anna university chennai department of mechanical

ELECTRICAL ENGINEERING LAB MANUAL II YEAR

1

ANNA UNIVERSITY CHENNAI

DEPARTMENT OF MECHANICAL ENGINEERING

II YEAR MECH / III SEMESTER

EE 8351- ELECTRICAL ENGINEERING LABORATORY

HOD/EEE LAB INCHARGE

Dr.M.KARTHIKEYAN PROF.S.NATARAJAN/AP/EEE


2

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


3

.

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


4

SYLLABUS

EE8351 – 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.


5

Subject code : EE:8361

Subject Title : Electrical Engineering Lab

Staff name : S.NATARAJAN

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 covered Learning objectives Page

No*

No. of

hours

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

motor

Students will be exposed to the

performance characteristics D.C. shunt

& Series motors.

9

3 hrs.

2

Open circuit and load

characteristics of self-excited D.C.

shunt generator


concepts of Critical resistance(Rc),

O.C.C at the specified speed, External

Characteristics, and Internal

Characteristics.

15

3hrs

3 Speed 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

4 Load 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

5 Open 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


concepts of predetermination of

Voltage regulation by EMF & MMF

methods. Students will be exposed to

30

3hrs


6

the performance characteristics of the

machine

7 V 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

8 Load test on three phase Squirrel

Cage Induction motor


performance characteristics of the

three phase Squirrel Cage Induction

motor.

37

3hrs

9 Speed 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

10 Load test on single phase Induction

motor


performance characteristics of single

phase Induction motor.

42 3hrs

11 Study 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


7

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

EC

No.

Evaluation

Components

Duration Weightage

1 Observation Continuous 20%

2 Record Continuous 30%

3 Attendance Continuous 30%

4 Model lab 3hr 20%


8

LEARNING OBJECTIVES

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.


9

Ex. No: 1.A

Date:

LOAD TEST ON DC SHUNT MOTOR

Aim:

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

curves

Exercise

Draw 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 = )2

(81.9)~( 21

tRSS in N-M

S1, S2 – spring balance readings in Kg

R- Break drum radius in m

(ii) Input power = V x I in Watts

(iii) Output power = 2NT / 60 in Watts


10

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

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.


11

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 balance

Reading

In kg

Input

Power

in

Watts

Torque

in NM

Output

Power

in

Watts

Efficiency

in %

S1 S2 S1S2

MODEL GRAPH

(A) Electrical characteristics

in %

T in N-m

Speed in rpm

IL in Amps

N IL T %

Output power in watts


12

(B) Mechanical characteristics

(C) Torque, Speed Vs Load current

Model calculation:

Graph:

Output Vs η%

Output Vs T

Output Vs N

Output Vs IL

Torque Vs N

Result:

T Vs N

Sp

eed

(N

) in

rpm

Torque ( T ) in N-m

Torq

ue

(T)

in N

-m

Spee

d (

N)

in r

pm

IL Vs N

Load current (IL) in Amps

IL Vs T


13

EXPT. No: 1.B

Date:

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 load

2. 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:


14

TABULAR COLUMN:

MODEL GRAPH:


15

RESULT:

Ex. No: 2

Date:

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

Exercise

1. 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:

in %

T in N-m

Speed in rpm

IL in Amps

N IL T %

Output power in watts


16

Sl.no Description Type Specification Quantity

Formula used:

Generated voltage Eg = VL + Ia Ra

Precautions 1. 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 test

2. 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.


17

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.

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 diagram

2. 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


18

Circuit diagram for find the generator armature resistance [Ra]

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.no Armature voltage

Va in volts

Armature current

Ia in amps Ra = Va/ Ia in ohms

Model graph

Open circuit characteristics

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

If

Field current

[If] in amps

Open

cir

cuit

volt

age

in

Volt

s [E

o]

Eo Vs If


19

Result:

Ex. No: 3

Date:

SPEED CONTROL OF DC SHUNT MOTOR

Aim

To 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

Apparatus Required:


Load current [IL] in amps

Armature current [Ia] in amps

Load

volt

age

in V

olt

s [V

L]

Gen

erat

ed e

mf

in V

olt

s [E

g]

Eg Vs Ia

VL Vs IL


20

Name plate details:

Motor

Speed

Type

Field Armature

Fuse rating calculation:

CIRCUIT DIAGRAM

Precaution:


21

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


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

Tabulation for Armature Control Method

Field current If1 Field current If2

Armature

voltage Va Speed N in RPM

Armature

voltage Va

Speed N in

RPM

Tabulation for Field Control Method

Armature Voltage Va1 Armature Voltage Va2

Field Current If

In AMPS Speed N in RPM

Field Current

If In AMPS

Speed N in

RPM


22

MODEL GRAPH:

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.


23

4.

5.

THEORY:

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.


24

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.

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%

)(.

)(.)(.X

V

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)


25

MODEL CALCULATION:

MODEL GRAPH:

RESULT: -

Ex. No: 5

Date:

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 factor

Exercise

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

Apparatus Required:



26

-

Name plate details:

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 test

10 % of rated primary current

S.C test

125 % of rated secondary current

Formulae Used:

Open circuit test:

1. No load power factor ococ

oc

IV

W

)(cos 0

WOC = open circuit power in watts

VOC = open circuit voltage in volts

IOC = open circuit current in amps

2. No load working component resistance (RO); oOC

OC

OCosI

VR

in ohms

3. No load magnetizing component (XO); oOC

OC

OSinI

VX

in ohms

Short circuit test:

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

SC

OI

VZ 2 in ohms.

5. Equivalent resistance referred to HV side (R02); 22

SC

SCO

I

WR in ohms

6. Equivalent reactance referred to HV side (X02); 2

2

2

22 OOO RZX in ohms

7. Transformation ratio (K); 1

2

V

VK

8. Equivalent resistance referred to LV side (R01); 2

2

1K

RR O

O in ohms


27

9. Equivalent reactance referred to LV side (X01); 2

2

1K

XX O

O in ohms

Efficiency and regulation

10. Output power = )( CosKVAX in watts

11. Chopper loss = )( 2

SCWX in watts

12. Total loss WT = )( lossIronlossCu in watts

13. Efficiency = 100 lossTotalpowerOutput

powerOutputin %

14. Regulation = 100[

2

22

O

OOSC

V

SinXCosRIX 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)


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)


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


28

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 volts Observed Actual


29

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 Amps Observed 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) =

.

Fractio

n of

load/

Load

factor

(X)

Output power

1000* )( CosKVAX

in watts at Various P.F

Copper loss

at various

loads

)( 2

SCWX

in watts

Total loss

in watts WT=

(Woc ) +(X2

*Wsc)

Efficiency at Various P.F

TWpo

po

/

/

* (100 ) in %

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1

¼

½

¾

1

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


30

0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8

0.2

0.4

0.6

0.8

Model graph

1) Efficiency 2) Regulation

Result:

Ex. No: 6

Date:

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


31

AIM:

To predetermine the regulation of three phase alternator by EMF and MMF methods at

various loadsby conducting O.C and S.C tests.

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-Ra

2)

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.


32

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.


3. Give the supply by closing the dust switch.

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:


33

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.

S.No Field current(If)

Short Circuit Current

(Isc)

Amps Amps

S.No Armature current

(I)

Armature voltage

(V)

Armature Resistance

Ra=V/I

Amps Volts Ohms


34

MODEL CALCULATION:

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 Factors

Lagging UPF Leading

0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8

X= 0.25

X= 0.5

X= 0.75

X= 1.0

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

RESULT


35

Expt.no 7

Date:

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 NO NAME OF THE

EQUIPMENTS/INSTRUMENTS TYPE RANGE

QUANTITY

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


36

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

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 W2ac

t

Power W=

W1+W2

Power Factor = W/ (√3 *

VL * IL)


37

Model graph:

MODEL CALCULATION:

RESULT:

Thus the V and Inverted V-curves of the given synchronous motor have been plotted at

various values of loads.


38

Ex. No: 8

Date:

Load Test on Three Phase Squirrel cage Induction Motor Aim:

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.

S.No Name of the Apparatus Type Range qty

1.

2.

3

4


39

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

i. The motor should be started without any load

PROCEDURE:


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:


40

The graph drawn for

Output power Vs speed

Output power Vs line current

Output power vs. Torque

Output power Vs power factor

Output power Vs Efficiency

Output power Vs %slip.

MODEL GRAPH

TABULATION FOR LOAD TEST ON THREE PHASE SQUIRREL CAGE

INDUCTION MOTOR

Multiplication factors for wattmeters: …………..

S.

no

Load

current

(IL)

Load

voltage

(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

Efficienc

y ()= o/p / i/p

x 100

Slip (S)= {(Ns-N)

/ Ns}

x 100 Power factor

(cos)

= i/p / VLIL

Observe

d

Actu

al

Observ

ed Actual S1 S2

S1

~ S2 % %

Amps Volts Watts Watt

s Watts Watts rpm Kg Kg Kg N-m Watts


41

MODEL CALCULATION:

RESULT:

Ex. No: 9

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:

PROCEDURE


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.

THEORY

These 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.


42

TABULAR COLUMN:

Sl.no Rotor resistance

(Position Or Value)

Speed in Rpm

Model graph

RESULT


43

Expt N0 : 10

Date:

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 NO NAME OF THE

EQUIPMENTS/INSTRUMENTS TYPE RANGE

QUANTITY


44

CIRCUIT DIAGRAM :


45


46

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)


47

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/P

Power

(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.


48

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 )/ Ra

Where 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 are

i) 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.

Sl No. Name of the apparatus Quantit

y

1 Two Point starter 1

2 Three Point starter 1

3 Four Point starter 1

4 DOL Starter 1

5 Auto transformer Starter 1

6 Star-Delta Starter 1

7 Rotor Resistance Starter 1


49

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

when the supply voltage decreases appreciably. L and F are the two points of the starter

which are connected with the motor terminals


50

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:

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


51

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.


52

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)


53

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.


54


55

RESULT:

Thus the construction and working of different starters for starting D.C series,

shunt, compound and three phase induction motors are studied.


56

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 GENERATOR

1. 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 MOTOR

1. 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 TRANSFORMER

1. Define Regulation of a Transformer.

2. What is the effect of load p.f on regulation of Transformer?

3. What is the condition for maximum efficiency?

4. Determine the percentage load at which maximum efficiency occurred for the given

single-phase transformer?

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


57

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

1. 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 MOTOR

1) 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 MOTOR

1) 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 MOTOR

1) 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.


58

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 starter

2. What is the need for starter in electrical technology?

3. Differentiate four point and three point starter

4. What are the types of starter?

5. What are the protective devices used in starters?


VIVA QUESTIONS:

1. Differentiate star – delta and auto transformer starter

2. What is the need for starter in electrical technology?

3. Differentiate auto transformer and DOL starter

4. What are the types of AC starters?

5. What are the protective features used in starters?


59

Introduction to Experiments

(1) LOAD TEST ON DC SHUNT & SERIES MOTORS

INTRODUCTION

D.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

INTRODUCTION

In 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 MOTOR

INTRODUCTION

This 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

INTRODUCTION

This 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.)

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


60

INTRODUCTION

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 and measurements, the performance of the

transformer at different load conditions can be predetermined.

(6) PREDETERMINATION OF REGULATION BY EMFAND MMF METHOD

INTRODUCTION

Armature 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

INTRODUCTION

Initially 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 current

Inverted v curves explain the relationship between field current and power factor

of the motor circuit.

(8) LOAD TEST ON SQUIRREL CAGE INDUCTION MOTOR

INTRODUCTION Induction 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.


61

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

INTRODUCTION

Induction 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

INTRODUCTION Induction 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

INTRODUCTION

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

features like no voltage/over load protection circuitry.


INTRODUCTION

This 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.

*********************************************************************

anna university chennai department of mechanical

Documents