: 1. What is a CRO? 2. How can we measure the voltage using a CRO? 3. Explain the different parts of the CRO 4. Explain the operation of a CRO.

RESULT:

Thus the Analog and digital oscilloscopes were studied and measurement of sinusoidal voltage, frequency and power factor was done. EXPT 4

DIODE BASED APPLICATION CIRCUITS

Date:

4(a) MEASUREMENT OF RIPPLE FACTOR FOR HALF WAVE RECTIFIERS

AIM: To study the ripple factor of a half wave rectifier .

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APPARATUS REQUIRED:

SL.NO. NAME OF THE

RANGE

QUANTITY

EQUIPMENT 1.

Transformer

2.

Capacitor

12v-0v-12v

1 2

0.1 µF 3.

Resistor

4.

PN junction diode

470Ω

1 2

IN 4007 5.

Bread Board

-

1

6.

CRO

FORMULA:

Ripple Factor, = (Vrms / Vdc)2- 1 Where, Vrms = The rms value of the a.c component of the output voltage Vdc = The average or d.c value of the output voltage.

HALF WAVE RECTIFIER: Vdc = Vm/2π Vrms = Vm/2

1

Theory: A rectifier is defined as a electronic device used for converting AC voltage into unidirectional voltage. A rectifier utilizes unidirectional conduction devices like Vacuum diode or PN junction diode.

Half wave rectifier: It converts an ac voltage into a pulsating DC voltage using only one half of the applied ac voltage. The rectifying diode conducts during one half of the ac cycle. During

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positive half cycle of the input signal the anode of diode becomes positive with respect to cathode and hence the diode conducts. For an ideal diode the forward voltage drop is zero so the whole input voltage appears across the load. During negative half of the input signal the anode of the diode becomes negative with respect to cathode and hence the diode does not conduct. For an ideal diode the impedance offered by the diode is unity so the whole input voltage drop across diode. Hence voltage drop across RL is zero.

CIRCUIT DIAGRAM Half Wave Rectifier

MODEL GRAPH:

20

TABULATION: TYPE OF RECTIFIER

Vm

Time

Ripple factor

Period

Half Wave Rectifier

PROCEDURE: 1. Connect the circuit as per the circuit diagram. 2. Connect the CRO across the load. 3. From the waveform in the CRO screen, note down the amplitude and frequency along with multiplication factor.

4. Calculate the ripple factor.

VIVA QUESTIONS: 1. Define Rectifier ? 2. What is Half-Wave Rectifier ? 3. Define Ripple Factor ? 4. What type of output we get from HW Rectifier ? 5. What is the value of Ripple factor for HW Rectifier ? 6. What is the formulae for Vrms for HW Rectifier ?

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7. What is the formulae for Vdc for HW Rectifier ?

RESULT: Thus the input & output waveforms are drawn for half wave rectifiers and ripple factor calculated.

Ex. No.4 (b) MEASUREMENT OF RIPPLE FACTOR FOR FULL WAVE RECTIFIERS

AIM:

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To study the ripple factor and regulation characteristics of a full wave rectifier.

EQUIPMENTS REQUIRED:

SL.NO. NAME OF THE

RANGE

QUANTITY

EQUIPMENT 1.

Transformer

2.

Capacitor

12v-0v-12v

1 2

0.1 µF 3.

Resistor

4.

PN junction diode

470Ω

1 2

IN 4007 5.

Bread Board

-

1

6.

CRO

FORMULA USED: Ripple Factor, = (Vrms / Vdc)2- 1 Where, Vrms = The rms value of the a.c component of the output voltage Vdc = The average or d.c value of the output voltage.

FULL WAVE RECTIFIER: Vdc = 2 Vm/π

1

Vrms = Vm/ 2

Theory: A rectifier is defined as a electronic device used for converting AC voltage into unidirectional voltage. A rectifier utilizes unidirectional conduction devices like Vacuum diode or PN junction diode. Full wave rectifier:

23

It converts an AC voltage in to a pulsating DC voltage using both half cycles of the applied AC voltage. It uses two diodes of which one conducts during positive half cycle while the other conducts during negative half cycle. During positive half cycle of the input signal anode of the diode D1 becomes positive with respect to cathode and at the same time anode of the diode becomes negative. Hence D1 conducts and D2 will not conduct during positive half cycle. During negative half of the input anode of the diode D1 becomes negative and anode of diode D2 becomes positive. Hence D1 does not conduct and D2 will conduct. The load current flows through D2 and voltage drop across RL will be equal to the input voltage.

PROCEDURE: 1. Connect the circuit as per the circuit diagram. 2. Connect the CRO across the load. 3. From the waveform in the CRO screen, note down the amplitude and frequency along with multiplication factor. 4. Calculate the ripple factor.

CIRCUIT DIAGRAM FULL WAVE RECTIFIER

MODEL

GRAPH

TABULATION: TYPE OF

Vm

RECTIFIER

Time

Ripple

Period

factor

Full Wave Rectifier

VIVA QUESTIONS: 1. Define Full wave rectifier? 2. What is the formulae for Vdc for FW Rectifier? 3. What is the formulae for Vrms for FW Rectifier 4. What type of output we get from FW Rectifier?

5. What is the value of Ripple factor for FW Rectifier?

RESULT: Thus the input & output waveforms are drawn for full wave rectifiers and ripple factor calculated

EXP.NO:5 EXPERIMENTAL VERIFICATION OF ELECTRICAL CIRCUIT PROBLEMS USING KIRCHHOFF’S VOLTAGE AND CURRENT LAWS DATE:

25

AIM:

To (i) Kirchhoff‟s current law (ii) Kirchhoff‟s voltage law

APPARATUS REQUIRED:

Sl.No

Name of the apparatus

1

RPS

2

Resistor

3

Ammeter

4

Voltmeter

5

Bread board

6

Connecting wires

Range

Type

Quantity

KIRCHHOFF’S CURRENT LAW: THEORY:

The law states, “The sum of the currents entering a node is equal to sum of the currents leaving the same node”. Alternatively, the algebraic sum of currents at a node is equal to zero. The term node means a common point where the different elements are connected. Assume negative sign for leaving current and positive sign for entering current.

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CIRCUIT DIAGRAM FOR KIRCHHOFF’S CURRENT LAW

TABULATION:

Sl.No

V

I1

I2

I3

I1 = I2 + I3

(Volts)

(mA)

(mA)

(mA)

( mA)

THEORETICAL CALCULATION

27

V

I1

I2

I3

I1 = I2 + I3

(Volts)

(mA)

(mA)

(mA)

( mA)

S.No.

MODEL CALCULATION:

PROCEDURE: 1. Connect the circuit as per the circuit diagram.

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2. Switch on the supply. 3. Set different values of voltages in the RPS. 4. Measure the corresponding values of branch currents I1, I2 and I3. 5. Enter the readings in the tabular column. 6. Find the theoretical values and compare with the practical values

FORMULA:

∑ Currents entering a node = ∑ Currents leaving the node I1 = I2 + I3

CIRCUIT DIAGRAM FOR KIRCHHOFF’S VOLTAGE LAW:

OBSERVATION TABLE:

S.No.

V

V1

V2

V3

V =V1+ V2

29

Volts Volts Volts Volts

+V3 Volts

KIRCHHOFF’S VOLTAGE LAW: THEORY: The law states, “The algebraic sum of the voltages in a closed circuit/mesh is zero”. The voltage rise is taken as positive and the voltage drop is taken as negative.

PROCEDURE:

1. Connect the circuit as per the circuit diagram. 2. Switch on the supply. 3. Set different values of voltages in the RPS. 4. Measure the corresponding values of voltages (V1, V2 and V3) across resistors R1, R2 and R3 respectively. 5. Enter the readings in the tabular column.

6. Find the theoretical values and compare with the practical values.

FORMULA:

∑ Voltages in a closed loop = 0 V-V1-V2-V3 = 0

30

THEORETICAL CALCULATION:

S.No.

V

V1

V2

V2

Volts

Volts

Volts

Volts

MODEL CALCULATION:

V =V1+ V2 + V3 Volts

VIVA QUESTIONS:

1. State Kirchhoff‟s Voltage Law. 2. State Kirchhoff‟s Current Law. 3. What is current division rule? 31

4. What is voltage division rule? 5. Give the equivalent resistance when „n‟ number of resistances is connected in series. 6. Give the equivalent resistance when „n‟ number of resistances is connected in parallel

RESULT:

Thus the Kirchhoff‟s Current and Voltage laws are verified.

EXPT NO: 6

VERIFICATION OF CIRCUIT THEOREMS

DATE: EXP.NO:6(a) SIMULATION AND EXPERIMENTAL VERIFICATION OF ELECTRICAL CIRCUIT PROBLEMS USING THEVENIN’S THEOREM AIM: To Thevenin‟s theorem.

32

APPARATUS REQUIRED: Sl.No no

Name of the Components /

Type/Range

Quantity required

Equipment 1

Resistor

2

Dc power supply

3

Voltmeter

4

Ammeter

5

Wires

6

Bread board

THEVENIN’S THEOREM: STATEMENT: Any two-terminal linear network, composed of voltage sources, current sources, and resistors, can be replaced by an equivalent two-terminal network consisting of an independent voltage source in series with a resistor. The value of voltage source is equivalent to the open circuit voltage (Vth) across two terminals of the network and the resistance is equal to the equivalent resistance (Rth) measured between the terminals with all energy sources replaced by their internal resistances.

Rth

Circuit

Vth

THEVENIN’S EQUIVALENT CIRCUIT

33

CIRCUIT DIAGRAM FOR THEVENIN’S THEOREM:

TO FIND LOAD CURRENT:

TO FIND Vth:

34

TO FIND Rth:

PROCEDURE: 1. Give connections as per the circuit diagram.

35

2. Measure the current through RL in the ammeter. 3. Open circuit the output terminals by disconnecting load resistance RL. 4. Connect a voltmeter across AB and measure the open circuit voltage Vth. 5. To find Rth, replace the voltage source by short circuit. 6. Give connections as per the Thevenin‟s Equivalent circuit. 7.

Measure the current through load resistance in Thevenin‟s Equivalent circuit.

8. Thevenin‟s theorem by comparing the measured currents in Thevenin‟s Equivalent circuit with the values calculated theoretically. OBSERVATION TABLE:

Vth

Current through Load Rth

(Volts)

Resistance (Ω)

S.

IL(mA) No Vdc Practical Value

Theoretical Practical Value

Value

Theoretical

Practical

Theoretical

Value

Value

Value

VIVA QUESTIONS: 1. What is meant by a linear network? 2. State Thevenin‟s Theorem.

36

3. How do you calculate thevenin‟s resistance? RESULT: Thus the Thevenin‟s theorem was verified.

EXPT NO 6(b) SIMULATION AND EXPERIMENTAL VERIFICATION OF ELECTRICAL CIRCUIT PROBLEMS USING NORTON’S THEOREM AIM:

37

To Norton‟s theorem.

APPARATUS REQUIRED:

Sl.No no

Name of the Components /

Type/Range

Quantity required

Equipment 1

Resistor

2

Dc power supply

3

Voltmeter

4

Ammeter

5

Wires

6

Bread board

NORTON’S THEOREM STATEMENT: Any two-terminal linear network, composed of voltage sources, current sources, and resistors, can be replaced by an equivalent two-terminal network consisting of an independent current source in parallel with a resistor. The value of the current source is the short circuit current (IN) between the two terminals of the network and the resistance is equal to the equivalent resistance (RN) measured between the terminals with all energy sources replaced by their internal resistances.

NORTON’S EQUIVALENT CIRCUIT:

38

Circuit IN

CIRCUIT DIAGRAM FOR NORTON’STHEOREM:

RN

TO FIND NORTON’S CURRENT:

39

TO FIND NORTON’S RESISTANCE:

PROCEDURE:

1. Give connections as per the circuit diagram.

40

2. Measure the current through RL in ammeter. 3. Short circuit A and B through an ammeter. 4. Measure the Norton current in the ammeter. 5. Find out the Norton‟s Resistance viewed from the output terminals. 6. Give connections as per the Norton‟s Equivalent circuit. 7. Measure the current through RL. 8. Norton‟s theorem by comparing currents in RL directly and that obtained with the equivalent circuit.

VIVA QUESTIONS: 1. How do you calculate Norton‟s resistance? 2. State Norton‟s Theorem. 3. Give the usefulness of Norton‟s theorems.

RESULT:

Thus the Norton‟s theorem was verified.

EXP.NO:6(c) SIMULATION AND EXPERIMENTAL VERIFICATION OF ELECTRICAL CIRCUIT PROBLEMS USING SUPERPOSITION THEOREM

41

AIM: To superposition theorem. APPARATUS REQUIRED:

Sl.No

Name of the Components / Type/Range Quantity required

Equipment 1

Resistor

2

Dc power supply

3

Voltmeter

4

Ammeter

5

Wires

6

Bread board

SUPERPOSITION THEOREM: STATEMENT: In any linear, bilateral network energized by two or more sources, the total response is equal to the algebraic sum of the responses caused by individual sources acting alone while the other sources are replaced by their internal resistances. To replace the other sources by their internal resistances, the voltage sources are short- circuited and the current sources open- circuited.

CIRCUIT DIAGRAM FOR SUPERPOSITION THEOREM:

42

CIRCUIT DIAGRAM WITH V1 ACTING INDEPENDENTLY:

CIRCUIT DIAGRAM WITH V2 ACTING INDEPENDENTLY:

43

PROCEDURE :

1. Connections are made as per the circuit diagram given in Fig. 1. 2. Switch on the supply. 3. Note the readings of three Ammeters. 4. One of the voltage source V1 is connected and the other voltage source V2 is short circuited as given in Fig.2. 5. Note the three ammeter readings. 6. Now short circuit the voltage source V1 and connect the voltage source V2 as given in the circuit diagram of Fig. 3. 7. Note the three ammeter readings.

8. Algebraically add the currents in steps (5) and (7) above to compare with the current in step (3) to the theorem. 9. with theoretical values. FORMULAE :

I3’ + I3’’ = I3

OBSERVATION TABLE: Experimental Values:

Theoretical Values:

44

V1

V2

I3

(Volts)

(Volts)

(mA)

V1

V2

I3

(Volts)

(Volts)

(mA)

VIVA QUESTIONS: 1. State Superposition Theorem. 2. What is meant by a linear system? 3. Give the usefulness of Superposition Theorem. 4. How will you apply Superposition Theorem to a linear circuit containing both dependent and independent sources? 5. State the limitations of Superposition theorem.

RESULT: Thus the Superposition theorem was verified.

EXP.NO:6(D) SIMULATION AND EXPERIMENTAL VERIFICATION OF ELECTRICAL CIRCUIT PROBLEMS USING MAXIMUM POWER TRANSFER THEOREM

45

AIM: To maximum power transfer theorem. APPARATUS REQUIRED:

Sl.No

Name of the Components / Type/Range Quantity required

Equipment 1

Resistor

2

Dc power supply

3

Voltmeter

4

Ammeter

5

Wires

6

Bread board

MAXIMUM POWER TRANSFER THEOREM:

THEORY:

The Maximum Power Transfer Theorem states that maximum power is delivered from a source to a load when the load resistance is equal to source resistance. CIRCUIT DIAGRAM FOR MAXIMUM POWER TRANSFER THEOREM:

OBSERVATION TABLE:

Sl.No.

RL (kΩ)

IL (mA) Practical

Theoretical

P = I2RL (mW) Practical Theoretical

46

Value

MODEL GRAPH:

MODEL CALCULATION:

Value

Value

Value

PROCEDURE:

1. Find the Load current for the minimum position of the Rheostat theoretically. 2. Select the ammeter Range. 3. Give connections as per the circuit diagram. 47

4. Measure the load current by gradually increasing RL . 5. Enter the readings in the tabular column. 6. Calculate the power delivered in RL. 7. Plot the curve between RL and power. 8. Check whether the power is maximum at a value of load resistance that equals source resistance. 9. the maximum power transfer theorem.

VIVA QUESTIONS:

1. Define Power. What is the unit of Power? 2. State Maximum Power Transfer Theorem

RESULT:

Thus the Maximum power transfer theorem was verified.

EX. NO. 7

TRANSISTOR BASED CIRCUITS

Date: EXPT NO. 7(A)

COMMON EMITTER AMPLIFIER

AIM:

48

To observe input-output waveforms of common emitter (CE) amplifier. To measure gain of amplifier at different frequencies and plot frequency response.

Apparatus Required:

Sl.No Name of the components

Range

Quantity

Theory:

Common emitter amplifier is used to amplify weak signal. It utilizes energy from DC power supply to amplify input AC signal. Biasing of transistor is done to tie Q point at the middle of the load line. In the circuit shown, voltage divider bias is formed using resistors 10K and 2.2K. During positive cycle, forward bias of base-emitter junction increases and base current increases. Q point moves in upward direction on load line and collector current increases β times than base current. (β is current gain). Collector resistor drop IcRc increases due to increase in collector current Ic. This will reduce collector voltage. Thus during positive input cycle, we get negative output cycle. When input is negative cycle, forward bias of base emitter junction and base current will reduce. Collector current reduces (Q-point moves downside). Due to decrease in collector current, collector resistance voltage drop IcRc reduces and collector voltage increases. Change in collector voltage is much higher than applied base voltage because less base current variation causes large collector current variation due to current gain B. This large collector current further multiplied by collector resistance Rc which provides large voltage output. Thus CE amplifier provides voltage gain and amplifies the input signal. Without emitter resistance gain of amplifier is highest but it is not stable. Emitter resistance is used to provide stability. To compensate effect of emitter resistance emitter by capacitor is used which provides AC ground to the emitter. This will increase gain of amplifier. CE amplifier does not provide constant voltage gain at all frequencies. Due to emitter by and coupling capacitors reduces gain of amplifier at low frequency. Reactance of capacitor is high at low frequency, hence emitter by capacitor does not provide perfect AC ground (Emitter because of high reactance at low frequencies.

Gain of CE amplifier also reduces at very high frequency because of stray capacitances. Audio frequency transistors like AC127, AC128 works for audio frequency range. It does not provide large voltage gain for frequency greater than 20 KHz. Medium frequency transistors are BC147/BC148/BC547/BC548 provides voltage gain up to 500 KHz. High frequency transistors like BF194/BF594/BF200 provides gain at radio frequencies in the MHz range. If we apply large signal at the input of CE amplifier, transistor driven into saturation region during positive peak and cut-off region during negative peak (Q point

49

reaches to saturation and cut-off points). Due to this clipping occurs in amplified signal. So we have to apply small signal at the input and ensure that transistor operates in active region. Circuit Diagram:

Tabulation: Input Voltage:

Sl.

Frequency At the

Ouput

No

input

voltage Vo

Gain A=Vo/Vin

Gain in dB=20log(A)

50 Model Calculation:

Procedure:

1. 2. 3. 4. 5. 6. 7.

Give the connection as per the circuit diagram Set input voltage 10 mV and frequency 100 Hz. Connect CRO at the output of the amplifier circuit. Observe amplified signal and measure output voltage Increase frequency from the function generator and repeat above step Note down readings of output voltage in the observation table for frequency range from 100 Hz to 10 MHz

8. Calculate voltage gain for different frequencies and gain in dB. Plot frequency response.

Result:

Thus the input/output waveform for common emitter amplifier were observed and frequency response was plotted.

EX.NO: 7(B)

CHARACTERISTICS OF CE CONFIGURATION

Aim: To obtain common emitter characteristics of NPN transistor Components required:

S.No Components required

Range

Quantity

51

Theory: Transistor is three terminal active device having terminals collector, base and emitter. Transistor is widely used in amplifier, oscillator, electronic switch and so many other electronics circuits for variety of applications. To understand operation of the transistor, we use three configurations common emitter, common base and common collector. In this practical, we will understand common emitter configuration. As the name suggest, emitter is common between input and output. Input is applied to base and output is taken from collector. We will obtain input characteristics and output characteristics of common emitter (CE) configuration. We will connect variable DC power supply at VBB and VCC to obtain characteristics. Input voltage in CE configuration is base emitter voltage VBE and input current is base current IB. Output voltage in CE configuration is collector to emitter voltage VCE and output current is collector current IC. We will use multi-meter to measure these voltages and currents for different characteristics. Collector to emitter junction is reverse biased and base to emitter junction is forward biased. The CE configuration is widely used in amplifier circuits because it provides voltage gain as well as current gain. In CB configuration current gain is less than unity. In CC configuration voltage gain is less than unity. Input resistance of CE configuration is less than CC configuration and more than CB configuration. Output resistance of CE configuration is more than CC configuration and less than CB configuration.

Circuit diagram:

52

Tabulation: Input characteristics

S.No

VCC=0V VBE

VCC=+5V IB

Tabulation: Output characteristics

VBE

VCC=+10V IB

VBE

IB

S.No

IB=0µA VCE

IB =+50µA IC

VCE

IB =+100µA IC

VCE

IC

Model Calculation:

53

Experiment Procedure:

Input Characteristics: 1. Connect circuit as shown in the circuit diagram for input characteristics 2. Connect variable power supply 0-30V at base circuit and collector circuit. 3. Keep VCC fix at 0V (Or do not connect VCC) 4. Increase VBB from 0V to 20V, note down readings of base current IB and base to emitter voltage VBE in the observation table. 5. Repeat above procedure for VCC = +5V and VCC = +10V 6. Draw input characteristics curve. Plot VBE on X axis and IB on Y axis. Output characteristics: 1. 2. 3. 4.

Connect circuit as shown in the circuit diagram for output characteristics Connect variable power supply 0-30V at base circuit and collector circuit. Keep base current fix (Initially 0) Increase VCC from 0V to 30V, note down readings of collector current IC and collector to emitter voltage VCE in the observation table.

5. Repeat above procedure for base currents Ib = 5μA, 50 μA, 100 μA. Increase base current by increasing VBB. 6. Draw output characteristics curve. Plot VCE on X axis and IC on Y axis.

Result:

Thus to obtain common emitter characteristics of NPN transistor

EX.NO : 8

LOAD TEST ON SINGLE PHASE TRANSFORMER

Date: Aim:

54









To determine the efficiency

To find the variation of secondary terminal voltage with respect to the load current.



Apparatus required:

S.No.

Item

Type

Range

Quantity

Precaution:



 

The Variac should be kept  in minimum position while switching on and switching off the supply side DPSTS. At the time of switching on the supply there should not be any load connected.



Range fixing: Rated primary current, I1 

Rated capacity in VA Pr imary voltage, V1

Rated secondary current, I 2 

Rated capacity in VA Secondary voltage, V2

The load used is resistive in nature. The range of Ap, Vp, Wp are …………A, ……………V, …………W respectively. The range of As, Vs, Ws are ……………A, …………….V, …………..W respectively.

Procedure:   

  

Excite the transformer to its rated voltage on no load. Observe the meter readings at no load.





Gradually load the transformer and note the meter readings for each loading.





Load the transformer to its rated capacity i.e. till it draws rated current from the supply.

Note that applied voltage to the primary side should be kept at its rated voltage on loading.

Formulae Used: Output power =

WS

Input Power =

WP

55

% =

W S

 100

WP

% Regulation =

VS 0  VS

 100 (where VS0 – no load secondary rated terminal voltage)

V

S0

Circuit Diagram for Load Test on Single Phase Transformer:

Variac Specifications O/P Voltage Current Rating

Transformer Specifications

Capacity Py. Voltage Sy. Voltage

Observation: MF = Sl.No

VP

IP

(Volts) (Amps)

WP (Watts)

Observed

VS

MF = IS

Actual (Volts) (Amps)

WS (Watts)

Observed

Actual

%

%

Efficiency Regulation

Model Graphs:

56

Viva Questions:

1. Define Regulation of a Transformer. 2. What is the effect of load p.f on regulation of Transformer? 3. What is the condition for maximum efficiency? 4. Determine the percentage load at which maximum efficiency occurred for the given Single-phase transformer? 5. What is the effect of change in frequency on the efficiency of the transformer? 6. Why transformer rating is in KVA?

Result:

Thus the efficiency and regulation of a three phase transformer were calculated .

Ex.No : 9

LOAD TEST ON SINGLE PHASE INDUCTION MOTOR

Date:

57

AIM: To conduct the load test on the given single phase induction motor and to plot its performance characteristics.

NAME PLATE DETAILS:

FUSE RATING CALCULATION:

APPARATUS REQUIRED:

SL NO

NAME OF THE EQUIPMENTS/INSTRUMENTS

CIRCUIT DIAGRAM :

TYPE

RANGE QUANTITY

Model Graph:

58

PRECAUTIONS:

1. Before starting the motor, release the load completely. 2. Before providing a.c supply, the single phase variac must be in the minimum position. 3. Handle the tachometer carefully.

PROCEDURE:

1. Make the connections as per the circuit diagram. Release any load available on the motor. Switch ON the power supply by closing DPST switch. 2. Vary the single phase auto transformer for rated input voltage. 3. Initially when the motor is unloaded, note the readings of ammeter, voltmeter and wattmeter. Measure the speed using a tachometer at this no load condition. 4. Load the motor in gradual steps up to the rated current. At each step, note down all the above mentioned readings. 5. Add cooling water to the brake drum as and when required when the motor is loaded. 6. Release the load on the motor and bring the auto transformer to initial position. 7. Switch OFF the supply.

8. Measure the circumferential length of the brake drum and use the same for calculation of the radius „R‟ of the brake drum. CALCULATIONS:

1. Torque, T= 9.81 (S1 ~ S2) R

(Nm)

where R=(r + t /2) (m) R---effective radius of the brake drum (m) r--- Radius of the braked drum (m) t---thickness of the belt (m)

2. Output power, Po = 2πNT/60 (W)

59

where N- actual speed of the motor (rpm)

3. Input power Pi = W (W) where W- actual reading of the wattmeter reading (W)

4. % Slip S= (Ns-N)/Ns x 100 (%) Where Ns-Synchronous speed (rpm), N=1500 rpm.

14.

Power factor cosφ =Pi / (V * I) where V-line voltage (V) I-line current (A)

Efficiency %η = (Po/Pi) x 100 (%)

7. Multiplication Factor (MF) of the wattmeter:

MF= (Current Coil Rating * Pressure Coil Rating * Power Factor)/ Full Scale Deflection of the wattmeter

13. Ns = 120 * f/ P Where f is the frequency of the supply (or) stator frequency P is the no. of poles of the motor

TABULATION:

Sl.

VL

IL

Spee I/P

Spring

No.

(V)

(A)

d

reading

Power

(rp m)

Balance Torque (Nm)

(W) Ob s

Act

O/P Power (W)

S1

S2

S1~S2

%slip

%η

cosφ

MODEL CALCULATIONS:

60

Viva Question 8. What are the different types of single phase induction motors? 9. Explain why single phase induction motors are not self-starting? 10. Draw the phasor diagrams of Single phase induction motor indicating the starting winding and running winding current components. 11. Define slip. 12. List out the applications of Single Phase induction motors.

RESULT: Thus the load test is performed in single phase Induction Motor and performance characteristics are drawn.

61

EX. NO: 10 MEASUERMENT OF THREE PHASE POWER Date: AIM: To measure the three phase power using two wattmeter method and also find the power factor value.

APPARATUS REQUIRED:

S.No

Apparatus

Range

Quantity

1

Ammeter

(0-10A)MI

1

2

Voltmeter

(0-600V)MI

1

3

Wattmeter

600V,10A,UPF

2

4

Three phase Resistive load

-

1

5

Three phase autotransformer

-

1

6

Connecting wires

-

Few

FORMULA USED: Total Power W = W1+W2 watts Where, W1&W2 are Wattmeter Readings

Total Power W = √3 VLIL cosФ VL & IL are Load Voltage and Current THEORY: In 3Ф circuits whether the load is star connected or delta connected, total 3Ф power is given by √3 VLILcosФ. The Ф is the angle between Vph and I ph. The power is measured by using wattmeter‟s. Wattmeter is a device which gives power reading, when connected in 1Ф or 3Ф system, directly in watts. It consists of two coils 1. Current coil, 2.voltage coil (or) pressure coil. The current coils of the two wattmeter are connected in any two lines while the voltage coil of each wattmeter is connected between its own current coil terminal and the line without a current coil. For example, the current coils are inserted in the lines R and Y then

the pressure coils are connected between R B for one wattmeter and Y B for other wattmeter. The connections are same for star or delta connected load. In two wattmeter method, the algebraic sum of the two wattmeter reading gives the total power dissipated in the 3Ф circuit. If W1 &W2 are the two wattmeter readings then the total power W= W1+W2 in watts

62

TABULATION:

Load

Load

Supply

Wattmeter

Total Power Power Factor

PowerW =√3

Voltage Current

Total

Reading

W= W1+W2

cosФ

VLIL cosФ

(Watts)

(Watts)

=W /√3VLIL

(Watts)

(V) (A)

W1

W2

PROCEDURE:

7. Connections are made as per the circuit diagram. 8. The total voltage is given by adjust the autotransformer. 9. The meter readings are note down at no load conditions. 10. By applying the load gradually the corresponding meter readings are noted down. 11. The above procedure is repeated for different input voltage by adjust the autotransformer. 12. The load is released gradually and the supply is switched off. MODEL CALCULATION:

63

VIVA QUESTIONS:

2. What is balanced voltage? 3. What is balanced impedance? 4. What is phase sequence? 5. Write the relation between the line and phase value of voltage and current in a balanced star connected source load. 6. Write the relation between the line and the phase value of voltage and current in a balanced delta connected source/load. 7. Write the relation between the power factor wattmeter readings in two wattmeter Method of power measurement. 8. Name the methods used for power measurement in three phase circuits. RESULT:

Thus the measure the three phase power using two wattmeter method and also find the power factor value

64

EX. NO: 11

CHARACTERISTICS OF LVDT

Date: Aim: To study the characteristics of an LVDT position sensor with respect to the secondary output voltage. APPARATUS REQUIRED: Trainer Kit, Connecting Leads, Digital Multimeter. THEORY: Displacement transducer generally covers those mechanical elements which convert force into displacement and then displacement into electrical signals. The LVDT is basically a mutual induction type transducer with variable coupling between the primary and the two secondary coils. LVDT consist of primary coil, uniformly wound over a certain length of transducer and two identical secondary coils symmetrically wound on either side of a primary coil and away from the center as shown in the fig. The iron core is free to move inside the coils in either direction from the null (central) position. When the primary coil is excited by primary supply, the induced emfs of the secondary‟s are equal to each other with the core lying in the center or null position. The secondaries are connected in series opposition so that the resultant output is zero. Displacement of movable core in either direction from the null position will result in output voltage proportional to displacement but of opposite polarity. LVDT find a number of applications in both measurement and control system. The extremely fine resolution, high accuracy, and good stability make the device particularly suitable as a short-stroke, position-measuring device.

65

CIRCUIT DIAGRAM:-

Figure 1: LVDT CUTAWAY

Figure 2: LVDT CIRCUIT DIAGRAM

OPERATION PROCEDURE:11. To connect the LVDT sensor at the 9 pin connector. 12. Switch ON the ON\OFF switch and see the power indicator. The RED LED on the Front will glow. 13. Adjust the zero reading on the display by Zero Control trim pot. 14. Travel 20 mm through micrometer. 15. Adjust the span range by Span Control trim pot reading 20mm.

66

5. 6.

Connect digital multimeter at the output terminal to show voltage. Move 20 mm core and take the voltage reading displayed in multimeter.

7.

Now repeat step 7 and take at least 6-7 readings of voltage corresponding to core displacement.

8.

Tabulate the results.

PRECAUTIONS: - 1) Before switching on the power supply check the connections. Set all the ranges at the lower ranges. 6. Handle the kit in a proper manner. 7. Check the polarities of the Multimeter.

OBSERVATION TABLE:S.NO

CORE DISPLACEMENT IN

OUTPUT VOLTAGE IN

MM

VOLTS

RESULT: Plot a graph of output voltage against core displacement.

67

Ex.No: 12

CALIBRATION OF ROTAMETER

Date:

AIM:

To calibrate the Rotameter by measuring standard or known flow of fluid in the pipe.

APPARATUS REQUIRED:

Rotameter with Fluid flow measurement setup, Meter scale and Stop watch.

THEORY:

The Rota meter is basically a variable area flowmeter.In the differential head flow meter (Orifice meter, Venturi meter etc) the retraction is of fixed size and the pressure differential across it changes with the flow rate; whereas in the case of rotameter the size of the restriction is adjusted by an amount necessary to keep the pressure differential constant when the flow rate changes and the amount of adjustment required is proportional to the flow rate.

The Rota meter consists of a vertically tapered tube with a float which is free to move up or down within the tube. The free area between the float and the inside wall of the tube form an annular orifice. When there is no flow through the rotameter the float rests at the bottom of the metering tube where approximately the maximum diameter of the float is approximately the same as the bore of the tube. When the fluid enters the metering tube the float moves up and the flow area of the annular orifice increases. Thus the float is pushed upwards until the lifting force produced by the pressure differential across its upper and lower surface is equal to the weight of the float. At this juncture a calibrated scale printed on the tube or near it, provides a direct indication of the flow rate. Thus the distance through which the float has moved in order to attain a constant pressure difference across it, has become the measure of flow rate, for a fluid of given density and viscosity.

FORMULA: Actual Reading Ia = A.h t

% error = Actual Reading - Measured Reading Measured Reading

x 100 = I a- I m x 100 Im

68

TABULATION:

S.no Rota meter reading (lt/hr)

Time taken(sec)

Actual

T

Ia(lt/hr)

Im

reading % error = I a– I m x 100 Im

PROCEDURE:

3.

At fully closed condition of the valve, note down the load in the tank and the Rota meter

4.

Gradually open the valve and note down the level in the tank and Reservoir and also note down the Rota meter reading and the time taken for every 5 cm rise

5. 6.

Repeat the step 2 for different valve opening positions At fully open condition, note down the reading

7.

The graph is plotted between Percentage error and Indicated Reading

VIVA QUESTION: List the differential pressure flow meters Define coefficient of discharge Define Reynold‟s number List variable area flow meter List inferential type flow meter Define vena contracta Define d/D ratio State the principle of Rotameter

What are the types of rotameter?

RESULT:

Thus the calibration of rotameter was done and the error graph is drawn.

69

EX. NO.13

RTD AND THERMISTOR

Date:

Aim:

To convert the heat energy (Temperature) into electrical signal using RTD Transducer. APPARATUS REQUIRED:Trainer Kit, Water Heater, Connecting Leads. THEORY: RTD is resistance temperature detector. The resistance of a conductor changes with change in temperature, this property is utilized for measurement of temperature. The variation of resistance with temperature is represented by following relationships for most of the metals.

R = R0 [1+ 1T + 2 T+……..+

n T]

R0 = Resistance at temperature T = 0 1,

2,

n = Constants

Platinum is especially suited for this purpose, as it can withstand the high temperatures while maintaining high stability. The requirements of a good conductor material to be used in RTD are The change in the resistance of material per unit change in temperature should be less as large as possible. The material should have a high value of resistively so that minimum volume of material should be used for the construction of RTD. The resistance of the material should have a continuous and stable relationship with temperature. The most common RTD‟s are made of platinum, nickel or nickel alloys. The economical nickel wires are used for a limited range of temperatures. Metals most

commonly used for resistance thermometer along with their properties are listed below.

70

2– Wire configuration of RTD

71

TEMPERATURE RANGE RESISTANCE METAL

O

TEMPERATURE

C

MELTING POINT OC

COEFFICIENT

MIN

MAX

PLATINUM

0.39

-260

110

1773

COPPER

0.39

0

180

1083

NICKEL

0.62

-220

300

1435

TUNGSTEN

0.45

-200

1000

3370

PROCEDURE :1)Connect the RTD supplied to you at the input terminal. If Platinum RTD is used,copper wire must be connected to +ve input terminal (red) and constantan wire must be connected to –ve terminal (black). If Copper RTD is used, then iron wire must be connected to +ve input terminal. 4. Potentiometer marked „MAX‟ must be turned fully anticlockwise. 5. Ensure that water heater is ready and the container contains sufficient amount of water. Now switch on the heater supply. Connect output terminals of the RTD setup to input terminals of DPM. 6. Prepare a mixture of melting ice and keep the mixture stirring regularly. Immerse the RTD in the ice bath and adjust the pot. Marked minimum on the to get zero on the DPM. 7. When the water starts boiling, the potentiometer marked Max is adjusted to get an indication of the boiling point temperature (which is measured with the help of mercury in

the glass tight thermometer). Repeat steps 4 & 5 until u get satisfactory indication at 0 degree and at boiling point. 8. Turn OFF the heater so that water starts cooling. Note the indicating reading on DPM and the thermometer reading. Enter the observations in table no.1 given below and then plot the graph of thermometer reading on x-axis and thermocouple reading on y-axis choosing proper scales.

72

OBSERVATION TABLE:-

S. No.

Thermometer Reading in ºC

RTD Change in Resistance

At the end of the experiment the following points may be noted. 12. RTD output is fairly linear and there is good agreement in the reading shown by the RTD and the Thermometer. Calibration curve can be seen to be almost a straight line.

13. When the RTD is taken out of ice bath and immersed in boiling water,the rise in temperature is indicated almost instantaneously. This shows that the RTD has got very good time response. PRECAUTIONS:While connecting the RTD to the input terminals, observe correct polarity. A broken or unconnected RTD will give out of scale indication. Please ensure that the RTD tip does not touch the heater element directly. Proper earthing of the heater may be ensured. Proper stirring of hot water must be carried out.

Result: Thus the measurement of temperature using RTD has been done.

73

ADDITIONAL EXPERIMENT

Date: Open circuit and Short circuit tests on Single - phase transformer

Aim: 

 





To obtain the equivalent circuit of transformer.



To predetermine the efficiency and regulation of transformer. To predetermine the maximum efficiency of transformer





Apparatus required:

S.No.

Item

Type

Range

Quantity

Precaution:





Variac must be  kept in minimum position while switching on and switching off the supply.

 be used.

LPF wattmeter for O.C. test and UPF wattmeter for S.C. circuit test should 

Range fixing: O.C. Test: Full load primary current I1 

Full load capacity in VA Pr imary voltage V1

Full load secondary current I 2 

Full load capacity in VA Secondary voltage V2

Let both O.C. and S.C. test be conducted on primary side.

On O.C. test the current drawn by the transformer is about 5 – 10% of Full load Primary current.  Ammeter range is (0 - )A The rated primary voltage will be applied.  Voltmeter range (0 -

)V

74

Observation: O.C. Test:

S.C. Test: M.F. =

V0

I0

(Volts)

(Amps)

M.F. =

W0 (Watts)

Observed

Actual

Vsc

Isc

(Volts)

(Amps)

Wsc (Watts)

Observed

Actual

Equivalent circuit of the transformer referred to primary side: Circuit Diagram for O.C. & S.C. Tests on Single Phase Transformer: O.C. Test:

1- Variac

1- Transformer

S.C. Test:

75

1- Variac

1- Transformer

Variac Specifications

Transformer Specifications Capacity

O/P Voltage Py. Voltage Current Rating Sy. Voltage

Model Graphs:

% regulation

%

UPF

0.8 p.f. 0.6 p.f. Leading p.f.

UPF Lagging

Po Wattmeter: The current rating and voltage rating of Wattmeter are to be nearer to the value calculated above. On O.C. condition the reactive power drawn is more and the active power drawn is less. So power factor on no-load will be very low.

LPF wattmeter can be used. The range of wattmeter is ……… V, ……. A, LPF. S.C. Test: The voltage applied to the transformer primary to circulate rated full load current is about 5 to 10% of rated primary voltage.  The voltmeter range is (0 -

)V

Ammeter range is (0 - )A

The active power drawn by the transformer on S.C. condition is more and reactive power drawn is less. UPF wattmeter can be used. Range of wattmeter is ………V, ……….A, UPF.

76

Procedure:



With the help of Variac, apply rated voltage to the transformer in O.C. test and  circulate rated current in S.C. test. Note down the corresponding meter readings.

Model Calculation:

2 Equivalent Circuit: W Power factor on no load Cos0  0 VI

0 0

Working component of no load current, Iw = I0 Cos0 Magnetising component of no load current, I = I0 Sin0

Resistance to iron losses, R0 

V0 Iw

Reactance to magnetization of the core, X 0 

V0 I



W

Equivalent resistance of the transformer referred to primary, R  01 I

sc

2 sc

(assuming S.C. test is conducted on primary side)

77

Predetermination of Efficiency: Cos = 1 % of S. No.

Copper loss

T.L. =

Wc =X2Wsc

Wi + W c

load x

Po

(Watts)

0

2

20

3

40

4

60

5

80

6

100

7

120



Po

Pi

(Watt

(Watts

(Watts) )

1

Pi

(Watts

(Watts)

Cos = 0.8

Cos = 0.6

Po 

 (Watts)

s)

)

Pi (Watts)

78

Predetermination of Full load regulation:

S.No.

CosΦ

SinΦ

% Regulation Lagging p.f.

1 0

0.2 2 0.4 3 0.6 4 0.8 5 1.0 6

Leading p.f.

79

Equivalent impedance of the transformer referred to primary, Z01 

Vsc I sc

 Z

Equivalent leakage reactance of the transformer referred to primary, X 01

2

R

01

V2

Voltage transformation ratio, K 

V1 Equivalent resistance of the transformer referred to secondary, R02 = K2R01 Equivalent leakage reactance of the transformer referred to secondary, X02 = K2X01. I2‟ – Secondary rated current referred to Primary side V2‟ – Secondary rated voltage referred to Primary side

5. Predetermination of Efficiency: Let the load be x% of FL kVA and cos - load power factor

Power output, P0 = x (FL kVA) cos 1000 Copper Losses, Wc = x2 Wsc

Total Losses, W = Wi + Wc (where Wi is approx. equal to W0)

Power input Pi = P0 + W Efficiency,  

P0 Pi

5. Predetermination of Full load regulation: (I 2 R02 Cos  I2 X 02 sin) % Regulation = V2

 100

2 01

Where I2 - Full load secondary current. V2 - rated secondary voltage Cos - Load power factor +ve sign for lagging power factor load -ve sign for leading power factor load iv) Maximum Efficiency – predetermination:

For maximum , copper loss = Iron loss i.e. I2 2 R02 = Wi W

i

I Load current corresponding to maximum efficiency

2

 R 02

Then, maximum  can be determined for any load power factor as below.

81

Cos  -- load power factor (assume)

Power output, Po = V2I2 cos

Total losses, W = 2 Wi

Power output, Po = Pi + W

Maximum efficiency max 

Po

 100

Pi

Viva Question:

5. Why O.C test is conducted on the L.V side and S.C test on the H.V side? 6. Define regulation in a transformer. 7. What is the regulation of an Ideal transformer? 8. What is the condition for maximum efficiency of a transformer? 9. How no load losses are determined. 6.How copper losses are determined.

Result: Thus the SC test and OC test for a single phase transformer has been done.

81