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TABLE OF CONTENTS

1. Syllabus

2. Mapping of Program Outcomes with Instructional Objectives

3. Mapping of Program Educational Objectives with Program Outcomes

4. Session plan

5. Laboratory policies & Report format.

6. Evaluation sheet

7. Each experiment should be prefixed with prelab questions

with answer key and suffixed with post lab questions with

answer key.

8. Projects.

1

Syllabus 2

L T P C

EE 0209 ELECTRICAL MACHINES LAB - I 0 0 3 2

Prerequisite

EE 0201

PURPOSE

To give students a fair knowledge of testing different types of DC machines and transformers.

INSTRUCTIONAL OBJECTIVES At the end of the course the students will be able to:

1. Understand the performance and characteristics of DC machines and transformers.

2. Understand the testing of DC machines and transformers.

LIST OF EXPERIMENTS

1. Load test on DC shunt motor

2. Load test on DC Series motor

3. Speed Control of DC Shunt Motor.

4. Load test on DC shunt generator, DC compound generator.

5. Load test on single phase transformer.

6. Open circuit & Short circuit test on single phase transformer

7. Open circuit characteristics of DC generator (Self and Separately Excited)

8. Swinburne’s test and separation of losses in DC Machine.

9. Hopkinson’s test

10. Sumpner’s test on 1-phase transformers

11. 3-phase transformer connections

12. 3-phase to 2 -phase conversion

3

REFERENCE

Laboratory manual.

EE 0209 - ELECTRICAL MACHINES LAB - I (R) 1

2

Course designed by

Student outcomes

Department of Electrical and Electronics Engineering

a b c d e f g h i j k

x x x

Engineering

Basic Sciences

Category

3

Broad area (for ‘P’category)

General (G)

Electrical

Machines

x

Sciences and

(B) Technical

Arts(E)

Circuits Electronics

and

Systems

Professional Subjects(P)

x

Power Intelligent

System Systems

4 Course Coordinator Mrs. P.Sivasankari

4

Mapping of Program

Outcomes with Instructional

Objectives 5

Mapping of Program Instructional Objectives Vs Program Outcomes

Program Outcomes

Understand the Understand the

performance and testing of DC

characteristics of DC machines and

machines and transformers.

transformers.

a).An ability to apply x

knowledge of mathematics,

science, and engineering.

b). An ability to design and x x

conduct experiments, as

well as to analyze and

interpret results. e).An ability to identify, x

formulate, and solve engineering problems

6

Mapping of Program

Educational Objectives with

Program Outcomes 7

PROGRAM EDUCATIONAL

CRITERION 3 (a-k OUTCOMES) OBJECTIVES

1 2 3 4

(a) an ability to apply knowledge of X

mathematics, science, and engineering

(b) an ability to design and conduct X

experiments, as well as to analyze and

interpret data

(c) an ability to design a system, component, X

or process to meet desired needs within

realistic constraints such as economic,

environmental, social, political, ethical,

health and safety, manufacturability, and

sustainability

(d) an ability to function on multidisciplinary X X

teams

(e) an ability to identify, formulate, and X

solve engineering problems

(f) an understanding of professional and X

ethical responsibility

(g) an ability to communicate effectively in X

both verbal and written form.

(h) the broad education necessary to X

understand the impact of engineering

solutions in a global perspective.

(i) a recognition of the need for, and an X

ability to engage in life-long learning

(j) a knowledge of contemporary issues X

(k) an ability to use the techniques, skills, X X

and modern engineering tools necessary for

engineering practice.

8

Academic Course Description

SRM University, Kattankulathur

Faculty of Engineering and Technology

Department of Electrical and Electronics Engineering

COURSE : EE0209

TITLE : ELECTRICAL MACHINES LAB I

CREDIT : 01

LOCATION : DC Machines Lab

PREREQUISITES COURSES : EE0201-Electrical Machines - I

PREREQUISITIES BY TOPIC : NIL

Outcomes

Students who have successfully completed this course

Instructional Objective

The students will be able to:

Understand the performance and characteristics of DC

machines and transformers.

Understand the testing of DC machines and transformers

Program outcome

a) An ability to apply

knowledge of mathematics,

science, and engineering.

b) An ability to design and

conduct experiments, as

well as to analyze and

interpret data.

e) An ability to identify,

formulates, and solves

engineering problems.

9

Text book(s) and/or required materials:

1. B.L.THERAJA & A.K.THERAJA , vol II AC & DC

machines.

2. Electrical machines, Nagrath & kothari

3. Electrical machines lab I Manual

4. Electrical machines lab reference manual

Web Resources:

1. www.ncert.nic.in 2. www.electricalmachine.net

Professional component:

General

Basic Sciences

Engineering sciences & Technical arts

Professional subject

SESSION PLAN:

WEEK NAME OF THE

EXPERIMENT

I Load test on DC shunt motor

II Load test on DC Series motor

III Speed Control of DC Shunt

Motor.

IV Load test on DC shunt generator,

DC compound generator.

V Load test on single phase

transformer.

VI Open circuit & Short circuit test

on single phase transformer

VII open circuit characteristics of DC

generator (Self and Separately

Excited)

- 0%

- 0%

- 0%

- 100%

REFERENCE

1.B.L.THERAJA &

A.K.THERAJA , vol

II AC & DC

machines.

2.Electrical

machines lab I

Reference manual

OBJECTIVE

Understand the

performance and

characteristics of DC

machines and

transformers

10

http://www.ncert.nic.in/

http://www.electricalmachine.net/

VIII Swinburne’s test and separation of

losses in DC Machine.

IX Hopkinson’s test

X Sumpner’s test on 1-phase

transformers

XI 3-phase transformer connections

XII 3-phase to 2 -phase conversion

Understand the testing

of DC machines and

transformers

Understand the

performance and

characteristics of DC

machines and

transformers

Course Learning Outcome:

This course provides the foundation

education in electric circuit analysis and

design. Through lecture, laboratory, and

out-of-class assignments, students are

provided learning experience that enable

them to:

1. Understand the performance and

characteristics of DC machines and

transformers

2. Understand the testing of DC machines

and transformers

Correlates to

program outcome

H M L

H

H

H: high correlation, M: medium correlation, L: low correlation

11

EVALUVATION METHOD:

• Prelab Test - 10%

• Inlab Performance - 30%

• Postlab Test - 10%

• Attentance - 5%

• Record - 20%

• Final Exam - 25%

• Total - 100%

LABORATORY POLICIES AND REPORT FORMAT:

1. Lab reports should be submitted on A4 paper. Your report is a professional

presentation of your work in the lab. Neatness, organization, and completeness will be

rewarded. Points will be deducted for any part that is not clear.

2. The lab reports will be written individually. Please use the following format for your

lab reports.

a. Cover Page: Include your name, Subject Code, Subject title, Name

of the university.

b. Evaluation Sheet: Gives your internal mark split -up.

c. Index Sheet: Includes the name of all the experiments.

d. Experiment documentation: It includes experiment name, date,

objective,circuit diagram, simulated circuit and verified outputs.

e. Prelab and Postlab question should be retyped in the end of every

cycle.

3. Your work must be original and prepared independently. However, if you need any

guidance or have any questions or problems, please do not hesitate to approach your

staff incharge during office hours. The students should follow the dress code in the

Lab session.

4. Labs will be graded as per the following grading policy:

• Prelab Test - 10%

• Inlab Performance - 30%

• Postlab Test - 10%

• Attentance - 5%

• Record - 20%

• Final Exam - 25%

• Total - 100%

12

5. Reports Due Dates: Reports should be submitted at the end of each cycle. A late lab report

will have 20% of the points deducted for being one day late. If a report is 2 days late, a grade of 0

will be assigned.

6. Systems of Tests: Regular laboratory class work over the full semester will carry a

weightage of 75%. The remaining 25% weightage will be given by conducting an end

semester practical examination for every individual student if possible or by conducting a

1 to 1 ½ hours duration common written test for all students, based on all the experiment carried

out in the semester.

Prelab test is conducted at the beginning of each cycle as a written test and the post lab test

is conducted as viva-voce during the permission of report.

13

Pre-lab Questions 1. What is the working principle of generator?

2. What do you mean by Shunt Generator?

.

3. Write the EMF Equation of the Generator?

4. How may the number of parallel paths in an armature be increased?

5. How should a generator be started?

14

OPEN CIRCUIT AND LOAD CHARACTERISTICS OF DC SHUNT

GENERATOR

Aim:

To perform open circuit test and load test on the given DC shunt generator and to draw its

characteristics curves.

Apparatus Required:

S.No. Apparatus Range Type Quantity

1 Ammeter (0-1)A MC 1

2 Voltmeter (0-300)V MC 1

3 Rheostats 1250Ω, 0.8A Wire Wound 2

4 SPST Switch - - 1

5 Tachometer (0-1500)rpm Digital 1

6 Connecting Wires 2.5sq.mm. Copper Few

Precautions:

1. The field rheostat of motor should be in minimum resistance position at the time of

starting and stopping the machine.

2. The field rheostat of generator should be in maximum resistance position at the time

of starting and stopping the machine.

3. SPST switch is kept open during starting and stopping.

Procedure:

1. Connections are made as per the circuit diagram.

2. After checking minimum position of motor field rheostat, maximum position of

generator field rheostat, DPST switch is closed and starting resistance is gradually

removed.

3. By adjusting the field rheostat, the motor is brought to rated speed.

4. Voltmeter and ammeter readings are taken when the SPST switch is kept open.

5. After closing the SPST switch, by varying the generator field rheostat, voltmeter and

ammeter readings are taken.

15

6. After bringing the generator rheostat to maximum position, field rheostat of motor to

minimum position, SPST switch is opened and DPST switch is opened.

Formulate Used

1. Ia = Ir + IL

2. Eg = Ia Ra + VL

Tabular Column:

S.No. Ir (Amp) Eg (Volts)

Eo (

Volt

s)

Load Test

Sl.No. VL Ir IL Ia EG

(Volts) (Amp) (Amp) (Amp) (Volts)

Model Graph:

Critical Resistance = Eo / If Ohms

If

Eo

If (Amps)

Result:

Thus open circuit characteristics of self excited DC shunt generator are obtained and its critical

resistance is determined.

17

Post lab questions 1. What causes heating of armature?

2. How do we conclude theat connections between field coils and armature are correct?

3. When a generator loses its residual magnetism either due to lighting or short circuit ,how can it

be made to build up?

4.What are the causes of hot bearings?

5. Will a generator build up if it becomes reversed?

18

LOAD CHARACTERISTICS OF DC COMPOUND GENERATOR

Pre- Lab Questions:

1. How should a compound generator be started?

2. What in meant by build up of generator?

3. What is the procedure for shutting down a generator?

4. What is meant by armature reaction?

.

5. How are brushes connected in a dc generator?

19

LOAD CHARACTERISTICS OF DC COMPOUND GENERATOR

Aim:

To conduct a load test and to draw the external (or) load characteristics of the given

compound generator when it is,

(i) Cumulatively compounded

(ii) Differentially compounded

Apparatus Required:


(0-2)A MC 1 1 Ammeter

(0-20) A MC 1


3 Rheostats 1200Ω, 0.8A Wire Wound 2

4 Loading Rheostat 5KW, 230V - 1

5 Tachometer (0-1500)rpm Digital 1


Precautions:

1. The field rheostat of motor should be at minimum position.

2. The field rheostat of generator should be at maximum position.

3. No load should be connected to generator at the time of starting and stopping.

Procedure:


2. After checking minimum position of DC shunt motor field rheostat and maximum

position of DC shunt generator field rheostat, DPST switch is closed and starting

resistance is gradually removed.

3. Under no load condition, Ammeter and Voltmeter readings are noted, after

bringing the voltage to rated voltage by adjusting the field rheostat of generator.

4. Load is varied gradually and for each load, voltmeter and ammeter readings are

noted.

20

5. Then the generator is unloaded and the field rheostat of DC shunt generator is

brought to maximum position and the field rheostat of DC shunt motor to

minimum position, DPST switch is opened.

6. The connections of series field windings are reversed the above steps are

repeated.

7. The values of voltage for the particular currents are compared and then the

differential and cumulative compounded DC generator is concluded accordingly.

Tabular Column

Cumulative Compound

VL (Volts) IL (Amp)

V (

Volt

s)

Differential Compound

VL (Volts) IL (Amp)

Model Graph:

Cumulatively Compounded

Differentially Compounded

IL (Amps)

Result:

Thus load characteristics of DC compound generator under cumulative and differential mode

condition are obtained.

22

Post Lab questions:

1. What are the indication of an order loaded generator?

2. What are the causes of an overloaded generator?

3. What are the causes for the failure of generator to build up?

23

LOAD TEST ON DC SHUNT MOTOR Pre lab Questions:

1. Define Back EMF?

2. State the voltage equation of motor.

3. What is the condition for maximum power developed in motor?

4. Give an expression for the armature torque of a motor.

5. Give an expression for speed of DC motor

24

LOAD TEST ON DC SHUNT MOTOR

Aim:

To perform the load test on the given DC shunt motor and to draw the performance

characteristics

Apparatus Required:




3 Rheostat 1250Ω, 0.8A Wire Wound 1

4 Tachometer (0-1500) rpm Digital 1


Precautions:

1. DC shunt motor should be started and stopped under no load condition.

2. Field rheostat should be kept in the minimum position.

3. Brake drum should be cooled with water when it is under load.

Procedure:


2. After checking the no load condition, and minimum field rheostat position, DPST

switch is closed and starter resistance is gradually removed.

3. The motor is brought to its rated speed by adjusting the field rheostat.

4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no

load condition.

5. The load is then added to the motor gradually and for each load, voltmeter, ammeter,

spring balance readings and speed of the motor are noted.

6. The motor is then brought to no load condition and field rheostat to minimum

position, then DPST switch is opened.

25

Spee

d N

(rp

m)

Torq

ue

T (

Nm

)

Spee

d N

(rp

m)

Eff

icie

ncy

%

Formulae Used

1. Input power = V x I Watts

2. Torque = (9.81) x (S1 ~ S2) x R, N-m

2∏NT 3.

Output power

4. % efficiency =

Model Graphs:

y3 y2 y1

N

Watts 60

Output power x100% Input power

η

T

Output Power (Watts)

26

y

x

Torque T (Nm)

Tabular Column

Sl V I N Spring Balance Torque Input Output Efficiency

No. Volts Amp Rpm S1 S2 S1-S2 N-m Watts Watts %

Kg Kg Kg

Result:

The load test on the given dc shunt motor was connected and its performance

characteristics were drawn.

27

Post Lab Questions:

1. What will happen if the field of a dc shunt motor is opened?

2. Explain what happens of when dc moor is connected across an AC supply.

3. Why does a dc motor some time spark on light load?

4. What will happen if a shunt motor is directly connected to the supply line?

28

LOAD TEST ON DC SERIES MOTOR

Pre Lab Questions:

1. Explain the motor principle.

2. Define torque.

3. What do you mean by lost torque?

4. Give any two applications of DC series motor.

5. Is DC series motor a constant speed or variable speed motor.

29

LOAD TEST ON DC SERIES MOTOR

Aim:

To perform the load test on the given DC series motor and to plot its performance

characteristics

Apparatus Required:




(0-3000) 3 Tachometer Digital 1

rpm


Precautions:

1. The motor should be started and stopped with load

2. Brake drum should be cooled with water when it is under load.

Procedure:


2. After checking the load condition, DPST switch is closed and starter resistance is

gradually removed.

3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings

are noted.

4. After bringing the load to initial position, DPST switch is opened.

Formulae Used

1. Input power = W x I Watts

2. Torque = (S1 ~ S2)x 9.81 x R N - m

Where R is the radius of the brake drum

Circumference of the brake drum = 73 cm

(2 Π R) R = 0.116 m

2∏NT 3. Output power = Watts

60 Output power

4. Efficiency = x100% Input power

30

Torq

ueT

(Nm

)

Eff

icie

ncy

%

Sp

eed

N(r

pm

)

Tabular Column: Sl V I N Spring Balance Torque Input Output Efficiency

No. Volts Amp Rpm S1 S2 S1-S2 N-m Watts Watts %

Kg Kg Kg

Model Graph:

y3 y2 y1

T

E

N

Output Power

Result:

Thus load test on the DC series motor was conducted and its performance characteristics were

drawn.

31

Post Lab Questions: 1. Why series motor should always be started with some load?

2. What are the operating characteristics of DC series motors?

3. How do you fix the fuse rating of a DC machine?

32

SPEED CONTROL OF DC SHUNT MOTOR

Pre Lab Questions:

1. What are the factors controlling motor speed?

2. Name the various speed control methods flux control method,

3. Define stalling current.

4. What is the necessity of a starter?

33

SPEED CONTROL OF DC SHUNT MOTOR

Aim:

To control the speed of the given DC shunt motor by

a. Field control method

b. Armature control method

Apparatus Required:


1 Ammeter (0-20) A MC 1

2 Voltmeter (0-300) V MC 1

1250Ω, 0.8A Wire 3 Rheostats Each 1

50Ω, 3.5A Wound



Precautions:

1. Field Rheostat should be kept in the minimum resistance position at the time of

starting and stopping the motor.

2. Armature Rheostat should be kept in the maximum resistance position at the time of

starting and stopping the motor.

Procedure:


2. After checking the maximum position of armature rheostat and minimum position of

field rheostat, DPST switch is closed

(i) Armature Control:

1. The field current is kept constant and the armature voltage is varied in steps with the

help of armature rheostat and the corresponding speeds are noted down

2. The above procedure is repeated for different values of field current.

(ii) Field Control:

1. Supply is switched ‘ON’ and the motor is started

2. The armature voltage is kept constant and the field current is varied in steps and the

corresponding speeds are noted.

34

3. The above procedure is repeated for different values of armature voltage

Tabular Column:

1. Armature Control Method

Ir1 = 0.8A Ir2 = 0.7A

Sl.No. V N V N

Volts Rpm Volts Rpm

35

Spee

d N

(rp

m)

Spee

d N

(rp

m)

2. Field Control Method

Sl.No. Ir N Ir N

A Rpm A Rpm

Model Graphs:

If1

If2

If3

Va1

Va3 Va2

Va (Volts)

Result:

If (Amps)

The speed of the given dc shunt motor was controlled by armature control method and field

control method, and the speed characteristics were drawn.

36

Post Lab Questions:

1. What are the advantages of field control method?

2. What are merits of rheostatic control method?

37

SWINBURNE’S TEST

Pre Lab Questions:

1. For what kind of machines this test in applicable?

2. What are the advantages of this test?

3. What is the disadvantages of this test?

38

SWINBURNE’S TEST

Aim:

To predetermine the efficiency of DC shunt machine when it acts as a generator and motor.

Apparatus Required:


1 Ammeter (0-20) A MC 1

2 Voltmeter (0-300) V MC 1

Wire 3 Rheostats 1250Ω, 0.8A 1

Wound


5 Resistive Load 5KW,230V - 1


Precautions:

The field rheostat should be in the minimum position at the time of starting and stopping

the motor

Procedure:


2. After checking the minimum position of field rheostat, DPST switch is closed and

starting resistance is gradually removed.

3. By adjusting the field rheostat, the machine is brought to its rated speed.

4. The armature current, field current and voltage readings are noted.

5. The field rheostat is then brought to minimum position DPST switch is opened.

Formulae Used

Constant Losses Wc = Input power - Armature copper loss

= V x Io - (Io - Ir)2 x Ra

Where Ra is the resistance of the armature

39

For motor

(i) Ia - IL - If

(ii) Ia2 Ra

(iii) Total loss WT = WC + Ia2 Ra

(iv) Input power = V IL

Input Power − Total loss (v) Efficiency ηm = x100%

Input Power For Generator

(i) Ia - IL - If

(ii) Ia2 Ra

(iii) Total loss WT = WC + Ia2 Ra

(iv) Output power = V IL

Output Power (v) Efficiency ηG = x100%

Input Power +Total Loss

Model Graph:

As a Generator

% η

As a Motor

OUTPUT POWER P0

(W)

Tabular Columns:

V IO Ir

(Volts) (Amp) (Amp)

Motor

IL Ia=IL+Ir Ia2 Ra We WT =We+ Output Input %η A A Watts Watts Ia2 Ra Watts Watts

Watts

Generator

IL Ia=IL+Ir Ia2 Ra We WT =We+ Output Input %η A A Watts Watts Ia2 Ra Watts Watts

Watts

Result:

Thus the efficiency of the D.C shunt machine was predetermined when it is acting as a generator as well

as motor.

41

Post Lab Questions:

1. Why a three point starter is necessary for a DC shunt motor?

2 What is the precaution that should be followed?

3. What is the formula to find the efficiency of DC machine when running as a generator

and as a motor?

42

Pre Lab Questions:

1. What is the other name of Hopkinson’s test?

2. What is the main requirement in conducting Hopkinson’s test?

43

HOPKINSON’S TEST

Aim:

To conduct Hopkinson’s test on the given pair of DC machine and to obtain the

performance characteristics.

Apparatus Required:

S.No. Apparatus

1 Ammeter

2 Voltmeter

3 Rheostats

4 Tachometer

5 Resistive Load

6 Connecting Wires

Range

(0-1)A

(0-20) A

(0-300) V

(0-600)V

1250Ω, 0.8A

(0-3000) rpm

5KW,230V

2.5sq.mm.

Type

MC

MC

MC

MC

Wire

Wound

Digital

-

Copper

Quantity

1

2

1

1

2

1

1

Few

Precautions:

1. The field rheostat of the motor should be in the minimum position at the time of

starting and stopping the machine.

2. The field rheostat of the generator should be in the maximum position at the time

of starting and stopping the machine.

3. SPST switch should be kept open at the time of starting and stopping the machine.

Procedure:


2. After checking the minimum position of field rheostat of motor, maximum

position of field rheostat of generator, opening of SPST switch, DPST switch is

closed and starting resistance is gradually removed.

3. The motor is brought to its rated speed by adjusting the field rheostat of the motor.

4. The voltmeter V1 is made to read zero by adjusting field rheostat of generator and

SPST switch is closed.

5. By adjusting field rheostats of motor and generator, various Ammeter readings,

voltmeter readings are noted.

6. The rheostats and SPST switch are brought to their original positions and DPST

switch is opened.

44

Formulae Used

1. Power drawn from supply = Vs Is

2. Iam = IL + (Is - Ifm)

3. Armature copper loss in motor Iam2 Ram.

Where Ram is armature resistance of motor

4. Shunt field copper loss in generator = Vs Ifm

5. Iag = ILg + Ifg

6. Armature copper loss in generator = Iag2 Rag.

7. Shunt field copper loss in generator = Vs Ifg.

8. Total stray loss of both machines Ws =

Ws=Vs Is -[Iam2 Ram + Vs Ifm + Iag2 Rag +Vs Ifg]

W s

9. Stray loss of generator (or) motor = 2

10. W s

Total loss of motor WT = +Iam2 Ram + Vs Ifm 2

W s 11. Total loss of generator +Iam2 Ram + Vs Ifm

2 12. Output of generator = Vg. ILg

13. Input = Output + Total losses of generator

Output of generator 14. ηg = x100

Input of generator 15. Input of motor = Vs (Is + ILg)

16. Output of motor = Input of motor - Total losses of motor

45

17. ηm =

Output of motor x100 Input of motor

Tabular Column

Vs Is Ifm Vg Ifg ILg

(Volts) (Amp) (Amp) (Volts) (Amp) (Amp)

Generator

ILg Iag2 Ram

Shunt

Copper

Loss

Ws/2 WT

Output

Input

η %

Motor

ILg Iag2 Ram

Shunt

Copper

Loss

Ws/2 WT

Output

Input

η %

Model Graph:

As a Generator

%

As a

OUTPUT POWER P0

Result:

Thus Hopkinson’s test on the given pair of dc machines was conducted and the performance

characteristics were obtained.

46

Post Lab Questions

1. What is the advantages of this test?

2. What is the disadvantage of the test?

3. In rewinding the armature of a dc motor, progressive connections are changed to

retrogressive ones, will it affect the operation in anyway.

4. Why does dc motor some time run too fast when under load?

47

LOAD TEST ON SINGLE PHASE TRANSFORMER

Pre Lab Questions:

1. Define ideal transformer.

Its windings have no Ohmic resistance no magnetic leakage, no I2R and core

losses.

2. Give the transformer principle

Mutual induction.

3. Write the EMF equation of a transformer

E1 = 4.44 of N1 φm

E2 = 4.44 of N2 φm

4. Define voltage transformation ratio?

E N K = 2 2

= E N

1 1

48

LOAD TEST ON A SINGLE PHASE TRANSFORMER

Aim:

To conduct load test on the given single phase transformer and to draw its

characteristics.

Apparatus Required:

S.No. Apparatus

1 Ammeter

2 Voltmeter

3 Wattmeter

Range Type Quantity

(0-10)A MI 1

(0-5) A MI 1

(0-150)V MI 1

(0-300) V MI 1

(300V, 5A) Upf 1

(150V, 5A) Upf 1

4 Auto Transformer 1φ, (0-260)V - 1

5 Resistive Load 5KW, 230V - 1

6 Connecting Wires 2.5sq.mm Copper Few

Precautions:

1. Auto Transformer should be in minimum position.

2. The AC supply is given and removed from the transformer under no load condition.

Procedure:


2. After checking the no load condition, minimum position of auto transformer and

DPST switch is closed.

3. Ammeter, Voltmeter and Wattmeter readings on both primary side and secondary side

are noted.

4. The load is increased and for each load, Voltmeter, Ammeter and Wattmeter readings

on both primary and secondary sides are noted.

5. Again no load condition is obtained and DPST switch is opened.

49

Formulae:

1. % Efficiency η

2. % Regulation =

Tabular Column

Ws x100

Wp

V No load − V Load x100

V No Load

Vp Ip Wp (Watts) Vs Is Ws (Watts) % η %

(Volts) (Amps) OBS ACT (Volts) (Amps) OBS ACT Regulation

50

Eff

icie

ncy

η %

Reg

ula

tion R

%

Model Graphs:

η

R

Output Power (Watts) Result:

The load test on the single phase transformer was conducted and its characteristics

were drawn.

51

Post Lab Questions:

1. Why transformer rating is in KVA?

2. Define regulation of a transformer.

52

OC & SC TEST OF SINGLE PHASE TRANSFORMER Pre

Lab Questions:

1. What is the purpose of this test?

2. On which side of the transformer OC test in conducted?

3. On which side of the transformer SC test in conducted?

53

OPEN CIRCUIT & SHORT CIRCUIT TEST ON A

SINGLE PHASE TRANSFORMER Aim:

To conduct open circuit and short circuit test on the given single phase transformer and to

predetermine the efficiency and regulation of the transformer and also to draw the equivalent

circuit.

Apparatus Required:

S.No. Apparatus

1 Ammeter

2 Voltmeter

3 Wattmeter

4 Connecting Wires

Range Type Quantity

(0-2)A MI 1

(0-5) A MI 1

(0-150)V MI 2

(150V, 5A) LPF 1

(150V, 5A) UPF 1

2.5sq.mm Copper Few

Precautions:

1. Auto Transformer should be in minimum voltage position at the time of closing &

opening DPST Switch.

Procedure:

Open Circuit Test:


2. After checking the minimum position of Autotransformer, DPST switch is closed.

3. Auto transformer variac is adjusted get the rated primary voltage.

4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.

5. Auto transformer is again brought to minimum position and DPST switch is opened.

Short Circuit Test:


2. After checking the minimum position of Autotransformer, DPST switch is closed.

3. Auto transformer variac is adjusted get the rated primary current.

4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.

5. Auto transformer is again brought to minimum position and DPST switch is opened.

54

Tabular Column:

Open Circuit Test:

Vo Io Wo (Watts)

(Volts) (Amps) Observed Actual

Multiplication factor =

Short Circuit Test:

VSC

(Volts)

17.5

Voltage rating x current rating

Full scale deflection of wattmeter

ISC

(Amps) Observed

4.35 18

WSC (Watts)

Actual

72

Formulae Used:

1.

2.

W o

Cost φ0 = V Io o

Sin φ0 = 1− Cos 2φ o

V o

3. Ro = where Io cos φ0 = Iw I Cos φ

o o

V o

4. Xo = I Sinφ

where Io sin φ0 = Iμ

5. Ze1 =

6. Re1 =

o o

V SC

I SC

W SC

2 I SC

7. Xe1 = Z

2 2

−R

8.

9.

10.

e1 e1

V 2

K = V1

Re2 = K2 Re1

Xe2 = K2 Xe1

56

Predetermination of efficiency at

1. Core loss = Wo

⎡1 ⎣x

⎤ load

⎦

⎡1⎤

2

2. Copper loss = full load copper loss X ⎣

3. Total loss = core loss + copper loss

x ⎦

4. Output = V2 I2 cos φ where cos φ = 1 (or) 0.8 V2 = 115V

5. Input = Output + Total loss

6. % Efficiency = Output / Input x 100

Predetermination of Regulation

I R cosφ+ I X sinφ 2

Lagging PF =

I Leading PF =

2

e2 1 e2

V2

R cosφ− I X sinφ e2 1 e2

V 2

Tabular Column

Sl Load Core Copper Total Output Input %η No. Loss loss loss UPF 0.8 UPF 0.8 UPF 0.8

57

Load Cos φ Sin φ I2 Re2 I2 Xe2 % Regulation

Cos φ Sin φ Lag + Lead -

Equivalent Circuit:

ISCo

R

Io

Vo

Ro

N

Ro1 Xo1

L

O

A

D

Xo

58

ZL′ = ZL/K2

Eff

icie

ncy

η

%

Model Graphs:

Output power (Watts)

% lagging

Power factor

% leading

Result:

The open circuit and short circuit test on the given single phase transformer was

conducted and the efficiency and regulation of the transformer was predetermined and the

equivalent circuit was drawn.

59

Post Lab Questions:

1. On what factors the core loss of a transformer depends on?

2. What are two core losses?

.

60

SUMPNER’S TEST

Pre Lab Questions:

1. What is the requirement of Sumpner’s test?

2. What is the condition for maximum efficiency?

61

SUMPNER’S TEST

Aim:

To conduct Sumpner’s test on the given single phase transformers and to

predetermine the efficiency and regulation of the given transformers.

Apparatus Required:

S. No. Name of the Apparatus Range Type Quantity

1 Auto Transformer (0-270) V - 2

2 Wattmeter

3 Ammeter

4 Voltmeter

5 Connecting Wires

300 V, 10A LPF 1

75 V, 5 A UPF 1

(0-2) A MI 1

(0-20) A MI 1

(0-75) V MI 1

(0-150) V MI 1

2.5sq.mm Copper Few

Precautions:

1. Both the autotransformers should be kept at its minimum potential position.

2. SPST switch should be kept open, at the time of starting.

Procedure:

1. Connections are made as shown in the circuit diagram.

2. Rated voltage of 110V is adjusted to get in voltmeter by adjusting the variac of the

Auto Transformer which would be in zero before switching on the supply at the

primary side.

3. The readings of voltmeter, ammeter and wattmeter are noted on the primary side.

4. A voltmeter is connected across the secondary and with the secondary supply off i.e

switch S is kept open. The voltmeter reading is noted.

5. If the reading of voltmeter reads higher voltage, the terminals of any one of secondary

coil is interchanged in order that voltmeter reads zero.

6. The secondary is now switched on and SPST switch is closed with variac of auto

transformer is zero.

7. After switching on the secondary the variac of transformer (Auto) is adjusted so that

full load rated secondary current flows.

8. Then the readings of wattmeter, Ammeter and voltmeter are noted.

62

9. The Percentage Efficiency and percentage regulation are calculated and equivalent

circuit is drawn.

Tabular Column

Vo Io Wo Vs Is Ws (Watts)

(Volts) (amp) (Watts) (Volts) (Amp)

OBS ACT OBS ACT

Formulae Used:

1.

2.

Vs

Vs1 = 2

Secondary current thro each transformer Is1 = Is

W s

3. Power input to secondary Ws1 =

W V

2

4. Re1 = I

s1 2 Ze1 = e1

2 2

s1

I s1

5. Xe1 = Z −R e1 e1

W /2 6. Cos φ =

V 0 2

, Sin φ = 1−cos φ Io o /2

63

7. Ro = I

o

V o V o

, Xo = /2cosφ I /2sinφ

o

8.

9.

10.

V s

K = V p

Re2=K2 Re1

Xe2 = K2 Xe1

⎡1 ⎤ Predetermination of efficiency at ⎣

1. Core loss = Wo

load⎦ x

⎡1⎤

2

2. Copper loss = full load copper loss x ⎣x⎦ 3. Total loss = core loss + copper loss

4. Output = V2 I2 cos φ where cos φ = 1 (or) 0.8 V2 = 115V

5. Input = output + Total loss

6. % Efficiency = Output / Input x 100

Predetermination of Regulation

I R cosφ+ I X sinφ 2

Lagging PF =

Leading PF =

e2 2 e2

V 2

I2Re2 cosφ− I 2 X e2 sinφ

V 2

Tabular Column

Sl Load Core Copper Total Output Input %η No. Loss loss loss UPF 0.8 UPF 0.8 UPF 0.8

64

% E

ffic

iency

% R

egula

tion

Load Cos φ Sin φ I2 Re2 I2 Xe2 % Regulation

Cos φ Sin φ Lag + Lead -

Model Graphs:

Cos φ = 1

Cos φ = 0.8 (Lead & Cos φ = 1

Lag Cos φ = 0.8 Lag

Cos φ = 0.8 Lead

Secondary Current (Amps)

Secondary Current (Amps)

Result:

The Sumpner’s test on the given two single phase transformers was conducted and the

efficiency and regulation was predetermined.

65

Post Lab Questions

1. What is an auto transformer?

2. What are losses in a transformer?

3. Compare all day efficiency Vs

66

PARALLEL OPERATION OF SINGLE PHASE TRANSFORMER

Pre Lab Questions:

1. What is the condition that has to be satisfied for the parallel operation of transformer?

67

PARALLEL OPERATION OF TWO SINGLE PHASE TRANSFORMER

Aim:

To connect two single phase transformer in parallel and to conduct the load test on the parallel

connected transformers

Apparatus Required:

S. No. Name of the Apparatus

1 Ammeter

2 Voltmeter

Range Type Quantity

(0-10A) MI 2

(0-20A) MI 2

(0-300V) MI 2

(0.150V) MI 1

3 Wattmeter 300V, 10A UPF 1

Precautions:

1. Auto transformer should be kept at minimum potential position

2. SPST switch should be kept open at the time of starting

3. There should not be any load at the time of starting

Procedure

1. Observing the precaution, the autotransformer -1 is adjusted to bring rated voltage on

the primary side.

2. The voltmeter reading across the SPST switch is checked, if the voltmeter across

SPST reads zero, the SPST switch is closed, if not the secondary terminals of any one

of the transformer is interchanged and then SPST switch is closed.

3. Load is applied gradually till rated current and all the meter readings are noted down.

Connections for Satisfactory Parallel Operation

1. Voltage ratings of the primary windings should be suitable for supply voltage and

frequency. The turn ratio of the transformer must be equal.

2. Transformers should be properly connected with regard to their polarity

3. The percentage impedance of the two transformers should be equal.

68

Tabular Column

Vp Ip Wp (Watts) Is1 Is Is Vs Output η % Volts Amps OBS ACT Amps Amps Amps Volts Watts

Model Graph:

Result:

Two single phase transformers were connected in parallel and the load test was

conducted on the parallel connected transformers.

69

Post Lab Questions:

1. Does the transformer draw any current when its secondary in open?

2. Why?

70

THREE PHASE TRANSFORMER CONNECTION

Pre Lab Questions:

1. What are the possible three phase connections?

2. Mention the instrument transformers

71

THREE PHAE TRANSFORMER CONNECTIONS

Aim:

To connect the primary and secondary of the given 3 phase transformer in the

following different configurations and to conduct the load test on the same.

1. Star-Star connection

2. Delta - Delta connection

3. Delta - Star connection

4. Star-Delta connection

5. Scott connection

Apparatus Required:

S. No. Name of the Apparatus Range Type Quantity

1 Ammeter (0-5A) MI 2

2 Voltmeter

3 Wattmeter

(0-600V) MI 1

(0-600V) MI 1

600V, 5A UPF 1

300V, 5A UPF 1

Precaution:

1. The 3 phase variac should be kept in minimum potential position

2. There should not be any load at the time of starting

Procedure

1. The 3 phase transformer is connected in any one of the configurations as

mentioned above.

2. The 3 phase variac is varied gradually and rated voltage is applied to the

transformer.

3. Then load is applied gradually till rated current and the corresponding meter

readings are noted down.

4. The above procedure is repeated for all the configurations.

Formulae Used

1. Input = Wp watts

2. Output power = Ws Watts

3. % Efficiency = Wp / Ws x 100 %

72

THREE PHASE TRANSFORMER CONNECTIONS


73



74

Model Graph:

Tabular Column

Sl. Vp Ip Vs Is Wp Ws % η No. (Volts) (Amps) (Volts) (amps) (Watts) (Watts)

OBS ACT OBS ACT

Result:

The three phase transformer was connected in different configurations and the load test was

conducted on the same.

75

Pre Lab Questions:

1. What is biggest advantage of T -T connection over V - V connection for 3 phase

power transformer?

2. Which connection is best suited for 3 phase 4 wire service?

76

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