Eee(Me)Lab Manual

8/10/2019 Eee(Me)Lab Manual

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Dept of EEEGNIT

MAGNETIZATION

CHARACTERISTICS OF A

D.C. SHUNT GENERATOR

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Experiment no: 2

MAGNETIZATION CHARACTERISTICS OF

A D.C. SHUNT GENERATOR

AIM : To obtain the Magnetization Characteristics of a D.C. Shunt Generator and to determine

its Critical field resistance & Critical speed.

NAME PLATE DETAILS:

Tpe DC S!"nt Motor DC S!"nt Gener#tor

R#tin$% &.'HP 2 ()

*o+t% 22' * DC 22' * DC

C"rrent ,2 A ,2 A

Ex-. *o+t% 22' * DC 22' * DC

Ex-. C"rrent '. A './ A

D"t S , S , In%. C+#%% 0 0

Spee1 ,'' rpm ,'' rpm

APPARATUS:

S.No App#r#t"% Re3"ire1 R#tin$ Tpe 4t

', *o+tmeter 5'6&''7* M.C ,

'2 Ammeter 5'6,7A M.C ,

'& R!eo%t#t &' o!m8,.2A 6 &

'9 R!eo%t#t &' o!m8,.2A 6' T#-!ometer 6 Di$it#+ ,

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THEOR:

I7 M#$neti;#tion C!#r#-teri%ti-%

The magnetization characteristics shows the relation between the no load generated emf

in armature, E and the field !or" e#citing current, $f at a gi%en fi#ed speed as shown in

model graph. These characteristics are also nown as the 'o load saturation characteristics or (pen

circuit characteristics. The shape of these characteristics is practicall) same for all

generators whether separatel) e#cited or self e#cited Due to the residual magnetism in the poles, some emf is generated e%en when $f *

represented b) (D++. ence, the cur%e starts a little wa) up. The slight cur%ature, DE++ at the lower end is due to magnetic inertia. $t is seen that the

first part of the cur%e, EC++ is practicall) straight. This is due to the fact that at low flu#

densities, reluctance of iron path being negligible !due to high permeabilit)", total

reluctance is gi%en b) the air gap reluctance, which is constant. ence, the flu# and

conse-uentiall) the generated emf are directl) proportional to the e#citing current. ow e%er at high flu# densities, where m is small, iron path reluctance becomes

appreciable and straight relation, C++ between Eo and $f no longer holds good, i.e.,

saturation of poles start.

!++ refers to the model graph"

II7 Criti-#+ re%i%t#n-e

$t is that ma#imum %alue of the field resistance, abo%e which the machine fails to e#cite

i.e. there will be no build up of the %oltage. This resistance corresponds to the straight/line position of the magnetization

characteristic because the magnetic circuit does not offer an) appreciable reluctance to

the magnetic flu#.

III7 Criti-#+ %pee1

$t is that speed for which the gi%en shunt field resistance will represent critical field

resistance5OR7$t is that minimum %alue of the speed of the machine below which the machine fails

to e#cite .

PROCEDURE:

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0. Connect the circuit as per the circuit diagram.

1. $nitiall) the starter must be in ( & S2ST Switch in open positions.

3. Switch on the D.C. Motor to 114 D.C. Suppl) b) closing the D2ST Switch.

5. Start the D.C. motor using the three point starter and thereb) ad6ust the speed of it to the rated

speed of the D.C.generator using field method of speed control.

7. 'ote down the %oltage of the %oltmeter which represents the residual %oltage of the generator

when S2ST switch is in open condition.

8. E#cite the field winding D.C.generator in steps b) decreasing its e#ternal resistance graduall)

and note down %arious corresponding readings of ammeter and %oltmeter till 0.0 to 0.17 times

the rated %oltage of the generator is reached, maintaining constant speed .

9. Graduall) reduce the field current of generator and mae it to zero finall) b) opening S2ST

switch. and disconnect the D.C. Motor from the 114 D.C. Suppl)

.

O0SER*ATION TA0LE:

At -on%t#nt %pee1 o< ,''r.p.m.

S.NoFie+1 C"rrent A Arm#t"re *o+t#$e *

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MODEL GRAPHS:

CALCULATIONS:

TO FIND CRITICAL FIELD RESISTANCE:

0. 2lot the magnetization cur%e.

1. Draw the tangent such that it touches most of the linear part of the cur%e. This line is the

Critical field resistance line.

3. The slope of the abo%e line gi%es the Critical field resistance.

TO FIND CRITICAL SPEED:

0. Draw the constant field resistance line ;f .1. rom point draw a line on to the Critical field resistance line.

'ow the Critical speed, 'c * !


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PRECAUTIONS:6

0. The field rheostat of the motor must be ept in minimum & for the generator in

ma#imum positions before switching on the D.C. suppl).

1. Ensure that the starter arm is at e#treme left position.

3.


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SPEED CONTROL OF

D.C. SHUNT MACHINE

Experiment no: &

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SPEED CONTROL OF DC SHUNT MACHINE

AIM : Determination of the speed characteristics of DC shunt machine b) a" ield control b"


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THEOR:

Speed control of DC shunt motor can be done in the following two wa)s ield control

method

Armature control method:-

This method is used when speeds below the no load speed are re-uired.


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Therefore at constant flu# !field current", as the %oltage across the armature increases, the speed

of the motor also increases and %ice %ersa.

PROCEDURE:

0. Connect the circuit as shown in the circuit diagram.

1. eep the armature rheostat resistance at ma#imum position and the field rheostat at minimum

position before starting the e#periment.

3. The DC suppl) is switched (' and motor is started with the help of a three point starter.

5. eep the field current constant and %ar) the rheostat in series with the armature.

7. 'ote down the corresponding readings of the %oltmeter across the armature and speed of the

DC shunt motor.

8. 'ow the rheostat of the armature is ept as it is and now the field rheostat is %aried and note

down the corresponding readings of field current and the speed of the DC shunt motor.

O0SER*ATION TA0LES:

FIELD CONTROL METHOD

At *# >

Spee1 N 5rpm7

ARMATURE CONTROL METHOD


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MODEL GRAPHS:

$ED C('T;( MET(D


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PRECAUTIONS:6

0. The field rheostat of the motor must be ept in minimum before switching on the 114 D.C

suppl).


3.


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S)IN0URNEBS TEST

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Experiment no: 9

S)IN0URNEBS TEST

AIM : To 2re/determine the efficienc) and performance characteristics of a DC Shunt machine.

!both as a generator & motor".

NAME PLATE DETAILS:

S.No Tpe DC S!"nt Motor

', R#tin$% &.'HP

'2 *o+t% 22' * DC

'& C"rrent ,2 A

'9 Ex-. *o+t% 22' * DC

' Ex-. C"rrent '. A

' D"t S ,

'/ In%. C+#%% 0

'= Spee1 ,'' rpm

APPARATUS:


', *o+tmeter 5'6&''7 M.C ,

'2 Ammeter 5'6,'7 M.C ,

'& Ammeter 5'67 M.C 2

'9 R!eo%t#t &' O!m 8 ,.2 A M.C ,

' T#-!ometer Di$it#+ ,

' F"%e 2' 2

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THEOR:

S)IN0URNEBS TEST:6

$t is a simple method in which losses are measured separatel) and from their nowledge,

efficienc) at an) load can be pre/determined in ad%ance. The onl)running test needed is

a no load test. Swinburne s test is applicable to those machines in which flu# is practicall) constant i.e.

Shunt wound and Compound wound machines. The machine is running as a motor on no/load at its rated %oltage and its speed be

ad6usted to its rated %alue using Shunt regulator. The no/load armature current $ao is measured using an ammeter, where as shunt field

current $sh is gi%en b) another ammeter. The no/load input current is gi%en b)

Io > I#o I%!

et the suppl) %oltage be 4 %olts

'o/load input * 4 $o watts

2ower input to armature * 4 $ao watts

2ower input to shunt * 4 $sh watts

'o/load input supplies Copper losses !


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Pre1etermin#tion o< e !(utput Total losses"

!Efficienc)"# * !# (utput" > !# output Ac ! # $ $sh"H ;a"

I ma) be J, K, L, full load !0"

Ma#imum Efficienc) condition : 4ariable losses !$aH ;a" * Constant losses ! Ac"

PROCEDURE:

0. Connect the circuit as per the Circuit diagram.

1. $nitiall) the starter must be in off position.


5. Start the D.C. motor using the three point starter and thereb) ad6ust the speed to its rated speed

using field rheostat.13

7. 'ote down the readings of 4oltmeter & * Io I#o R# )#tt% > )#tt%

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CALCULATION TA0LE:

I7 For Motor

S.No Inp"t*o+t#$e

5*7

Inp"tC"rrent

5I7

Fie+1C"rrent

5I%!7

Arm#t"reCopper

Lo%%e%

Tot#+Lo%%e%

Inp"tPoer

For Gener#tor

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S.No O"tp"t*o+t#$e

5*7

O"tp"tC"rrent

5I7

Fie+1C"rrent

5I%!7

Arm#t"reCopper

Lo%%e%

Tot#+Lo%%e%

Inp"tPoer

MODEL GRAPHS:

S)IN0URNEBS TEST

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PRECAUTIONS:6

0. The field rheostat of the motor must be ept in minimum before switching on the 114 D.C

suppl).


3.


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1. Ahat are the ad%antages & disad%antages of this testB

3. Ah) this test is not suitable for D.C series motorB

5. Ahat is the purpose of 3 point starterB

7. Ahat happens if field is open in D.C motorB

8. ow do )ou reduce the iron lossesB

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0RA(E TEST ON AD.C. SHUNT MOTOR

Experiment no:

0RA(E TEST ON A D.C. SHUNT MOTOR

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AIM : To obtain the 2erformance characteristics cur%es of a D.C. shunt motor b) conducting

brae test on it.

NAME PLATE DETAILS:

S.No Tpe DC S!"nt Motor

', R#tin$% &.'HP

'2 *o+t% 22' * DC

'& C"rrent ,2 A

'9 Ex-. *o+t% 22' * DC

' Ex-. C"rrent '. A

' D"t S ,

'/ In%. C+#%% 0

'= Spee1 ,'' rpm

APPARATUS:


', *o+tmeter 5'6&''7* M.C ,

'2 Ammeter 5'62'7A M.C 2

'& Ammeter 5'6,'7A M.C ,

'9 R!eo%t#t &' o!m8,.2A 6 ,

' T#-!ometer 6 Di$it#+ ,

' F"%e 2'A 6 2

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THEOR:

$t is a simple method of testing low rating DC machines and consists of appl)ing a brae

to a water/cooled drum mounted on the motor shaft. The four important characteristics cur%es of a D.C. Shunt Motor, namel), Tor-ue, Speed,

$nput power" # 0.

Speed ;egulation * P !'o oad speed " / ! ull load speed "Q > ull oad. Speed *

The size of the motor that can be tested b) this method is limited from the consideration

of the heat that can be dissipated at the brae drum

Ahere the output power e#ceeds about 1 .2., or where the test is of long duration, it s

necessar) to use a water cooled brae drum.

PROCEDURE:

0. Connect the circuit as per the Circuit diagram.

1. $nitiall) the starter must be in off position.


5. Start the D.C. motor using the three point starter and thereb) ad6ust the speed to its rated speed

using field rheostat.

7. 'ote down the readings of 4oltmeter &


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O. Ahen the full load is reached, slowl) reduce the load and switch off the Motor from 114

D.C. Suppl) b) opening the D2ST Switch

O0SER*ATION TA0LE:

S.No Inp"t

*o+t#$e 5*7

Arm#t"re

C"rrent

Fie+1

C"rrent

Sprin$ 0#+#n-e% Spee1

5N7

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CALCULATION TA0LE:

Radius of the Brake Drum, R = ______ mts.

S.No Inp"t

*o+t#$e

5*7

Inp"t

C"rrent

Tor3"e

N6m

5T7

O"tp"t

Poer

Inp"t

Poer

PRECAUTIONS:

0. The field rheostat of the motor must be ept in minimum before switching (' the motor.


3.


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0" Ahat is Speed regulationB

1" Ahat are the different t)pes of motorB

3" Ahat are the characteristics of D.C shunt motorB

5" Ahat is the condition for ma#imum efficienc)B

7" Ahat are the different methods to reduce the iron lossesB

8" Ahat are the application of D.C Shunt MotorB

9."Define armature reactionB

O." Difference between interpole and compensating winding.

N. " Define breae horse power !=..2".

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