1.OPEN CIRCUIT AND SHORT CIRCUIT TEST OF TRANSFORMER
AIM:To conduct open circuit and short circuit test in given transformer. Predetermine the
following
1. Efficiencies at various loads and power factors
2. Regulation at various power factor and loads
MACHINE DETAILS:-
METERIALS REQUIRED:1.
2.
3.
4.
5.
6.
Ammeter (0-2.5A) MI
1NO
Ammeter (0-15A)MI
1NO
Volt meter (0-250v)
1no
Voltmeter (0-50v) MI
1NO
Wattmeter (150V,5A,LPF) 1NO
Wattmeter (150V,15A,UPF) 1NO
THEORY:The purpose of the OC test to determine the no load loss (core loss) at rated voltage and
frequency. Shunt branch parameters of equalent circuit r0&x0 and the no load current of the
transformer on winding of the transformer. In the open circuit test the primary load current is very
small(2.6% of rated current )copper loss is negligibly small in the primary and is nil in the
secondary is opened. The equalent circuit parameters r0&xo referred to LV side can be calculated
from the test result.
The no load power loss, Pi=V0*I0*COS φ0
COSφ0=Pi/V0*I0
Magnetising component of I0 =Im=I0SIN φ0
Energy component of I0=Ie=I0COS φ0
The noload resistance R0=V0/Ie and the no load reactance X0= V0/Im
These values can be transferred to hv side as
R0’=R0(V2/V1)2 and X0’=X0(V2/V1)2
SC Test is to conduct for determining the full load copper loss and the equalent resistance and
resistance of the transformer as refferd to the metering side. In this test one winding usually LV
side is solidly short circuited and a low voltage (2-12% of primary voltage ) is applied to the HV
side such that rated current flows through the winding since applied voltage is very low ,iron
losses are very small and may be neglected. Hence the wattmeter shows the full load copper loss
Pcu for the bwhole transformer. If VSC is the voltage required to circulate the rated current I2(KVA X
1000/V1) Then the equavalent circuit parameters can be found as Z02=VSC/I2 and R02=PCu
Then X02= 𝒁𝟎𝟐𝟐 + 𝑹𝟎𝟐 These parameters can be transferred to the LV side as
R2’=R2(V2/V1)2 and X2’=X2(V2/V1)2 secondary side R02 and X02 the regulation at any PF and loading
factor(x) can be predetermind as regulation= XI2(R02 COS φ0+- X02 SIN φ0)/V2 Where (+) for lagging
and(-) for leading power factors) from the full load copper loss and iron loss the efficiency at any
loading factor and pf can be pre determind as
𝑿𝟏𝟎𝟎𝟎𝑲𝑽𝑨𝑿.𝑷𝑭
Efficiency= 𝑿𝟏𝟎𝟎𝟎𝑲𝑽𝑨𝑿𝑷𝑭+𝑿𝟐𝑷𝒄𝒖+𝑷𝒊
PROCEDURE:OC TEST
1. Collect the materials for the given work.
2. Connection are done as shown in connection diagram.
3. Keep auto transformer at zero position.
4. Adjust the auto transformer up to rated voltage.
5. Take voltmeter, ammeter and wattmeter reading.
PROCEDURE:SC TEST
1. Collect the materials for the given work.
2. Connection are done as shown in connection diagram.
3. Keep auto transformer at zero position.
4. Adjust the auto transformer up to rated current
5.Take voltmeter, ammeter and wattmeter reading.
𝑽𝑶𝑪
𝑰𝑶𝑪
𝑾𝑶𝑪
𝑽𝑺𝑪
𝑰𝑺𝑪
𝑾𝑺𝑪
MODEL CALCULATION
OC TEST
𝑽𝑶𝑪 =
𝑰𝑶𝑪 =
𝑾𝑶𝑪 =
𝑾𝑶𝑪==𝑽𝑶𝑪 𝑰𝑶𝑪 𝑪𝑶𝑺∅𝟎
∅𝟎 =𝒄𝒐𝒔−𝟏 (𝑽
𝑾𝑶𝑪
𝑶𝑪 𝑰𝑶𝑪
)
Wattles component
𝒊𝒘 = 𝒊𝟎 𝒄𝒐𝒔∅𝟎
Magnetizing component
𝒊µ = 𝒊𝟎 𝒔𝒊𝒏∅𝟎
𝑽
𝑹𝟎 = 𝑰𝑶𝑪
𝑾
𝑽
𝑿𝟎 = 𝑰𝑶𝑪
µ
These values can be transferred to hv side
R0’=R0 x K2
SC TEST
X0’=X0 x K2
𝑽𝑺𝑪 =
𝑰𝑺𝑪 =
𝑾𝑺𝑪 =
Zsc=Vsc/Isc
𝑹𝒔𝒄 = 𝑽𝒔𝒄/𝑰𝒔𝒄𝟐
Xsc= (𝒁𝒔𝒄² − 𝑹𝒔𝒄²)
Z02=Vsc/ISC
R02=PCU/ISC2
X02= 𝒁𝟎𝟐𝟐 + 𝑹𝟎𝟐
These values can be transferred in to LV
R01=R02/K2
X01=X02/K2
TO DRAW EFFICIENCY CURVE FOR A GIVEN P.F
Out put at X times F.L=X(rated KVA x 1000) cos∅
Core loss Wi= W0
Copper loss Wcs= X²Wsc
Efficiency=(Output /output+losses) x100.
KVA Curresponding to maximum efficiency=KVArated X
𝑪𝒐𝒓𝒆 𝒍𝒐𝒔𝒔
𝑪𝒐𝒑𝒑𝒆𝒓 𝒍𝒐𝒔𝒔
then find efficiency as usual.
Sl no
Load
Output(Watt) Wi(watt)
Wcx(watt)
Input
%efficiency
TO DRAW REGULATION V/S PF CURVE
% regulation at F.L for a given P.F=
Sl No
cos∅
𝑰𝒓𝒂𝒕𝒆𝒅(𝑹𝟎𝟐𝒄𝒐𝒔∅±𝑿𝟎𝟐𝒔𝒊𝒏∅
𝑽𝟐
sin∅
% Regulation
Procedure:OC Test
1.
2.
3.
4.
5.
Make connection as per the circuit diagram
Keep the autotransformer in minimum position
Adjust the auto transformer upto rated voltage of the transformer
Take the meter readings and tabulate the readings
Finish the work
SC Test
1.
2.
3.
4.
5.
Make connection as per the circuit diagram
Keep the autotransformer in minimum position
Adjust the auto transformer upto rated current of the transformer
Take the meter readings and tabulate the readings
Finish the work
RESULT:-Conducted the OC and SC test on the given single phase transformer and predetrermine
the following
1.
2.
3.
4.
5.
Efficiencies at various loads and power factors
Regulation at various loads and power factors
Equavalent circuit reffered to hv and lv side
Maximum efficiencies at unity PF=
Maximum efficiencies at 0.8PF=
2.LOAD TEST ON SINGLE PHASE TRANSFORMER
AIM:To conduct a no load test on given SINGLE PHASE TRANSFORMER and determine the
regulation for defferent load.
MACHINE DETAILS:-
METERIALS REQUIRED:1.
2.
3.
4.
5.
6.
Ammeter (0-15A) MI
Voltmeter (0-150v) MI
Wattmeter (300v,15A,upf)
Ammeter (0-5A) MI
Voltmeter (0-250v) MI
Wattmeter (300v,30A,upf)
1NO
1NO
1NO
1NO
1NO
1NO
THEORY:In this test the efficiencies and regulation are detrermind by direct loading of the given single
phase transformer . this test is very often carried out in practice excepting for small sizes ,owing to
the difficulty of obtaining a suitable load and the loss of power involved.
When ever a transformer is loaded its secondary terminal voltage changes with increased load ,if
the supplied primary voltage is held constent.the change in secondary voltage from no load to full
load expressed ias percentage of no load voltage is known a voltage is known as voltage regulatin
of a transformer (ie, secondary voltage at noload –secondary voltage at full load)
𝑬𝟐−𝑽𝟐
(the
𝑬𝟐
secondary rated voltage of a transformer is equal to the secondary voltage at no load,ie,E2
The efficienciy of a transformer is defaind as the ratio of output power to input power,thus
efficeiency=output power/input power
In this experiment input power is measured directly from the wattmeter connected in the primary
side and output power is obtained by multiplying the volt meter reading and ammeter reading in
the secondary side.
PROCEDURE:1.
2.
3.
4.
Connect the circuit diagram as per the circuit diagram
Adjust the autotransformer till the voltmeter reads rated voltage.
Note the no load readings and enter them as first set of readings in tabular column.
Load the transformer gradually and take all meter readings each time till the secondary
current reaches rated value.
5. Tabulate the readings. And finish the work
TABULATION
Sl
No
I1 in
Amps
V1 in
volts
W in
watts
I2 in
Amps
V2 in
volts
Input
in
watts
Output=V2xI2 %efficiency %
Regulation
CALCULATION
Output=V2xI2.
Input= W
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
Regulation=
𝒐𝑽𝟐−𝑽𝟐
x100.
𝒐𝑽𝟐
RESULT:Load test on single phase transformer is conducted and efficiency and regulation curve were
plotted.
3.SWIMBERN’S TEST
AIM:Conduct no load test on dc shunt motor and [predetermine the efficiency of the machine under
the following working conditions.
a)machine working as a generator
b) Machine working as a motor
c) plot efficiency vs output
MACHINE DETAILS:-
METERIALS REQUIRED:1)
2)
3)
4)
5)
6)
7)
Ammeter
Ammeter
voltmeter
voltmeter
Rheostat
Rheostat
Tachometer
0-5A MC
0-3A MC
0-300v MC
0-30v MC
100Ω,5A
370Ω,1.1A
2NO
1NO
1NO
1NO
1NO
1NO
1NO
THEORY:This is a no load test to determine the losses of the machine. the losses in the motors are
Iron loss or core losses, frictional losses, windage losses, arm copper losses
Work as generator
Efficiency=
𝒐𝒖𝒕𝒑𝒖𝒕
𝒐𝒖𝒕𝒑𝒖𝒕−𝒍𝒐𝒔𝒔𝒆𝒔
Work as motor
Efficiency =
𝒊𝒏𝒑𝒖𝒕−𝒍𝒐𝒔𝒆𝒔
𝒊𝒏𝒑𝒖𝒕
PROCEDURE:1.
2.
3.
4.
5.
6.
Connection are as shown in connection diagram.
Armature rheostat at maximum position.
Field rheostat at minimum position.
Switch on the supply and run the motor at no load.
Adjust the field rheostat bring motor speed to rated speed.
Note the readings and tabulate the readings
TABULATION
Si
Voltage V
no
(in volts)
𝑰𝑺𝑯
AMPS
𝑰𝑨𝟎
AMPS
𝑰𝟎= 𝑰𝑨𝟎 + 𝑰𝑺𝑯
AS MOTOR:
Sl No
Fraction
of load(X)
Voltage(v)
Current Ia
in Amps
Total loss= Input
X²Ia²Ra+Wc power
o/p
power
efficiency
Voltage(v)
Current Ia
in Amps
Total loss= Input
X²Ia²Ra+Wc power
o/p
power
efficiency
AS GENERATOR
Sl No
Fraction
of load(X)
CALCULATIUON:
Constant losses Wc= V ( Iao+ Ish)-Iao²Ra.
AS MOTOR:
I/p power=F.L o/p Power+Ia²Ra+Wc.,O/p power= V𝑰𝑳 , 𝑰𝑳 =Ia+ Ish.
Total loss= Ia²Ra+Wc.
O/p=I/p-Losses.
𝑶/𝒑
Efficiency= 𝒊/𝒑 x100.
AS GENERATOR:
Full load o/p power=Vx𝑰𝑳 .
I/p=o/p+ losses.
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
RESULT Efficiency of the DC shunt machine when work as
1)Motor
2) Generator are pre-determined also efficiency curves are plotted.
4.LOAD TEST ON A DC SERIES MOTOR
AIM;
To conduct a load test on DC series motor and plot the following graph.
1)
2)
3)
4)
Torque v/s armature current
Speed v/s armature current
Speed v/s torque
Efficiency v/s o/p
MACHINE DETAILS:
APPARATUS REQUIRED:
1) Voltmeter
2) Ammeter
3) Tachometer
0-250V(MC)
0-15A(MC)
1No
1 No
THEORY:
In series motor the torque is directly proportional to armature current. Speed N is
proportional to Ed/∅. In a series motor the field carries same current as the armature ie, ∅
∝Ia. The series motor cannot be started without load.
Toque= (S1-S2)xgr
Output=
𝟐П𝑵𝑻
.
𝟔𝟎
Input=VI.
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
TABULATION:
Sl
N
o
Voltage(V
)
Speed(RPM
)
Spring balance
S
1
S
2
S1~s
2
CALCULATION:
V= ………………..
Speed,N=………………………….
Spring balance, S1=…………………………….
S2=……………………………………………..
Torque,T= (s1~s2)rg,
r=Radius of break drum
g= 9.8
Output=
𝟐П𝑵𝑻
.
𝟔𝟎
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
Torque
=
(S1s2)rg
Output(W
)
Input(W
)
Efficiency(%
)
PROCEDURE:
1)
2)
3)
4)
5)
6)
Connections are made as per diagram.
Apply a small load to the motor and start the motor.
Note the meter readings
Vary the spring balance at different load.
Note the corresponding readings.
Tabulate the reading and plot the graph.
RESULT:
The load test on series motor is conducted and plotted the graphs.
5.LOAD TEST ON A DC SHUNT MOTOR
AIM;
To conduct a load test on DCshunt motor and plot the following graph.
5)
6)
7)
8)
Torque v/s armature current
Speed v/s armature current
Speed v/s torque
Efficiency v/s o/p
MACHINE DETAILS:
APPARATUS REQUIRED:
1)
2)
3)
4)
5)
Voltmeter 0-250V(MC)
Ammeter 0-15A(MC)
Ammeter 0-3A (MC)
Rheostat 500Ω,3A
Tachometer
1No
1 No
1No
1No
THEORY:
A load test is direct method,and this method is used only for small motors, because in the case
of large motors it is difficult to dissipate large amount of heat generation
Toque= (S1-S2)xgr
Output=
𝟐П𝑵𝑻
.
𝟔𝟎
Input=VI.
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
TABULATION:
Sl
N
o
Voltage(V)
Speed
(RPM)
Ish
Ia
IL=I
a+
Ish
CALCULATION:
V= ………………..
Speed,N=………………………….
Spring balance, S1=…………………………….
S2=……………………………………………..
Torque,T= (s1~s2)rg,
r=Radius of break drum
g= 9.8
Output=
𝟐П𝑵𝑻
.
𝟔𝟎
𝑶/𝒑
%efficiency= 𝒊/𝒑 x100.
Spring balance
S1
S2
S1~s2
Torque
=
(S1s2)rg
Outp
ut(W
)
Input(W
)
Efficien
cy(%)
PROCEDURE:
1) Connections are made as per diagram.
2) Rheostat kept in min. position
4) Start the motor using 4 point starter
5)Note the meter readings
6) Vary the spring balance at different load.
7) Note the corresponding readings.
8) Tabulate the reading and plot the graph.
RESULT:
The load test on shunt motor is conducted and plotted the graphs.
6.POLARITY TEST AND TURN`S RATIO TEST ON SINGLE PHASE T RANSFORMER
Aim : To conduct polarity test, and determine turn`s ratio, transformation ratio, and magnetizing
component of No Load current of single phase transformer. (115/ 220 V, 5 KVA)
Apparatus required :
Theory:- Turns ratio of a transformer = No of turns of primary/No of turns of secondary.
Transformation ratio K = Secondary induced EMF/ Primary induced EMF= E2/E1
E1 = 4.444 φm.f.N1Volts., and E2 = 4.444 φm.f.N2Volts
... K= E /E
2
1
K =4.444 φm.f.N2/4.444 φm.f.N1 , =N2/N1
...Turns ratio, N1/N2=E1/E2
No load input power, W0= V0 I0 Cosφ0, Cosφ0= W0/ V0 I0,
Magnetizing component of no load current Iµ = I0 Sinφ0
... φ0 =Cos-1(W0/ V0 I0)
Procedure:- 1) Polarity test.
1 Connections are made as shown in figure (1)
2. Checked the connections and given a specified voltage to primary.
3. Noted the volt meter reading and verified the polarity of the transformer.ie If the
voltmeter reading in the inter connected voltmeter is greater than the input voltage, then
the polarity is additive , So Opposite polarity on the other adjacent terminal on secondary.
4. Interchanged the connections to confirm first determined polarity.
Turn`s ration and transformation ratio;
1. Connections are made as in figure (2)
2. Checked the connections and given the supply gradually from minimum voltage to
rated voltage of primary using autotransformer.
3. Noted the V/m readings on primary and secondary and the A/m and W/m reading
when applying the rated primary voltage.
4. Completed the experiment neatly and correctly.
Result:- Checked the polarity and determined the turns ratio transformation ratio, and
magnetizing component of no load current of 115/220/V 5 KVA transformer.
Turns ratio=
Transformation ratio=
Magnetizing component of no load current
Iµ =
Determined the polarity of the transformer also.
Sl No
Prim V/m
reading E1
Sec V/m
reading E2
Watt meter A/m
reading W0 reading I0
Turns ratio
Transf.
ratio =K