Me 2209 Elece Engg Lab for Mech Final

ELECTRICAL ENGINEERING LAB MANUAL SRINIVASAN ENGINEERING COLLEGE, PERAMBALUR

II YEAR

SRINIVASAN ENGINEERING COLLEGEMECHANICAL ENGINEERING

ANNA UNIVERSITY CHENNAI

REGULATION 2008

II YEAR MECH / III SEMESTER

ME 2209- ELECTRICAL ENGINEERING LABORATORY ISSUE: 01 REVISION: 00

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II YEAR

APPROVED BY PREPARED BY

Prof.B.REVATHI M.P.SELVAKUMAR/AP/ECE

HOD/ECE R.RAJESH/PROF/ECE

Preface

This laboratory manual is prepared by the Department of Electronics and Communication

Engineering for Electrical Engineering (ME 2209) laboratory. This lab manual can be used as

instructional book for students, staff and instructors to assist in performing and understanding the

experiments. In the manual, experiments as per syllabus are described. This manual will be available

in electronic form from College’s official website, for the betterment of students.

Acknowledgement

We would like to express our profound gratitude and deep regards to the support offered by

the Chairman Shri. A.Srinivasan. We also take this opportunity to express a deep sense of gratitude

to our Principal Dr.B.Karthikeyan, M.E, Ph.D., for his valuable information and guidance, which

helped us in completing this task through various stages. We extend our hearty thanks to our head

of the department Prof.B.Revathi Sekar, M.E, (Ph.D)., for her constant encouragement and

constructive comments.

Finally the valuable comments from fellow faculty and assistance provided by the

department are highly acknowledged

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S.No TOPIC PAGE NO

1 Syllabus 4

2 Lab Course Handout 5

3 Learning Objectives 8

4 Experiments

1. Load test on D.C. shunt& D.C motor 9

2. Open circuit and load characteristics of self-excited D.C. shunt generator

15

3. Speed control of D.C. Shunt motor(Armature& Field Control) 19

4. Load test on single phase transformer 22

5. Open Circuit and Short Circuit test on single phase transformer 25

6. Regulation of three phase alternator by EMF and MMF methods 30

7. V Curves and Inverted V Curves of Synchronous Motor 34

8. Load test on three phase Squirrel Cage Induction motor 37

9. Speed Control of three phase Slip Ring Induction Motor 40

10. Load test on single phase Induction motor 42

11. Study of D.C. & A.C motor starters 46

5 Viva Question 55

.

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SYLLABUS

ME 2209 – ELECTRICAL ENGINEERING LABORATORY

LIST OF EXPERIMENTS

1. Load test on D.C. shunt& D.C motor.

2. Open circuit and load characteristics of self-excited D.C. shunt generator.

3. Speed control of D.C. Shunt motor (Armature& Field Control).

4. Load test on single phase transformer.

5. Open Circuit and Short Circuit test on single phase transformer.

6. Regulation of three phase alternator by EMF and MMF methods.

7. V Curves and Inverted V Curves of Synchronous Motor.

8. Load test on three phase Squirrel Cage Induction motor.

9. Speed Control of three phase Slip Ring Induction Motor.

10. Load test on single phase Induction motor.

11. Study of D.C. & A.C motor starters.

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LAB COURSE HANDOUT

Subject code : ME 2209Subject Title : Electrical Engineering LabStaff name : M.P.Selvakumar & R.Rajesh

Scope and Objective of the Subject:

To expose the students to the basic operation of electrical machines and help them develop experimental skills.

To study the concepts, performance characteristics, time and frequency response of linear systems and study the effects of controllers.

Course Plan / Schedule:

S.No Topics to be coveredLearning objectives Page

No*No. of hours

1Load test on D.C. shunt& D.C motor

Students will be exposed to the performance characteristics D.C. shunt & Series motors.

9

3 hrs.

2Open circuit and load characteristics of self-excited D.C. shunt generator

Students will be exposed to the concepts of Critical resistance(Rc), O.C.C at the specified speed, External Characteristics, and Internal Characteristics.

15

3hrs

3Speed control of D.C. Shunt motor (Armature& Field Control).

Students will understand speed control methods of D.C. shunt motor and the relation between armature voltage, field current and speed of D.C. Shunt motor.

19

3hrs

4Load test on single phase transformer

The students will understand direct load test on the given single phase transformer and determination procedures of efficiency and regulation at different loads.

22

3hrs

5Open Circuit and Short Circuit test on single phase transformer

The students will understand O.C and S.C tests, Equivalent circuit & Predetermination procedures of efficiency and regulation at different loads

25

3hrs

6 Regulation of three phase alternator by EMF and MMF methods

Students will be exposed to the concepts of predetermination of Voltage regulation by EMF & MMF

30 3hrs

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methods. Students will be exposed to the performance characteristics of the machine

7V Curves and Inverted V Curves of Synchronous Motor

Students will be exposed to relation between field current, armature current and power factors at various load levels.

34

3hrs

8Load test on three phase Squirrel Cage Induction motor

Students will be exposed to the performance characteristics of the three phase Squirrel Cage Induction motor.

37

3hrs

9Speed control of three phase slip ring induction motor.

Students will be exposed to the effect of stator voltage and rotor resistance on the speed of the three phase slip ring induction motor.

40

3hrs

10Load test on single phase Induction motor

Students will be exposed to the performance characteristics of single phase Induction motor.

423hrs

11Study of D.C. motor and induction motor starters

Students will be exposed to different kinds of D.C and induction motor starters

46

3hrs

*-As in Lab Manual

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Evaluation scheme – Internal Assessment

Timings for chamber consultation: Students can contact the Course Instructor in her/his chamber during lunch break.

STUDENTS GUIDELINES

There are 3 hours allocated to a laboratory session in Electrical Engineering and Control System Lab. It is a necessary part of the course at which attendance is compulsory.

Here are some guidelines to help you perform the Experiments effectively:

1. Read all instructions carefully and proceed according to that.2. Ask the faculty if you are unsure of anything program or any concept.3. Write up full and suitable conclusions for each experiment.4. After completing the experiment complete the observation and get signature from the staff.5. Before coming to next lab make sure that you complete the record and get sign from the

faculty.

STAFF SIGNATURE HOD

LEARNING OBJECTIVES

7

EC No.

Evaluation Components

Duration Weightage

1 Observation Continuous 20%2 Record Continuous 30%3 Attendance Continuous 30%4 Model lab 3hr 20%


II YEAR

1. To expose the students to the basic operations of electrical machines and to help them develop

their experimental skills.

2. To study the concepts, performance characteristics of electrical machines and starters

.PRECAUTIONS: (Not to be included in the Record)

1. Fuse carriers must be removed while giving electrical connections to Equipments.

2. Sliding contact positions of the various rheostats must be checked before starting the

Experiment.

3. SPST/DPST/TPST switches must be kept open till staff members verify and approve the

connections.

4. The following Guidelines must be followed for selection of appropriate Fuse, Meter and

Rheostat ranges:

Fuses for Motor/Generator sets

(i) For no-load tests -45% of rated current.

(ii) For Load tests-120% of rated current

Fuses for Transformers

(i) For no-load tests -10% of rated current.

(ii) For Load tests-120% of rated current

Meter range

Meters of nearest higher range available can be selected

Rating of Rheostat:

(i) Current rating- should be selected based on the basis of the current rating of the

circuit, to be fed through the rheostat.

(ii)Resistance rating- should be selected based on the current limitations/Speed

limitations to be imposed to the circuit fed through the rheostat.

5. Fuse carriers with appropriate fuse wires must be inserted into the fuse holders/bases and the

Experiment must be carried out after the circuit connections are checked and approved by the staff-

in-charge.

Ex. No: 1.ADate:

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LOAD TEST ON DC SHUNT MOTOR

Aim:To conduct load test on DC shunt motor and compound motor and draw the characteristic

curves

ExerciseDraw the following characteristic curves for DC shunt motor

i. Output Vs η% ii. Output Vs T

iii. Output Vs N iv. Output Vs IL v. Torque Vs N

Apparatus Required:Sl.no Name of the component type Range Quantity

-

Name plate details:MOTOR

Fuse rating calculation for field and armature:Load test 120 % of rated current

Formulae Used:

(i) Torque = in N-M

S1, S2 – spring balance readings in KgR- Break drum radius in m

(ii) Input power = V x I in Watts(iii) Output power = 2NT / 60 in Watts

N – Speed of the motor in RPM(iv) Percentage of efficiency = (Output power /Input power) x 100.

CIRCUIT DIAGRAM FOR LOAD TEST ON DC SHUNT MOTOR

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Precautions Starter should be in off position before switching on the supply. The DPST switch must be kept open. The motor field rheostat must be kept at minimum resistance position There should be no load on the motor at the time of starting. Before connecting the meters check the polarity and zero error.

Procedure for load test on DC shunt motor Connections are given as per the circuit diagram. Observe the precaution and using three-point starter the motor is started to run at the

rated speed by adjusting the field rheostat if necessary. The meter readings are noted at no load condition. By using break drum with spring balance arrangement the motor is loaded and the

corresponding readings are noted up to the rated current. After observation of all the readings the load is released gradually The motor is switched off by using DPST switch.

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TABULATION FOR LOAD TEST ON DC SHUNT MOTOR

Radius of the brake drum (R) = in m Thickness of the belt (t) = in m

Sl No

Load Voltage

in Volts

Load current

I Amps

speed in

rpm

Spring balanceReading

In kg

Input Power

in Watts

Torque in NM

Output Power

in Watts

Efficiency in %

S1 S2S1S

2

MODEL GRAPH(A) Electrical characteristics

11

in %

T in N-m

Speed in rpm

IL in Amps

N IL T %

Output power in watts


II YEAR

(B) Mechanical characteristics

(C) Torque, Speed Vs Load current

Model calculation:

Graph: Output Vs η% Output Vs T Output Vs N

12

T Vs N

Spe

ed (

N)

in r

pm

Torque ( T ) in N-m

Torq

ue (

T)

in N

-m

Spe

ed (

N)

in r

pm

IL Vs N

Load current (IL) in Amps

IL Vs T


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Output Vs IL Torque Vs N

Result:

EXPT. No: 1.BDate:LOAD TEST ON DC SERIES MOTOR

AIM:To conduct load test on the given DC Series Motor and determine the performance characteristics.

APPARATUS REQUIRED:

Sl.no Description Type Specification Quantity

PRECAUTIONS:1. The motor should be started and stopped with load2. Brake drum should be cooled with water when it is under load.PROCEDURE:1. Connections are made as per the circuit diagram.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.

CIRCUIT DIAGRAM:

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TABULAR COLUMN:

MODEL GRAPH:

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RESULT:

Ex. No: 2Date:

OCC AND LOAD CHARACTERISTICS OF SELF EXCITED D.C SHUNT GENERATOR Aim:

To conduct no load and load test on self excited generators and obtain the characteristics

Exercise1. Obtain the open circuit characteristics (OCC) of a self excited D.C generator

and determine critical resistance.2. Draw the external and internal characteristics of a self excited D.C generator.

Name plate details:Motor Generator

Apparatus Required:

Sl.no Description Type Specification Quantity

15

in %

T in N-m

Speed in rpm

IL in Amps

N IL T %

Output power in watts


II YEAR

Formula used:Generated voltage Eg = VL + Ia Ra

Precautions1. Motor side field rheostat should be kept at minimum resistance position.2. Generator side field rheostat should be kept at maximum resistance position.3. Starter should be in off position before switching on the supply.4. The DPST switch must be kept open.

Circuit diagram for open circuit and load test on D.C. Self-Excited Shunt Generator

Procedure for open circuit test2. Connections are given as per the circuit diagram.3. The motor is started with the help of THREE POINT starter.4. Adjust the motor speed to rated speed by adjusting motor field rheostat when the generator is

disconnected from the load by DPST switch 2.5. By varying the generator field rheostat gradually, the open circuit voltage [Eo] and

corresponding field current (If) are tabulated up to 120 % of rated voltage of generator.

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6. The motor is switched off by using DPST switch 1 after bringing all the rheostats to initial position.

Procedure for Load test:1. Connections are given as per the circuit diagram2. The prime mover is started with the help of three point starter and it is made to run at rated speed

when the generator is disconnected from the load by DPST switch 2.3. By varying the generator field rheostat gradually, the rated voltage [Eg] is obtained.4. The ammeter and voltmeter readings are observed at no load condition.5. The ammeter and voltmeter readings are observed for different loads up to the rated current by

closing the DPST switch 2.6. After tabulating all the readings the load is brought to its initial position.7. The motor is switched off by using DPST switch 1 after bringing all the rheostats to initial

position.

Tabulation for Open Circuit Test on Separately Excited D.C Shunt Generator:

Sl.no Field current in Amps [If]

Open circuit voltage in Volts [Eo]

Tabulation for Load Test:

Sl.no

Load current [IL] in Amps

Load voltage [VL] in Volts

Field current If in

amps

Armature current [Ia] in Amps

(Ia=If+IL)

Armature drop=

Ia* Ra in volts

Generated emf [Eg = VL+IaRa] in

volts

Circuit diagram for find the generator armature resistance [Ra]

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Procedure for find armature resistance Ra:1. Connections are given as per circuit diagram 2. Check loading rheostat must be at maximum resistance position.3. Close the DPST switch and vary the loading rheostat for various values in steps and noted

the corresponding voltmeter and ammeter reading.4. Open the DPST switch after loading rheostat begins its initial position.

Tabulation for Finding Armature Resistance:

Sl.noArmature voltage

Va in voltsArmature current

Ia in ampsRa = Va/ Ia in ohms

Model graphOpen circuit characteristics

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Internal (Eg Vs Ia) and External (VL Vs IL) characteristics

Result:

19

If

Field current [If] in amps

Ope

n ci

rcui

t vo

ltag

e in

V

olts

[E

o]

Eo Vs If

Load current [IL] in ampsArmature current [Ia] in amps

Loa

d vo

ltag

e in

Vol

ts [

VL]

Gen

erat

ed e

mf

in V

olts

[E

g]

Eg Vs Ia

VL Vs IL


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Ex. No: 3Date:

SPEED CONTROL OF DC SHUNT MOTOR

AimTo study the speed control characteristics of DC shunt motor (Armature control and Field

control)

Exercise

1. Draw the following curves for a. If Vs N at Different fixed values of Va b. Va Vs N at different fixed values of If


Name plate details:

MotorSpeed Type

Field Armature

Fuse rating calculation:

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CIRCUIT DIAGRAM

Precaution:

The DPST switch must be kept open while giving connections. At the time of starting, the motor field rheostat must be kept at minimum

resistance position and the armature rheostat must be kept at maximum resistance position.

Before connecting the meters check the polarity and zero error.Procedure

Connections are given as per the circuit diagram. Observe the precaution and switch ON the supply. By adjusting the field rheostat get the motor speed to rated speed

A. Armature Control Method Keep the Field Current Constant By adjusting armature rheostat the speed and armature voltage are noted. Repeat the same procedure for various positions.

B. Field Control Method Keep the armature voltage constant. By adjusting the field rheostat various field currents and voltage are noted. Repeat the same procedure for various positions

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Tabulation for Armature Control Method

Field current If1 Field current If2

Armature voltage Va

Speed N in RPMArmature

voltage VaSpeed N in

RPM

Tabulation for Field Control Method

Armature Voltage Va1 Armature Voltage Va2

Field Current If

In AMPSSpeed N in RPM

Field Current If In AMPS

Speed N in RPM

MODEL GRAPH:

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Result:

EXPT NO: 4. Date :

LOAD TEST ON SINGLE PHASE TRANSFORMER

AIM: To conduct a direct load test on the given single phase transformer and to determine the efficiency and regulation at different load conditions.

NAME PLATE DETAILS: KVA rating = Rated H.V side Voltage = Rated L.V side Voltage =

INSTRUMENTS AND EQUIPMENTS REQUIRED: S.No Equipment Type Range Quantity

1.

2.

3.

4.

5.

THEORY:

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Direct load test is conducted to determine the efficiency characteristics and regulation characteristics of the given transformer.

An ideal transformer is supposed to give constant secondary voltage irrespective of the load current. But, practically the secondary voltage decreases as the transformer is loaded due to primary and secondary impedance drops. Since these drops are dependent on load current, this variation in terminal voltage is found using direct loading.

PRECAUTIONS:1. Remove the fuse carriers before wiring and start wiring as per the circuit diagram.2. Fuse Calculations: This being a load test, the required fuse ratings are 120% of rated current.

CIRCUIT DIAGRAM:

PROCEDURE:1. The circuit connections are made as per the circuit diagram as shown in figure.2. Keeping the autotransformer in its minimum position and the DPST switch in open position, the main supply is switched ON.3. By slowly and carefully operating the Auto transformer the rated voltage (115V) is applied to the L.V side of the transformer.4. Under no-load condition, one set of readings namely VH.V, IH.V, WH.Vs, VL.V, WL.V, are recorded in the tabular column.5. The DPST switch on the load side is now closed and the load is increased in gradual steps and at each step all meter readings are noted down in the tabular column.6. The procedure is continued until the current on the H.V side is equal to its full load value.

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7. After the experiment is completed, the load is decreased to its minimum, the auto transformer is brought back to its original position and then the main supply is switched OFF.

CALCULATIONS:-

I. EFFICIENCY CALCULATION:

i . The efficiency of the transformer for each set of reading is calculated and tabulated using the expression,

100% XInput

Output

where, The output of the transformer = WH.V on the H.V side The input of the transformer = WL.V = Wattmeter reading on the L.V side

ii . A Graph is plotted between the percentage efficiency and the output, taking % efficiency on Y-axis and the output on X-axis, as shown in figure.

II . VOLTAGE REGULATION (down) CALCULATIONS: - i . The regulation is calculated and tabulated for each set of readings using the expression ,

100Re%)(.

)(.)(. XV

VVgulation

NoloadVH

loadVHNolaadVH

where, VH.V(No-load) - is the no-load voltage on the H.V side . VH.V(Load) - is the actual voltage on the H.V side under load condition . ii . A Graph is plotted b=ween the percentage regulation and the output taking % regulation on Y-axis and the output on X- axis as shown in figure.

TABULAR COLUMN:Sl.No

Input Out put (%) %V reg

VL.V IL.V WL.V

(W)VH.V

(V)IH.V

(A)WH.V

(watts)

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MODEL CALCULATION:

MODEL GRAPH:

RESULT: -

Ex. No: 5Date:

OC AND SC TESTS ON SINGLE PHASE TRANSFORMER

Aim:To conduct open circuit and short circuit test and to predetermine the efficiency of the

transformer at desired load and power factor and to calculate the regulation at different power factorExercise

1. Determine the equivalent circuit of the transformer.2. Predetermine the efficiency at different load at UPF and 0.8 Power factor lagging.3. Predetermine the full load regulation at different power factor.4. Draw the following curves

a. Output Vs η% b. Power factor Vs %Regulation


-

Name plate details:

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Transformer

Fuse calculation for transformer (O.C and S.C test):Primary current IP = KVA rating of the transformer /primary voltage.Secondary current IS =KVA rating of transformer / secondary voltage.O.C test10 % of rated primary currentS.C test125 % of rated secondary currentFormulae Used:Open circuit test:

1. No load power factor

WOC = open circuit power in watts VOC = open circuit voltage in voltsIOC = open circuit current in amps

2. No load working component resistance (RO); in ohms

3. No load magnetizing component (XO); in ohms

Short circuit test:

4. Equivalent impedance referred to HV side (Z02); in ohms.

5. Equivalent resistance referred to HV side (R02); in ohms

6. Equivalent reactance referred to HV side (X02); in ohms

7. Transformation ratio (K);

8. Equivalent resistance referred to LV side (R01); in ohms

9. Equivalent reactance referred to LV side (X01); in ohms

Efficiency and regulation 10. Output power = in watts11. Chopper loss = in watts

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12. Total loss WT = in watts

13. Efficiency = in %

14. Regulation = in %

Precautions:1. Auto transformer should be kept at zero volt position.2. At the time of starting the experiment DPST switch kept open and transformer should be no

load.3. High voltage and low voltage sides of the transformer should be properly used as primary or

secondary respective to experiments.Procedure (for Open circuit Test)

Connections are given as per the circuit diagram. Ensuring the precautions, supply is switched on by closing DPST switch. Auto transformer is adjusted to energize the transformer with primary voltage on LV side. Voltmeter, ammeter and wattmeter readings are noted at no load condition. Auto transformer is gradually decreased to its initial position. Switch off the supply by DPST.

Procedure (for Short CKT Test) Connections are given as per the circuit diagram. Ensuring the precautions the supply is switched on by closing DPST switch. Auto transformer is adjusted to energize the transformer with primary current on the HV

side. Voltmeter, ammeter and wattmeter readings are noted at no load condition. Auto transformer is gradually decreased to its initial position. Switch off the supply by DPST.

Circuit diagram for open circuit test of 1 transformer

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Circuit diagram for short circuit test of 1 transformer

Tabulation for OC Test multiplication factor:

Sl. no

Open circuit primary current

(IOC)In Amps

Open circuit primary voltage (VOC) in Volts

Open circuit power (Woc) in Watts

Open circuit Secondary

voltage in voltsObserved Actual

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Tabulation for SC Test multiplication factor:

Sl. No

Short circuit primary current

(ISC)In Amps

Short circuit primary voltage (VSC) in Volts

Short circuit power (Wsc) in Watts

Short circuit Secondary

Current in AmpsObserved Actual

Predetermination of efficiency:Core (or) Iron loss (Wi) = Watts, KVA rating of Transformer = . Rated Short circuit current = Amps Short Circuit power at rated current (WSC) = .

Fraction of load/Load factor (X)

Output power1000* in watts at Various P.F

Copper loss at various

loads

in watts

Total lossin watts WT= (Woc ) +(X2 *Wsc)

Efficiency at Various P.F

* (100 ) in %

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1¼½¾1

Tabulation to predetermine % Voltage regulation:ISC = RO2= XO2= V2O=Load factor

% V regulation at loads of Leading p.f

Unity p.f

% V regulation at loads of Lagging p.f

0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.80.20.40.60.8

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Model graph1) Efficiency 2) Regulation

Result:

Ex. No: 6Date:

Predetermination of Regulation of Three Phase Alternator by EMF and MMF Methods

AIM:

To predetermine the regulation of three phase alternator by EMF and MMF methods at various loadsby conducting O.C and S.C tests.

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Name plate details:

3 Alternator DC Shunt Motor

Fuse rating:

125 % of current (Full load current)For dc shunt motor.For alternator

Apparatus required:

Sl. no Description Type Range Quantity

Formulae used:Emf method:A.C Armature resistance Rac = 1.4 Rdc where - Rdc is the resistance in DC supply.Synchronous impedance Zs = Open circuit voltage (E1 (ph))/short circuit current (Isc)Synchronous impedance Xs = (Zs2-Ra2)Open circuit voltage Eo = ((Vrated cos + Ia Ra) 2 + (Vrated sin +IaXs)2) (For lagging power

factor)

Open circuit voltage Eo = ((Vrated cos + Ia Ra)2+(Vrated sin - IaXs)2) (For leading power factor)

Open circuit voltage Eo = ((Vrated cos + Ia Ra)2+( IaXs)2) (For unity power factor)Percentage regulation = ((Eo-Vrated) /Vrated)*100(For both EMF and MMF methods)

Precaution:i. The motor field rheostat should be kept in the minimum resistance position.

ii. The alternator field potential divider should be in the minimum voltage position.iii. Initially all switches are in open position.

Experimental Procedure for both E.M.F and MMF method:

1. Note down the nameplate details of motor and alternator.2. Connections are made as per the circuit diagram.3. Give the supply by closing the dust switch.

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4. Using the three point starter, start the motor to run at the synchronous speed by varying the motor filed rheostat.

5. Conduct an open circuit test by varying the potential divider for various values of field current and tabulate the corresponding open circuit voltage readings.

6. Conduct a short circuit test by closing the TPST switch and adjust the potential divider to set the rated armature current, tabulate the corresponding field current.

7. Conduct a stator resistance test (Measurement of Armature D.C resistance per phase.) and calculate the Armature A.C resistance per phase.

Procedure to draw the graph for EMF method:

1. Draw the open circuit characteristics curve (generator voltage per phase Vs field current)2. Draw the short circuit characteristics curve (short circuit current Vs field current)3. From the graph find the open circuit voltage per phase (E1 (ph)) for the rated short circuit

current (Isc).4. By using respective formulae find the Zs, Xs, Eo and percentage regulation.

CIRCUIT DIAGRAM FOR O.C AND S.C TESTSON 3 PHASE ALTERNATOR:

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Open circuit test:

S.NO Field current(If) Open circuit line voltage (VOL)

Open circuit phase voltage (Vo(ph))

Amps Volts Volts

Short circuit test:

Tabulation to find out the armature resistance (Rdc):

Procedure to draw the graph for MMF method:

1. Draw the open circuit characteristics curve (generator voltage per phase Vs field current)

2. Draw the short circuit characteristics curve (short circuit current Vs field current)3. Draw the line OL to represent If’ which gives the rated generated voltage (V).4. Draw the line LA at an angle (90Φ) to represent If” which gives the rated full

load current.(Isc) on short circuit [(90Φ) for lagging power factor and (90- Φ) for leading power factor].

5. Join the points O and A and find the field current (If) measuring the distance OA that gives the open circuit voltage (E0) from the open circuit characteristics.

6. Find the percentage regulation by using suitable formula.

MODEL CALCULATION:

34

S.NoField current(If)

Short Circuit Current

(Isc)Amps Amps

S.NoArmature current

(I)Armature voltage

(V)Armature Resistance

Ra=V/IAmps Volts Ohms


II YEAR

FOR EMF METHOD& MMF METHODS (Two separate Tables)

Observations of % Voltage Regulation Values at Various Load Conditions:

Load Factor (X)

% Voltage Regulation at Various Power FactorsLagging UPF Leading0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8

X= 0.25X= 0.5X= 0.75X= 1.0

MODEL GRAPH ( FOR BOTH E.M.F &M.M.F METHODS)

RESULT

Expt.no 7Date:

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V & INVERTED V CURVES OF THREE PHASE SYNCHRONOUS MOTOR

AIM:To plot the V and Inverted V- Curves of the given Synchronous Motor at no-load and on load.NAME PLATE DETAILS:

FUSE RATING AND RANGE FIXING:

EQUIPMENTS REQUIRED:

SL NONAME OF THE

EQUIPMENTS/INSTRUMENTSTYPE RANGE

QUANTIT

Y

PRECUTIONS:1. Before giving the three phase supply, the three phase variac must be kept at its minimum position. 2. Before providing d.c. supply to the field regulator of the motor, the field regulator should be kept at minimum position and the field winding should be kept in open position. 3. Start the synchronous machine preferably at no-load condition.4. During the experiment the field current should not exceed 1.5 times the rated current of the field current and the armature current/ ph (Ia ph) should not exceed 1.25 times the rated armature current.

PROCEDURE:1. Make connections as per the circuit diagram.2. Keeping the field circuit of the synchronous motor open, close the TPST switch and vary the auto transformer to obtain the rated three phase voltage. The machine will run at a speed lesser than the synchronous speed. (with the help of damper windings as induction motor)3. Connect the field terminals of the synchronous motor to the d.c. supply by closing the DPST switch and excite the field system. The machine will now begin to run at synchronous speed by establishing magnetic locking between armature circuit and the

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field system. Note down the field current, the corresponding armature current, line voltage and wattmeter readings.4. Vary the field current by adjusting the field excitation system and for each value of field current (from low value of field current up to 1.5 times the rated field current) and note down the corresponding meter readings.5. Repeat the same procedure for various loading conditions carefully not exceeding 1.25 times the armature current and 1.5 times the rated field current.

Circuit Diagram:

TABULATION:At N= Ns (constant) VL = Vrated

Sl. NO

. Load

Field Current If (A)

Armature

Current (A)

W1OBS W1ACT W2obs W2act

Power W=

W1+W2

Power Factor = W/

(√3 * VL

* IL)

Model graph:

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MODEL CALCULATION:

RESULT:

Thus the V and Inverted V-curves of the given synchronous motor have been plotted at various values of loads.

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Ex. No: 8Date:

Load Test on Three Phase Squirrel cage Induction MotorAim:

To conduct the load test on three phase squirrel cage induction motor and to draw the performance characteristics curves.

Name plate details:

3 Induction Motor Auto Transformer

Fuse rating: 125% of rated current (Full load current)

Apparatus required:

Formulae used:

1. Torque = (S1S2) (R+t/2) x 9, 81 N-m. S1, S2 – spring balance readings in Kg. R – Radius of the brake d5rum in m. T – Thickness of the belt in m.

2. Output power = 2NT/60 Watts N – Rotor speed in rpm.

T – Torque in N-m.3. Input power = (W1+W2) Watts

W1, W2 – Wattmeter readings in watts.4. Percentage of efficiency = (Output power/Input power) x 100%5. Percentage of slip = (Ns – N)/Ns x 100%

Ns – Synchronous speed in rpm. N – Speed of the motor in rpm.

6. Power factor (Cos ) = (W1+W2)/3 VLIL.

Circuit diagram

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S.No Name of the Apparatus Type Range qty

1.2.34


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i. The motor should be started without any load

PROCEDURE:

1. Connections are made as per the circuit diagram.2. The TPSTS is closed and the motor is started

using Auto transformer starter to run at rated Voltage.3. At no load the speed, current, voltage and power

are noted.4. By applying the load, for various values of current

the above-mentioned readings are noted.5. The load is later released and the motor is

switched off and the graph is drawn.

OBSERVATION:Circumference of the brake drum =

Thickness of the belt =

MODELGRAPH:The graph drawn for Output power Vs speedOutput power Vs line currentOutput power vs. TorqueOutput power Vs power factorOutput power Vs EfficiencyOutput power Vs %slip.

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MODEL GRAPH

TABULATION FOR LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTORMultiplication factors for wattmeters: …………..

S. no

Load current

(IL)

Load voltag

e(VL)

Input power (W1) Input power (W2) Speed of

the motor (N)

Spring balance reading

Torque (T) =

(s1~s2)* (R)* (9.81)

Output power 2NT/

60

Efficiency ()=

o/p / i/p x 100

Slip (S)= {(Ns-N)

/ Ns} x 100

Power factor (cos)

=i/p / VLIL

Observed

Actual

Observed

Actual S1 S2S1~S2 % %

Amps Volts WattsWatt

sWatts Watts rpm Kg Kg Kg N-m Watts

MODEL CALCULATION:

RESULT:

Ex. No: 9

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Date:

SPEED CONTROL OF THREE PHASE SLIP RING INDUCTION MOTOR

AIM: To conduct the speed control test on three phase slip ring induction motor.

APPARATUS REQUIRED:

PROCEDURE1. Connections are made as per the circuit diagram.2. Note down the resistance in each phase using Multimeter.3. Switch ON the A.C power supply.4. Then the speed of the motor is taken for each resistance per phase.5. The graph was drawn between resistance and speed.

THEORYThese motors are practically started with full line voltage applied across the stator

terminals, the value of starting current is adjusted by introducing the variable resistance in the rotor circuit. The controlling resistance is in the resistance being gradually cut out of the rotor circuit, as the motor attains rated speed. It has been already shown that by decreasing rotor resistance, the motor attains rated speed and at the same time the starting torque is also increased due to improvement in power factor.

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TABULAR COLUMN:Sl.no Rotor resistance

(Position Or Value)Speed in Rpm

Model graph

RESULT

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Expt N0 : 10Date:

LOAD TEST ON CAPACITOR START INDUCTION RUN SINGLE PHASE INDUCTION MOTOR

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:

EQUIPMENTS REQUIRED:

SL NONAME OF THE

EQUIPMENTS/INSTRUMENTSTYPE RANGE

QUANTIT

Y

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CIRCUIT DIAGRAM :

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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)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.

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

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6. 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

8. 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. No.

VL (V)

IL

(A)Speed(rpm)

I/P Power (W)

Spring Balance reading

Torque(Nm)

O/PPower (W)

%slip %η cosφ

Obs Act S1 S2 S1~S2

MODEL CALCULATIONS:

RESULT:

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

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Expt No: 11 Date

STUDY OF D.C & A.C MOTOR STARTERS

AIM:

To study the different kinds of D.C &A.C motor starters

EQUIPMENT REQUIRED:

THEORY :

The value of the armature current in a D.C shunt motor is given by

Ia = ( V – Eb )/ RaWhere V = applied voltage. Ra = armature resistance. E b = Back .e.m.f .

In practice the value of the armature resistance is of the order of 1 ohms and at the instant of starting the value of the back e.m.f is zero volts. Therefore under starting conditions the value of the armature current is very high. This high inrush current at the time of starting may damage the motor. To protect the motor from such dangerous current the D.C motors are always started using starters.The types of D.C motor starters arei) Two point starters ii) Three point starters iii) Four point starters.The functions of the starters are i) It protects the from dangerous high speed.ii) It protects the motor from overloads.

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Sl No. Name of the apparatus Quantity

1 Two Point starter 12 Three Point starter 13 Four Point starter 14 DOL Starter 15 Auto transformer Starter 16 Star-Delta Starter 17 Rotor Resistance Starter 1


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i) TWO POINT STARTERS: ( refer fig 1)It is used for starting D.C. series motors which has the problem of over speeding

due to the loss of load from its shaft. Here for starting the motor the control arm is moved in clock-wise direction from its OFF position to the ON position against the spring tension. The control arm is held in the ON position by the electromagnet E. The exciting coil of the hold-on electromagnet E is connected in series with the armature circuit. If the motor loses its load, current decreases and hence the strength of the electromagnet also decreases. The control arm returns to the OFF position due to the spring tension, Thus preventing the motor from over speeding. The starter also returns to the OFF position

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when the supply voltage decreases appreciably. L and F are the two points of the starter which are connected with the motor terminals

ii) THREE POINT STARTER: ( refer fig 2 )

It is used for starting the shunt or compound motor. The coil of the hold on electromagnet E is connected in series with the shunt field coil. In the case of disconnection in the field circuit the control arm will return to its OFF position due to spring tension. This is necessary because the shunt motor will over speed if it loses excitation. The starter also returns to the OFF position in case of low voltage supply or complete failure of the supply. This protection is therefore is called No Volt Release ( NVR). Over load protection:

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When the motor is over loaded it draws a heavy current. This heavy current also flows through the exciting coil of the over load electromagnet ( OLR). The electromagnet then pulls an iron piece upwar6.ds which short circuits the coils of the NVR coil. The hold on magnet gets de-energized and therefore the starter arm returns to the OFF position, thus protecting the motor against overload. L, A and F are the three terminals of the three point starter.

iii) FOUR POINT STARTER:

The connection diagram of the four point starter is shown in fig 3. In a four point starter arm touches the starting resistance, the current from the supply is divided into three paths. One through the starting resistance and the armature, one through the field circuit, and one through the NVR coil. A protective resistance is connected in series with the NVR coil. Since in a four point starter the NVR coil is independent of the of the field ckt connection , the d.c motor may over speed if there is a break in the field circuit. A D.C motor can be stopped by opening the main switch. The steps of the starting resistance are so designed that the armature current will remain within the certain limits and will not change the torque developed by the motor to a great extent.

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STUDY OF INDUCTION MOTOR STARTERS

AUTO –TRANSFORMER STARTING

An auto transformer starter consists of an auto transformer and a switch as shown in the fig. When the switch S is put on START position, a reduced voltage is applied across the motor terminals. When the motor picks up speed, say to 80 per cent of its mornal speed, the switch is put to RUN position. Then the auto-transformer is cut out of the circuit and full rated voltage gets applied across the motor terminals.(Ref. To text book for fig)The circuit dia in the fig is for a manual auto-transformer starter. This can be made push button operated automatic controlled starter so that the contacts switch over from start to run position as the motor speed picks up to 80% of its speed. Over-load protection relay has not been shown in the figure. The switch S is air-break type for small motors and oil break type for large motors. Auto transformer may have more than one tapping to enable the user select any suitable starting voltage depending upon the conditions.Series resistors or reactors can be used to cause voltage drop in them and thereby allow low voltage to be applied across the motor terminals at starting. These are cut out of the circuit as the motor picks up speed.

STAR- DELTA METHOD OF STARTING:

The startor phase windings are first connected in star and full voltage is connected across its free terminals. As the motor picks up speed, the windings are disconnected through a switch and they are reconnected in delta across the supply terminals. The current drawn by the motor from the lines is reduced to as compared to the current it would have drawn if connected in delta.The motor windings, first in star and then in delta the line current drawn by the motor at starting is reduced to one third as compared to starting current with the windings delta-connected.In making connections for star-delta starting, care should be taken such that sequence of supply connections to the winding terminals does not change while changing from star connection to delta connection. Otherwise the motor will start rotating in the opposite direction, when connections are changed from star to delta. Star-delta starters are available for manual operation using push button control. An automatic star – delta starter used time delay relays(T.D.R) through which star to delta connections take place automatically with some pre-fixed time delay. The delay time of the T.D.R is fixed keeping in view the starting time of the motor.(Ref. To text book for fig)

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FULL VOLTAGE OR DIRECT –ON-LINE STARTING

When full voltage is connected across the stator terminals of an induction motor, large current is drawn by the windings. This is because, at starting the induction motor behaves as a short circuited transformer with its secondary, i.e. the rotor separated from the primary, i.e. the stator by a small air-gap.

At starting when the rotor is at standstill, emf is induced in the rotor circuit exactly similar to the emf induced in the secondary winding of a transformer. This induced emf of the rotor will circulate a very large current through its windings. The primary will draw very large current from the supply mains to balance the rotor ampere-turns. To limit the stator and rotor currents at starting to a safe value, it may be necessary to reduce the stator supply voltage to a low value. If induction motors are started direct-on-line such a heavy starting current of short duration may not cause harm to the motor since the construction of induction motors are rugged. Other motors and equipment connected to the supply lines will receive reduced voltage. In industrial installations, however, if a number of large motors are started by this method, the voltage drop will be very high and may be really objectionable for the other types of loads connected to the system. The amount of voltage drop will not only be dependent on the size of the motor but also on factors like the capacity of the power supply system, the size and length of the line leading to the motors etc. Indian Electricity Rule restricts direct on line starting of 3 phase induction motors above 5 hp.

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RESULT:

Thus the construction and working of different starters for starting D.C series, shunt, compound and three phase induction motors are studied.

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VIVA questions for the Experiments

1) LOAD TEST ON DC SHUNT AND SERIES MOTORS

1. What is the need for a starter?2. Name the different types of starters for DC motors.3. Why a DC shunt motor is called a constant Speed motor?4. State few applications of DC shunt series motor.5. What is the role of commutator in a DC motor?6. What is the effect of armature reaction on the performance of DC motor?7. What happen when the field circuit gets opened when a DC shunt motor is running?8. How to reverse the direction of rotation of DC motor?9. Explain why D.C series motor are started under no load.

2) OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR

1. Define critical field resistance and critical speed. 2. State the conditions to be satisfied by a DC shunt generator to build-up voltage. 3. What is residual flux and what happens to the generator induces EMF when residual flux is zero? 4. What is the purpose of SPST switch connected in the field circuit of the generator? 5. Why the speed must be maintained constant throughout the experiment?

LOAD TEST ON SELF EXCITED DC SHUNT GENERATOR1. What is a prime mover?2. Why the speed of generator should be maintained constant during the experiment?3. Why does the terminal voltage fall as the load on the generator is increased?4. What is armature reaction and what are its effects on the performance of DC generator?

3) SPEED CONTROL OF DC SHUNT MOTOR1. Which method of speed control is used for controlling the speed of the motor above its rated speed? Give reason.2. Which method of speed control is used for controlling the speed of the motor below its rated speed? Give reason.3. Explain the reasons for the shape of the graphs obtained.4. State any method to control the speed of a D.C series motor?

4) LOAD TEST ON A SINGLE PHASE TRANSFORMER1. 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?

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5. What is the effect of change in frequency on the efficiency of the transformer?

5) O.C AND S.C TESTS ON A SINGLE PHASE TRANSFORMER1. Why O.C test is conducted on the L.V side and S.C test on the H.V side?2. Define regulation in a transformer.3. Why the regulation graph is not passing through the origin?4. State the condition for maximum efficiency?5. What is the regulation of an Ideal transformer?6. What is the condition for maximum efficiency of a transformer?

6) PREDETERMINATION OF REGULATION BY EMF& MMF METHOD

1. Define regulation.2. What is meant by pessimistic method?3. Which method is called as optimistic method?4. What are the advantages of EMF and MMF method?5. Name some other methods used to predetermine the regulation.

7) V & INVERTED V CURVES ON 3 PHASE SYNCHRONOUS MOTOR1) How will you start a synchronous motor?2) What are the uses of Damper windings?3) What is meant my synchronization?4) Define pull in torque.5) Define pull out torque.6) Define synchronous speed.

8) LOAD TEST ON SQUIRREL CAGE INDUCTION MOTOR1) What is squirrel cage induction motor?2) What is the normal range of no load current of an induction motor?3) Distinguish between rotating transformer and static transformer?4) Define slip.5) Draw the torque- slip Characteristics of an Induction motor.

9) SPPED CONTROL OF 3 PHASE SLIP RING INDUCTION MOTOR1) What is meant by slip ring?2) What are the different methods of seed control in slip ring induction motor?3) What are the advantages of using rotor resistance starter?4) Explain the basic speed control equation of a.c machines.5) Compare squirrel cage motors with slip ring motors.

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10) LOAD TEST ON SINGLE PHASE INDUCTION MOTOR

VIVA QUESTIONS:1. What are the different types of single phase induction motors?2. Explain why single phase induction motors are not self-starting?3. Draw the phasor diagrams of Single phase induction motor indicating the starting

winding and running winding current components.4. Define slip.5. List out the applications of Single Phase induction motors.

11) STUDY OF D.C MOTOR STARTERS

VIVA QUESTIONS:

1. Differentiate two point and three point starter2. What is the need for starter in electrical technology?3. Differentiate four point and three point starter4. What are the types of starter?5. What are the protective devices used in starters?


VIVA QUESTIONS:

1. Differentiate star – delta and auto transformer starter2. What is the need for starter in electrical technology?3. Differentiate auto transformer and DOL starter4. What are the types of AC starters?5. What are the protective features used in starters?

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Introduction to Experiments

(1) LOAD TEST ON DC SHUNT & SERIES MOTORS

INTRODUCTIOND.C motor converts electrical energy into mechanical energy (rotational) with the

help of the excitation. In this experiment the effect of mechanical loading on torque, speed, Output power, line current and efficiency can be understood

(2) OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR

INTRODUCTION In this experiment D.C motor acts as prime mover supplying mechanical energy which is converted into electrical energy by the D.C shunt generator, with the help of field system of generator

Open circuit characteristics give the relation between the excitation and generated voltage (e.m.f). Role of residual flux, critical resistance and voltage building up processes can be understood by this experiment.

LOAD TEST ON SELF EXCITED DC SHUNT GENERATOR

INTRODUCTIONIn this experiment, the effect of armature resistance and armature reaction can be

understood. Internal characteristics explain the effect of armature reaction and external characteristics help in understanding the effect of armature resistive voltage drop in addition to armature reaction.

(3) SPEED CONTROL OF DC SHUNT MOTORINTRODUCTIONThis experiment helps in understanding

(1) the effect of back e.m.f on speed, at constant excitation(Armature control method)

(2) the effect of field current( before saturation) on speed, at consant armature voltage(Field control method)

(4) LOAD TEST ON A SINGLE PHASE TRANSFORMER

INTRODUCTIONThis experiment helps in understanding the performance of single phase

transformer, which is an electromagnetic device working on the principle of electromagnetic induction (Statically induced e.m.f which is on the self and mutual induction basis.)

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(5) O.C AND S.C TESTS ON A SINGLE PHASE TRANSFORMER

INTRODUCTIONOpen circuit test is helpful in measuring the core losses (constant losses).Short circuit test is useful in measuring the copper losses (electrical losses) at

rated load condition.With the help of these tests and measurements, the performance of the

transformer at different load conditions can be predetermined.

(6) PREDETERMINATION OF REGULATION BY EMFAND MMF METHOD

INTRODUCTIONArmature resistance measurement, Open circuit and short circuit tests are

conducted on alternators/synchronous generators to estimate the resistance, impedance and reactance per phase of the armature winding.

Open circuit test is helpful in measuring the core losses (constant losses).Short circuit test is useful in measuring the copper losses (electrical losses) at

rated load condition.With the help of these tests, characteristic curves and measurements, the

performance of the alternator/synchronous generator, at different load conditions can be predetermined.

7) V AND INVERTED V CURVES OF THREE PHASE SYNCHRONOUS MOTOR

INTRODUCTIONInitially the motor starts as induction motor with the help of damper winding and

with the field kept open. When the speed approaches near synchronous speed, the motor field is excited

and thus the motor is brought into magnetic locking.V Curves explain the relationship between field current and armature currentInverted v curves explain the relationship between field current and power factor

of the motor circuit.

(8) LOAD TEST ON SQUIRREL CAGE INDUCTION MOTOR

INTRODUCTIONInduction motor converts electrical energy into mechanical energy(rotational)

(supply provided to the stator winding itself acts as excitation /aiding mechanism, as per Lenz law and Faraday’s laws of electromagnetic induction)

In this experiment the effect of mechanical loading on torque, speed, output power, power factor, line current and efficiency can be understood.

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(9) SPEED CONTROL OF THREE PHASE SLIP RING INDUCTION MOTOR

INTRODUCTIONInduction motor speed control can be done from stator and rotor side.In the stator side control methods either the net voltage fed into the stator winding

is controlled or its frequency is varied to operate the machine at different speeds.In case of Slip ring Induction motor, rotor side effective resistance can be

controlled through external rotor resistors or through rotor resistance starter and thus, the speed and slip of the motor can be controlled.

10) LOAD TEST ON SINGLE PHASE (CAPACITOR START INDUCTION) RUN INDUCTION MOTOR

INTRODUCTIONInduction motor converts electrical energy into mechanical energy(rotational)

(supply provided to the stator winding itself acts as excitation /aiding mechanism, as per Lenz law and Faraday’s laws of electromagnetic induction).

Single phase induction motors are not self-starting and a revolving double field arrangement effected with the help of (starting winding + main Winding steup) is used to start the motor.

In this experiment, the effect of mechanical loading on torque, speed, output power, power factor, line current and efficiency can be understood.

(11) STUDY OF D.C MOTOR STARTERS

INTRODUCTIONThis study is helpful in understanding the performance of starter and its salient

features like no voltage/over load protection circuitry.


INTRODUCTIONThis study is helpful in understanding the performance of starter and its salient

features like no voltage/over load protection circuitry, thermal over load protection etc. in addition to starting torque developments and starting current limitations.

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Me 2209 Elece Engg Lab for Mech Final