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SEPERATION OF CORE LOSSES OF 1-PHASE TRANSFORMER
AIM: To separate the core losses of a given single phase transformer.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
5.
Voltmeter
Ammeter
Watt meter
Rheostat
Tacho meter
( 0-300)V
(0-5)A
300V/5A L.P.F
570/1.2A290/2.8A18/12A
(0-9999)RPM
THEORY:
Due to rotations of iron core of the armature in the magnitude
flux of the field poles there are some losses taking place continuously in
the core known as iron losses or core losses. The iron losses consists of
1.Hysteresis losses.
2.Eddy current losses.
HYSTERESIS LOSS:
This losses is due to the reversal of magnetization of thearmature core passes under N&S of the rotation pole alternately. The
core under goes one complete cycle of magnetic reversal after passing
under one pair of poles. If P is the number of poles , N is the armature
speed in RPM then frequency of magnitude reversals in
f=PN/120
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The losses depends up on the volume and grade of iron
,maximum value of flux density Bmax and frequency of magnetic
reversals. For normal flux densities,hysteresis losses is given steinmetz
formulae, according to this formulae.
Wh = B1.6
max V watts
V = volume of the core in m3
= steimmetz hysteresis coefficient.
These losses can be minimized by detected proper magnetic materials
which has low hysteresis losses.
EDDY CURRRENT LOSS(We):
When the armature core rotates it also cuts the magnetic flux ,
hence an emf is induced in the body of the core according to the law of
electro magnetic induction this emf through small sets up large current
in the body of the core due its small resistance this current is known as
eddy current .
We = K B2
max f2
t2
v2
watt
Where
Bmax =Maximum flux density.
f =Frequency.
t = Thickness of material.
v = Volume of armature core.
It is seen from above that this loss varies directly as the squire of the
thickness of laminations, Hence it should be kept as small as possible.
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PROCEDURE:
1. Connections are made as per the circuit diagram.2. Keep the motor armature rheostat in maximum position and
motor field rheostat in minimum position.
3. Switch on dc supply to the motor.4. Start the motor with the help of 3-point starter.5. Adjust the speed of the motor to rated value with the help of
motor field &armature rheostat.
6. Now switch on the supply to the excitation of alternator circuitand adjust the alternator field rheostat to rated voltage which is
suitable to Lv side of transformer.
7. Calculate the speed of different frequencies are55HZ,52HZ,47HZ,45HZ etc.
8. Note down the readings of the voltmeter,ammeter,wattmeterandmeasure the speed.
9. Now vary the motor armature rheostat until the motor speed toreduce to required value .
10.Again calculate the speed at different frequencies.11.Note down the readings of voltmeter, ammeter, and wattmeter for
different frequencies.
12.Keep the rheostat to initial position and switch off the supply ofthe excitation of the motor.
CALCULATIONS:
Wi = Af+Bf2
Wi /f = A+Bf
Wi = Core losses or iron losses.
Af = Hysteresis losses.
Bf2= Eddy current losses.
N = 120f / p, poles = 4
Hysteresis losses Wh = Af
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Eddy current losses We = Bf2
Core losses = Wh + We
TABULAR FORM:
s.no Iamps Vvolts Nrpm Fhz Wwatts W/FWatt/hz V/fVolt/hz Wh We
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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NO LOAD &BLOCKED ROTOR TEST ON 3- SLIP RING
INDUCTION MOTOR
AIM:
To conduct no load and blocked rotor test on 3- slip ring
induction motor and find efficiency ,slip for a 3- slip ring
induction motor.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
5.
Voltmeter
Ammeter
Watt meter
Tacho meter
3- variable
( 0-600)V
(0-10)A
600V/10A
150V/20A
(0-9999)RPM
415/0-470V
THEORY:
The performance characteristics of an induction motor are
derivable from a circular locus. The data necessary to draw the circle
diagram may be found from no-load and blocked rotor test.
NO-LOAD TEST :
The practice , not possible to run the induction motor
synchronous speed. Instead the motor is run with out any external
mechanical load on it. The speed of rotor would not be synchronous but
very much near to it . So that for all practical purpose. The speed may
be assumed synchronous speed.
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The no-load test is carried out rated voltage. The input power
is measured by two wattmeters. Current Io by ammeter and voltage byvolt meter. As the motor is running light load. The power factor would
be low i.e less than 0.5. Hence total power input will be different of two
wattmeter readings W1&W2. The total power will be Wo.
No-load Wo to the rotor consists of ,
1. Small stator cu loss + small rotor loss.
2.Stator core loss.
3. Core due to friction and windage.
Wo = 3VLIocoso
coso = Wo / 3VLIo
BLOCKED ROTOR TEST:
It is a short circuit test. In this rotor is blocked mechanically and
then we applied armature voltage till the ammeter shows the rated
current.
If the normal voltage is applied to the stator, then
ISN = Is X V/VsPower factor on short circuit is found from
Ws= 3Vs Is coss
coss = Ws /3Vs Is
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PROCEDURE:
NO LOAD TEST:
1. Make the connections as per the circuit diagram.2. for the no load test load is not applied on the rotor pulley.3. By varying the 3 Auto transformer, apply the rated voltage.4. Note down the readings of no load voltage, no load current and
wattmeter readings.
BLOCKED ROTOR TEST:
1. Connect the circuit as per the circuit diagram.2. Connect the load at the output terminals.3. Vary the 3 Auto transformer until the ammeter reads the rated
current.
4. Note the readings of voltmeter, Ammeter and wattmeter.
MODEL CALCULATION:
NO LOAD TEST:
WO = W1 +W 2
coso = Wo / 3VLIo
BLOCKED ROTOR TEST:
Wsc = Ws /3Vs Is
Short circuit input current ISN = ISC x VO/VSC
Short circuit input power WSN = 3 VO ISNcossc
Output power = Full load output power/ power scale
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TABULAR FORM:
NO LOAD TEST:
S.NO IO(Amp) VO(Volts) W1(Watts) W2(Watts) W1+ W2
BLOCKED ROTOR TEST:
S.NO Isc(Amp) Vsc(Volts) W1(Watts) W2(Watts) W1+ W2
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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BREAK TEST ON 3- INDUCTION MOTOR
AIM:
To plot the various performance characteristic curves of a
3- induction motor by conducting the break test on it.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
Voltmeter
Ammeter
Watt meter
Tacho meter
( 0-600)V
(0-10)A
600V/10A
UPF
(0-9999)RPM
THEORY:
It is a direct test on a induction motor . In this load
applying a brake to the pulley mounted on the motor shaft. The brake
band is fixed ith the help of the belt with spring balance . One end of the
belt is fixed spring balance S1 &other is connected to spring balance S2.The motor is run & the load on the motor is adjusted till it carries its
full load current .
Let S1 ,S2 are readings of balances . The net pull on band due to
friction at the pulley is (S1 -S2) lag Wt or 9.81(W1 -W2)
If r = Radius of the pulley in meters.
N = motor of pulley speed in rpm.Shaft torque Tsh = 9.81 (S1 -S2) r N-M
Output power = Tsh 2N/60 = 2NT/60 Watts.
Input power = VI Watts.
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Slip: The difference between synchronous speed Ns 7 actual speed N of
the motor expressd as a 5 of N is called slip.
% Slip = Ns -N/ Ns x100
Torque: It is proposal to product of armature current and flux.
Ta Ia
PROCEDURE:
1. Make the connections as per the circuit diagram.2. Make sure that motor is at the no-load .3. 3- supply is given to stator by closing TPST switch and start the
motor with the help of star-delta starter.
4. Gradually applying the load on motor pulley step wise increases.5. Take the readings of ammeter, voltmeter,wattmeter, spring
balance and speed of motor for each load.
6. Increase the load up to full load current of the motor and take ofammeter, voltmeter,wattmeter, spring balance and speed of motor
for each load.
7. Supply is switched off after removing the load on motor pulley.8. Calculate torque and efficiency and after calculations graph is
plotted between speed,torque,current,slip,power factor, efficiency
to output.
MODEL CALCULATION:
Torque = 9.81(S1-S2) r n-m
Power factor cos = cos[tan-1 3(W1-W2)/ (W1+W2)]
Efficiency = output/ input x100
Output power = 2NT/60
Input power = W1+W2
%Slip = NS-N/NS
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TABULAR FORM:
S.NO
V
volts
I
amp
N
rpm
Spring
balance W1 W2 Input
(W )
T
nm Output
(W)
P.f
cos%Slip
S1
kg
S2
kg
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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SCOTT CONNECTIONS BY USING TWO 1- TRANSFORMER
AIM:
To study Scott connection and compare currents in the primary
and secondary by drawing vector diagram in balance load and un
balanced.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
Voltmeter
Ammeter
Load
3- auto transformer
(0-300)V
( 0-600)V
(0-5)A
(0-10)A
3KW
415V/0-470V
THEORY:
This is a connection in which conversion of power 3- to 2- is accomplished with the help of two transformers since it was first
proposed by Charles scott. It is frequently referred to as scott
connection.
One of the transformer has center tap both on primary winding
is known as the main transformer. Other transformer 86.65 tap and isknown as teaser transformer . One end of teaser primary is joined to the
center tap on primary.
Let the teaser transformer secondary supply a current I2T at unity
power factor . If we neglect magnetizing current Io then teaser primary
current.
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I1T = I2T x Transformation ratio
= I2T x N2/3 N1 /2= 2/3 x I2T= 1.15 x I2T
Where K= N2/ N
1= Transformation ratio of main transformer.
The total current I1M in each half of the primary main transformer
consists of two parts . These are given bellow.
1. One part is that which is necessary to balance the main secondarycurrent I2M . Its value is,
I2M = I2M x N2/ N1
PROCEDURE:
1. Connections are made as per the circuit diagram .2. Switch on the 3- power supply by closing TPST switch .3. Auto transformer output voltage is adjusted to supply rated
voltage of 415v to the primary of main and teaser transformer.
4. For the balanced loads apply equal resistance loads across mainand teaser transformer secondary.
5. Record ammeter and voltmeter readings of primary andsecondary.
6. Repeat the process in step wise up to rated load current oftransformer.7. For un balance loads apply .8. record ammeter and voltmeter readings of primary and
secondary.
9. Repeat above step by applying un equal loads at different points.10.Calculate primary current (I1) by consisting of secondary current
(I2) at different loads and compare with readings obtain by phase
diagram and calculations.
MODEL CALCULATION:
K = V2/V1
I2T= P/COS V
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BALANCED LOADS:
Line current IA = I B = I1T2
+ ( IM)2
K of teaser transformer , K = 1.15 = K
IR = I1T = 1.15 K I2T
IB = IY = I1M= ( K I2M )2+(1/2 I1T)
2
UNBALANCED LOADS:
Line current IA = I B = I1T2
+ ( IM)2
K of teaser transformer , K = 1.15 = K
IR = I1T = 1.15 K I2T
IB = IY = I1M= ( K I2M )2+(1/2 I1T)
2
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TABULAR FORM:
BALANCED LOADS:
S.NO VL(V) IR(A) IY(A) IB(A) I2T(A) I2M(A) V2T(V) V2M(V)
UNBALANCED LOADS:
S.NO VL(V) IR(A) IY(A) IB(A) I2T(A) I2M(A) V2T(V) V2M(V)
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
RESULT:
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REGULATION OF 3- ALTERNATOR BY SYNCHRONOUS
IMPEDENCE & MMF METHOD
AIM:
To find the regulation of 3- alternator by synchronousimpedance &MMF method.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
Voltmeter
Ammeter
Rheostat
Tacho meter
( 0-600)V
(0-10)A
(0-5)A
360 /1.2A290/2.8A18/12A
(0-9999)RPM
THEORY:
Regulation :
It is clear that with change in load there is a change in
terminal voltage of an alternator . The voltage regulation of an
alternator is defined as the change in voltage when full load is removeddivided by rated terminal voltage .
% Regulation = EoV/VSynchronous impedance method:
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It is also known as emf method .In this method
following procedure steps are.
1. Occ is plotted from given data .2. Similarly Sc is drawn from the short circuit data .It is a straight linepassing through the origin.
E1 = Zs I1
Zs = E1 (open circuit)/ I1 (short circuit)
3. Calculate Xs = Zs 2- Ra24. Eo = (V Cos + IRa )2+ (V Sin +I Xs)25. % Regulation = EoV/V x100
Mmf method:
It is also known as ampere turns method ,In this
method also utilize the oc & sc data. In this method following
procedure steps are involved ,
1.Occ is plotted from given data .2.Similarly Sc is drawn from data. It is a straight line passing
through the origin both these curves are drawn on common base
of field current .
3.Find IFT = If 12 + If 22 2 If 1 If 2 Cos(180-(90+)Take the corresponding readings voltages for IFT
4.% Regulation = EoV/V x100
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PROCEDURE:
OPEN CIRCUIT TEST:
1. Connections are made as per the circuit diagram.2. A dc shunt motor is used as an prime mover to the alternator .3. Start the dc shunt motor (prim mover) by closing DPST switch &
3-point starter.
4. A 220V dc supply is given to field winding as shown in circuitdiagram.
5. By increasing the field rheostat of alternator , note up to ratedline voltage &field current .
6. Draw the open circuit characteristics graph between field current(If) and phase voltage (Eph).
SHORT CIRCUIT TEST:
1. Connections are made as per the circuit diagram.
2. In this method stator winding is short circuited through ammeter.
3. By adjust the rated field current to zero by drawing the field rheostat.
4. By increasing the field rheostat & note down Ifand short circuit
current (ISC).
5. Note down the readings of ISC
& If
up to rated current .
6. Armature resistance is find out by using multimeter.
7. Effective resistance Rac =1.6 xRdc.
8. Draw the graph between ISC & If .
MODEL CALCULATION:
EMF METHOD:
Impedance Zs = V1/I1
Reactance Xs = ZS2
- RAC2
EO = (V cos + IR)2 + (Vsin + I XS)
2
% Regulation = Eo - V/V
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MMF METHOD:
EPH = V + I a Ra cos
If= If12+ If2
2+ 2 If1 If2 cos (180-(90+ ))
TABULAR FORM:
OC TEST:
S.NO If(Amps) EPH(Volts)
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SC TEST:
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motorfield rheostat in minimum position.
RESULT:
S.NO If(Amps) EPH(Volts)
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OC &SC TEST ON 1- TRANSFORMER
AIM:
To find the regulation and efficiency of a given 1-transformer by conducting oc & sc tests.
APPARATIS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
Voltmeter
Ammeter
wattmeter
( 0-150)V
(0-20)A(0-2)A
150V/5A LPF
150V/20A UPF
THEORY:
The performance of a 1- transformer can be calculated onthe basis of its equivalent circuits. Which contain four main parameters.
The equivalent resistance R01 as referred to primary (or secondary R02)
. The equivalent leakage reactance Xo as referred to primary (or
secondary).These parameters can be easily determined by two tests .
1.Open circuit test.2.Short circuit test.
Open circuit test:
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1. The purpose of this test is to determine no load loss or core loss& no load Io which is helpful in finding Xo Ro.
2. One winding of the transformer which over is convenient butusually high voltage winding is left open and other is connected
to its supply of normal voltage & frequency.3. Wattmeter , voltmeter & ammeter are connected in the low
voltage winding in the present case.
4. With normal voltage applied to the primary normal flux will beset up in the core . Hence normal iron loss will occur . Which are
recorded by the wattmeter.
5. If W is the wattmeter reading then,W =V1 IO CosOCosO = W / V1 IO
I = IO Sin O
Iw = IO COS O
Xo = V1/ I
Ro = V1/ Iw
Short circuit test:
1. This is an economical method for determining the following.2. Equivalent impedance (Z1 or Z02) , leakage reactance (X01 or X02) &
Total resistance (R01 or R02) of the transformer as referred to the
winding in which the measuring instruments are placed.
3.
Copper loss at full load . This loss is used in calculating the efficiencyof a transformer.
4. In this test the one winding is usually the low voltage winding issolidly short circuited by a thick conductor.
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5. Since in this test the applied voltage is a small percentage of thenormal voltage , the mutual flux is also a small percentage of its
normal value.
6. Hence core losses are small with the result that the wattmeterreading represent .The full load copper loss or I2 R loss for the wholetransformer i.e both primary and secondary copper loss.
7. If Vsc is the voltage required to calculate rated load currents thenZ01 = VSC/I1
W = I12R01
R01 = W/ I12
X01= Z012R01
2
PROCEDURE:
OC TEST:
1. Connections are made as per the circuit diagram.2. First make the auto transformer output voltage zero & HV open.3. Give the supply by closing DPST switch &adjust output voltage of
the autotransformer equal to rated LV winding.
4. Note down readings of wattmeter , no-load voltage (Vo) & no-loadcurrent (Io).
SC TEST:
1. Connections are made as per the circuit diagram.2. First make the auto transformer output voltage is zero.3. Adjust the auto transformer output voltage such that rated
current flows in HV side.
4. Take the readings of power , short circuit current & short circuitvoltage.
5.
Calculate the parameters of equivalent circuit , efficiency & %regulation on 1- transformer for given load &power factor.
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MODEL CALCULATIONS:
OC TEST:
Coso
= WO/V
OI
O
Sino = 1- Cos2 o
RO = VO/ IO Coso
XO = VO/ IO Sino
K = V2/V1
SC TEST:
Z02 = VSC /I SC
R02 = WSC / ISC2
X02 = Z022
- R 022
R01 = R02 /K2
X01 = X02 /K2
Efficiency = X KVA Cos/ X KVA Cos + Wi + X2
Wcu X 100
% Regulation = I2 (R02 Cos + X02 Sin)/ V2 X 100
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TABULAR FORM:
OC TEST:
S.NO VO (Volts) IO (Amps) WO (Watts)
SC TEST:
S.NO VO (Volts) IO (Amps) WO (Watts)
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PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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SUMPNERS TEST ON PAIR OF 1- TRANSFORMERS
AIM:
To determine the efficiency & regulation of a 1- transformerat different loads by conducting sumpners test.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
Voltmeter
Ammeter
wattmeter
3- auto transformer
(0-600)V
( 0-150)V
(0-5)A(0-20)A
150V/5A
150V/20A
415V/0-470V
THEORY:This test is also known as back to back test. It provides
data for finding regulation & efficiency under load condi tons and is
employed only when two similar transformers are available . One
transformer is loaded all the other hand both are connected to supply
.The power taken from the supply the supply is that necessary for
supplying the losses of both transformer and are negligible loss in the
control circuit.
When the primary of two transformers are connectedin parallel across the same supply switch S open the wattmeter W1reads core loss of the both transformer .
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Secondarys are so connected that their potentials are inopposite direction to each other. Hence W1 reads the core loss and W2
reads full load copper loss .Applying rated voltage all primary side with
the help of auto transformer . The voltmeter reading s across the switch
it will read zero . But it reads other value than switch OFF the power
supply & reverse the terminals of the transformer.
PROCEDURE:
1. Connections are made as per the circuit diagram.2. Apply rated voltage on primary side with help of auto
transformer.
3. observe that the readings of voltmeter across the switch S iszero or not. If it reads other value than switch OFF the powersupply and reverse the any one of secondary of transformer
terminals.
4. Now close the switch by increase 1- variac from zero positionup to attaining rated secondary current from the secondary
circuit.
5. The readings of two watt meters will directly give the iron &copper loss of both transformer.
6. Note down the voltmeter & ammeter readings of both primarysecondary.
7. Core loss & copper loss of each transformer is calculate bydividing by 2.
8. Calculate regulation of each transformer.MODEL CALCULATIONS:
Coso = WO/VO IO
IW=IO Coso
I= IO Sino
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RO = VO/ IW
XO = VO/I
R02
= RSC
= WSC
/ ISC
2
ZSC = VSC /I SC
X02 = XSC= ZSC2
- RSC2
Efficiency = X KVA Cos/ X KVA Cos + Wi + X2
Wcu X 100
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TABULAR FORM:
S.NO
VO(Volts) I
O(Amps) W
O(Watts) V
SC(Volts) I
sc(Amps) W
sc(Watts)
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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DETERMINATION OF Xd & Xq BY SLIP TEST
AIM:
To determine the values of Xd & Xq by conducting slip test
on 3- salient pole transformer.
APPARATUS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
Voltmeter
Ammeter
Rheostat
Tacho meter
( 0-150)V
(0-5)A
18/12A570/1.2A
(0-9999)RPM
THEORY:
In this test the value of Xd & Xq can be determined by
synchronous machine given by a separate prime movers at a speed
slightly less that synchronous speed. The field winding is left open &
balance voltages of reduced magnitude around 25% of rated value &
rated frequency i.e applied across the armature terminals under this
condition the relative velocity between field poles & rotating armature
.Flux is equal to the difference between the synchronous speed and rotorspeed NsN i.e slip speed .
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At one instant when the peak of armature flux wave is in
line with field poles or direct axiss the reluctance offered by the smallair gap is minimum .At this instant the applied terminals voltage per
phase divided by corresponding armature current per phase gives at
this reactance.
Xd = Vmax/IminAfter one quarter of slip cycle the peak value of the
alternator flux adder all the entire poles or q-axiss of the field poles.The reluctance offered by long reluctance is maximum . At this instant
the ratio of armature terminals voltage per phase to corresponding
armature current per phase to given axis.
PROCEDURE:
1. Connections are made as per the circuit diagram.2. By using the DPST switch give the supply to the motor.3. By varying armature or field rheostat adjust the prime mover speed
less than the synchronous speed.(i.e slip
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S.NO Vmin(Volts) Vmax(Volts) Imin (Amps) Imax (Amps)
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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NO LOAD & BLOCKED ROTOR TEST ON 1- INDUCTION
MOTOR
AIM:
To find the parameters & equivalent circuit of a 1- inductionmotor by conducting no load blocked rotor test on it.
APPARATIS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
Voltmeter
Ammeter
wattmeter
( 0-300)V(0-150 ) V
(0-15)A
(0-10)A
300V/10A LPF
150V/20A UPF
THEORY:
No load test:
Purpose of this test is to deter mine no load loss or core
loss at no load current Io which is helpful for finding Xo & Ro.One winding of the transformer which ever is convenient but
usually high voltage winding is left open and the other is connected to its
supply at normal voltage & frequency . A wattmeter W and voltmeter V& all ammeter are connected .
WO = VO IO COS OCOS O = WO/ VO IO
Magnetizing component I = IO Sin OXo = VO/ I
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Working component Iw = IO COS ORo = VO/ Iw
Blocked rotor test:
It is also known as short circuit test . This test is used to find
1. Short circuit current with normal voltage applied to stator .2. Power factor on short circuit. Both values are used in
construction of circle diagram.
3. Total leakage reactance X01 of the motor as referred to primary .4. Total resistance of the motor R01 as reforod to primary.
PROCEDURE:
NO LOAD TEST:
1. Connections are made as per the circuit diagram.2. Before giving supply , remove the load on the motor.3. Give the 1- supply to the motor circuit and by varying the auto
transformer give the rated voltage in the voltmeter.
4. Note down the no load current & power in ammeter &wattmeter.
BLOCKED ROTOR TEST:
1. Connections are made as per the circuit diagram.2. Before giving supply tightly fix the rotor with the help of belt.3. Give the supply to circuit & varying the ammeter & up to
attaining rated current in the circuit.
4. Note down the readings of voltmeter , ammeter & wattmeter.
MODEL CALCULATIONS:
NO LOAD TEST:
Coso = WO/VO IO
IW=IO Coso
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I= IO Sino
RO = VO/ IW
XO
= VO/I
BLOCKED ROTOR TEST:
R02 = RSC = WSC/ ISC2
ZSC = VSC /I SC
X02 = XSC= ZSC2
- RSC2
R2'
= R01 - R 1
X1 = X 2'= XSC/2
Slip, S = NsNr /Ns
XO/2 =
R2' /2(2-S) =
X 2' /2 =
TABULAR FORM:
NO LOAD TEST:
S.NO VO(Volts)IO(Amps) WO(Watts)
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BLOCKED ROTOR TEST:
S.NO
VSC
(Volts) Isc
(Amps) Wsc
(Watts)
PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
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V AND INVERTED V CURVES
AIM:
To draw the V and inverted V curves of a given
synchronous motor.
APPARATIS:
S.NO APPARATUS RANGE TYPE QUANTITY
1.
2.
3.
4.
5.
Voltmeter
Ammeter
Wattmeter
Lamps
Load
( 0-600)V
(0-5)A
(0-10)A
(0-20)A
600V/10A UPF
600V/10A LPF
230V/60watts
250V/3kw
THEORY:
When the power input to the motor is constant the armature
current increases . When the excitation is either decrease or increase
from the normal value . The graphically relation between the armaturecurrent Ia and the excitation current If curves resembles the shape of V
& therefore known as the V-curves of synchronous motor . It is from
that the current drawn by the motor is minimum at unity power factor
is either leading or lagging . Under lagging power factor the
synchronous motor takes lesses field current for a given armature
current as compare to the field current under leading power factor.
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The relationship between power factor &field current . The
curve resembles & shape as inverted V curve . It is known as inverted V
curves of synchronous motor.
PROCEDURE:
1. Connections are made as per the circuit diagram.2. A rated Dc supply is given to the Dc shunt motor is started with
the help of 3-point starter.
3. Adjust the speed of the motor to a rated value by adjusting itsfield rheostat.
4. Exciting field winding of synchronous motor by the Dc supply tothis circuit by closing the DPST switch2.
5. Observe the reading of voltmeter that is the voltage of bus barsbetween the lines.
6. The synchronous motor voltage is meet by voltmeter.7. Adjust the excitation of synchronous motor such that the
voltmeter V1 connected across armature terminals should be
equal to the bus bar voltage.
8. The synchronous motor is acting as a synchronous generator untill its operation ,when synchronization occur that is all the 6-
lamps bright at one time & dark at another time.
9. Adjust the speed of the Dc motor slightly such that the darkperiod of lamp should be more at this condition DPST switch
closed.
10.Now , the supplied Dc motor is taken OFF.11.By this synchronous generator will convert to synchronous motor
& synchronous Dc motor is converted into Dc generators.
12.By changing the excitation (If) the readings of ammeter &wattmeter readings are taken.
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MODEL GRAPHS:
TABULAR FORM:
S.NO If(Amps) W1(Watts) W2(Watts) IA(Amps) Coso
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PRECAUTIONS:
1.Avoide loose connections.
2.Take the readings with out parallax error.
3.Double check the circuit before giving the supply.
4.The motor armature rheostat in maximum position and motor
field rheostat in minimum position.
RESULT:
Recommended