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Ex. No:1 OPEN CIRCUIT AND LOAD CHARACTERISTICS OF
Date : SEPARATELY EXCITIED DC GENERATOR
Aim:
1. To draw open circuit characteristics of the given separately excited DC
generator at rated speed and determine the critical resistance.
2. To determine load characteristics (Internal & External) of the given DC
separately excited generator.
Apparatus required:
Sl.No. Name Range Type Quantity
1 Voltmeter (0-300V) MC 1
2 Ammeter (0-10A)
(0-2A)
MC
MC
1
1
3 Rheostat 300/1.4 A Wire wound 2
4 Tachometer (0-1500) rpm Analog/Digital 1
5 Connecting wires Required
Formula:
Where, Rc Critical resistance
Eg Incremental generated EMF (measured from the linear portion
on the OCC)
If Incremental field current (measured from the linear portion on
the OCC).
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Circuit Diagram:
+
-
DPSTSwitch
Fuse
220VoltsD.C
Supply
+
-
220
VoltsD.CSupply
LF
A
DPSTSwitch
Fuse
F1
F2
A1
A2
3-Point Starter
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
Fuse
Fuse
VariableResistive
Load
(0-10 A) MC
(0-300 V)
MCDPST
Switch
10 A
10 A
A
A
V
(0-2 A)
MC
F1
F2
Fuse
Fuse
300 /
1.4 A
15 A
15 A
M G
15 A
15 A
300 /
1.4 A
Fuse Rating Calculation
125% of Rated Current
Motor =
Generator =O.C & Load Characteristics of DC Separately Excited Generator
Generator Name Plate Details
KVA________
RPM________
Volts________
Amps________
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Precaution:
1. The field rheostat on the motor side must be kept at minimum resistance position at the
time of starting.
2. The field potentiometer on the generator side must be kept at minimum potential
position at the time of starting.
3. DPST switches must be kept open at the time of power on.
Procedure:
1. Connections are given as per the circuit diagram.
2. Observing the precautions the motor side DPST switch is closed.
3. The motor is started with the help of three- point DC starter slowly.
4. The speed is measured with the help of a hand tachometer.
5. If the speed is below the rated value, then it is brought to the rated value by adjustingthe field rheostat.
6. With DPST switch on the generator field side open, the voltmeter reading is noted
down. (This is the residual voltage at the rated speed at which the motor-generator set is
running now.)
7. The DPST switch on the generator field side is closed.
8. By adjusting the potentiometer on the generator field side suitably for various
increasing field currents, note down the terminal voltages till around 125% of the rated
voltage. The speed is maintained constant throughout this process.
9. The generator terminal voltage is minimized to zero.
10.The speed is brought down to minimum value and the motor is switched off with the
help of DPST switch. (Note the starter holding coil releasing the handle else bring it
back to start position)
Tabulation:
Speed = _________rpm
Residual voltage = ________ Volts
S. No. If(amps) Eg (volts)
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Model graph:
Load Characteristics:
Precaution:
1. The field rheostat on the motor side must be kept at minimum resistance position at the
time of starting.2. The field potentiometer on the generator side must be kept at minimum potential
position at the time of starting.
3. DPST switches must be kept open at the time of power on.
4. There should be no load at the time of starting.
Procedure:
1. Connections are given as per the circuit diagram.
2. Observing the precautions the motor side DPST switch is closed.
3. The motor is started with the help of three- point DC starter slowly.
4. The speed is measured with the help of a hand tachometer.
5. If the speed is below the rated value, then it is brought to the rated value by adjusting
the field rheostat.
6. By adjusting the potentiometer on the generator side the generator terminal voltage is
brought to the rated value.
Eg E
g
If
If
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7. Load side DPST switch is closed.
8. The load is applied gradually. For various load currents voltmeter and ammeter
readings are noted down till full current of the generator. (Avoid sustained overload.)
9. The load is brought back to initial no load position.
10.DPST switch on the load side is opened.
11.Generator field circuit potentiometer is brought to minimum potential position.
12. DPST switch on the generator field side is opened.
13. The speed is brought down to minimum value and the motor is switched off with the
help of DPST switch. (Note the starter holding coil releasing the handle else bring it
back to start position)
14. Disconnect and return the apparatus.
Tabular column:
Ra = _________ Ohms
Load
current
IL(amps)
Shunt
Field
current
I sh(amps)
Load
voltage
VL(volts)
Armature current
Ia = IL
Generated voltage
Eg = V + Ia Ra
Model graph:
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Ia = IL + I sh Amps
Eg = V + Ia Ra Volts
Ra Armaure resistance ohms
Eg generated voltage volts
V Terminal voltage volts
I sh Shunt field current Amps
Result:
1. The Open Circuit Characteristics of the given separately excited DC generator was
obtained and the Critical resistance at rated speed is found to be ______ohms.
2. The Load Characteristics (Internal & External) of the given separately excited DC
generator was obtained.
Ia
& IL
Eg Vs Ia
V Vs IL
V
&Eg
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Ex. No: LOAD CHARACTERISTICS OF SELF EXCITIED
Date : DC SHUNTGENERATOR
Aim:
1. To determine load characteristics (Internal & External) of the given DC self excited
generator.
Apparatus required:
Sl. No Name Range Type Quantity
1 Voltmeter (0-300) V MC 1
2 Ammeter (0-10) A MC 1
3 Ammeter (0-2) A MC 1
4 Rheostat300 / 1.4 A
100 / 4 AWire wound Each 1
5 Tachometer Analog / Digital
6 Connecting wires Required
Formulae:
Eg = V + Ia Ra
Ia = IL + I sh
Where,
Ra Armature resistance
Eg Generated voltage
V Terminal Voltage
I sh Shunt field current
IL Load Current
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Circuit Diagram:
+
-220 Volts
D.C
Supply
LF
A
DPSTSwitch
F1
F2
A1
A2
3-Point Starter
M
FuseFuse
A
v
Fuse
VariableResistive
Load
(0-10 A)
MC
(0-300 V)MC
(0-2 A)
MC
f1
f2
100 /4A
DPST
SwitchFuse
300 /
1.4 A
15 A
15 A 10 A
10 A
G
A1
A2
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
Generator Name Plate Details
KVA________
RPM________
Volts________
Amps________
Fuse Rating Calculation
125% of Rated Current
Motor =
Generator =
O.C & Load Characteristics of DC Shunt Generator
A
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Precaution:
The field rheostat on the motor side must be kept at minimum resistance position at
the time of starting.
The field rheostat on the generator side must be kept at maximum resistanceposition at the time of starting.
DPST switches must be kept open at the time of power on.
There should be no load at the time of starting.
Procedure:
Connections are given as per the circuit diagram.
Observing the precautions the motor side DPST switch is closed. The motor is started with the help of three- point DC starter slowly.
The speed is measured with the help of a hand tachometer.
If the speed is below the rated value, then it is brought to the rated value by
adjusting the motor field rheostat.
By adjusting the field rheostat on the generator side the generator terminal voltage is
brought to the rated value.
Load side DPST switch is closed.
The load is applied gradually. For various load currents voltmeter and ammeter
readings are noted down till full current of the generator. (Avoid sustainedoverload.)
The load is brought back to initial no load position.
DPST switch on the load side is opened.
Generator field circuit rheostat is brought to maximum resistance position.
DPST switch on the generator field side is opened.
The speed is brought down to minimum value and the motor is switched off (Note
the starter holding coil releasing the handle else bring it back to start position)
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Tabular column:
Ra = ________ Ohms
S.
No.IL(amps)
I sh(amps)
V(volts)Ia = IL + I sh
(amps) Eg = V + Ia Ra
Model graph:
Result:
Ia
& IL
Eg
Vs Ia
VL
Vs IL
VL&
Eg
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Thus the Load Characteristics (Internal & External) of the given self-excited DC
shunt generator was obtained.
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Ex. No: LOAD TEST ON DC SHUNT MOTOR
Date :
Aim:
To perform load test on the given D.C shunt motor and to obtain the performance
characteristics.
Apparatus Required:
Sl.No Name of the apparatus Range Type Quantity
1. Ammeter (0-2) A
(0-20) A
MC Each 1
2. Voltmeter (0-300) V MC 1
3. Tachometer (0-1500) rpmAnalog/Digita
l1
4. Rheostat 300/1.4 A Wire wound 1
5. Connecting wires Required
Formulae:
IL = Ia + I sh
Input power = V x IL (Watts)
Torque (T) = (S 1 ~ S 2) x 9.81 x R (Nm) S 1, S 2 spring balance readings (Kg)
Output power = 2 N T (Watts) N speed of the motor in rpm
60
Efficiency = Output power x 100
Input power Ia - Armature current (Amps) I sh Shunt field current (Amps)
IL - Load Current (Amps) V Supply voltage (Volts)
R Radius of the brake drum = Circumference / 2 (m).
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Circuit Diagram:
+-
220 VoltsD.C
Supply
DPSTSwitch
A1
A2
Fuse
Fuse
15 A
15 A
M
LF
A
F1
F2
3-Point Starter
300 /
1.4 A
A
A
V
(0-20 A) MC
(0-300 V)
MC
(0-2 A)MC
SpringBalance
BrakeDrum
S1 S2
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
Fuse Rating Calculation
125% of Rated Current
Motor =
Load Test on DC Shunt Motor
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Tabular column:
Sl.No
Input
voltage(Volts)
(V)
Load
Current(Amps)
(IL)
Field
Current(Amps)
(Ish)
Armature
Current(Amps)
(Ia = IL - Ish )
Speed(N)
(rpm)
Spring Balance
Readings Torque(T)
(Nm)
InputPower
(Watts)
OutputPower
(Watts)
Efficienc(%)S1
kg
S2kg
(S1~ S2)
kg
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Model Graph:
ELECTRICAL CHARACTERISTICS MECHANICAL CHARACTERISTICS PERFORMANCE CHARS
Torque (T)(Nm)
23
4
1 Output Vs Speed
2 Output Vs % Efficiency
3 - Output Vs Torque
4 Output Vs Armature Current
Speed (N)
% Efficiency ()
Torque (T)Arm. Current (Ia)
Output power in wattsTorque (Nm)Arm. Current (Ia) in Amps
Speed (N)(rpm)
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Precautions:
1. The motor field rheostat must be kept at minimum resistance position at
the time of starting.
2. There should be no load at the time of starting.
Procedure:
Make the connections as per the circuit diagram
Switch on the supply and move the starter handle slowly and gradually to start the motor
Now observe the speed. If the speed is less than the rated speed adjust the field
rheostat and bring the speed to rated value. Readings are taken for no load.
Load on the motor is varied with the help of pony brake arrangement.
Spring balance, ammeter, voltmeter and speed-readings are noted down for various
line currents as the load is increased (till the rated current is reached).
Pour water in the brake drum to avoid over heating.
Unload the machine and bring back the rheostat to minimum position.
Switch off the supply
Result:
Thus the load test on the given DC Shunt motor was conducted and its performance
characteristics were drawn.
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Ex. No: LOAD TEST ON DC SERIES MOTOR
Date :
Aim:
To perform load test on the given D.C shunt motor and to obtain the performance
characteristics.
Apparatus Required:
Sl.No Name of the apparatus Range Type Quantity
1. Ammeter (0-20) A MC 12. Volt meter (0-300) V MC 1
3. Tachometer (0-1500) rpmAnalog/Digita
l1
4. Connecting wires Required
Formulae:
IL = Ia = ISe
Input power = V x IL (Watts)
Torque (T) = ( S 1 ~ S 2 ) x 9.81 x R (Nm) S 1 , S 2 spring balance readings(Kg)
Output power = 2 N T (Watts) N speed of the motor in rpm
60
Efficiency = Output power x 100
Input power
Ia - Armature current (Amps) I se Series field current (Amps)
IL - Load Current (Amps) V Supply voltage (Volts)
R Radius of the brake drum = Circumference / 2 (m)
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Circuit Diagram:
+
-220 Volts
D.CSupply
DPSTSwitch
A1
A2
Fuse
Fuse
15 A
15 A
M
2-Point Starter
A
V
(0-20 A) MC
(0-300 V)
MC
SpringBalance
Brake
Drum
S1 S2
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
Fuse Rating Calculation
125% of Rated Current
Motor =
L A
S1 S2
Load Test On DC Series Motor
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Tabular column:
Sl.
No
Inputvoltage
(Volts)
(V)
Load
Current
(Amps)
(IL = Ia)
speed
(N)
(rpm)
Spring Balance
Readings Torque
(T)
(Nm)
Input
Power
(Watts)
Output
Power
(Watts)
Efficiency
(%)S1kg
S2kg
(S1~ S2)kg
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Model Graph:
ELECTRICAL CHARACTERISTICS MECHANICAL CHARACTERISTICS PERFORMANCE CHARS
% EfficiencySpeed Speed
(N) Torque
Torque (T) rpm Arm. Current(Nm)
Arm. Current (Ia) in Amps Torque (Nm)
Output power in watts
4
1 Output Vs Armature Current
2 Output Vs Torque
3 Output Vs % Efficiency
4 Output Vs Speed
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Precautions:
1. The motor should be started with some load.
2. Brake drum should be cooled throughout the experiment.
Procedure:
1. Connections are given as per the circuit diagram
2. Observing the precautions the DPST switch is closed.
3. The motor is started with the help of two-point dc starter slowly.
4. Load on the motor is varied with the help of pony brake arrangement.
5. Spring balance, ammeter, voltmeter and speed readings are noted down for
various line currents as the load is applied. Care must be taken to avoid the speed
reaching dangerously high values while reducing the load.
6. Pour water in the brake drum to avoid overheating.
7. At a minimum safe load the DPST switch is opened.
8. Disconnect and return the apparatus.
Result:
Thus the load test on the given DC Series motor was conducted and its performance
characteristics were drawn.
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Ex. No: SPEED CONTROL OF DC SHUNT MOTOR
Date :
Aim:
To vary the speed of the given dc shunt motor by the following methods.
(i). Armature control method (below rated speed)
(ii). Field control method (above rated speed)
Apparatus Required:
Sl. No Name of the apparatus Range Type Quantity
1. Ammeter (0-2) A M.C 1
2. Volt meter (0-300) V M.C 1
3. Tachometer (0-1500) rpm Analog/Digital 1
4. Rheostat300 / 1.4 A
100 / 4 AWire wound Each 1
5. Connecting wires Required
Precautions:
1. The field rheostat must be kept at minimum resistance position at the time of starting.
2. The armature rheostat must be kept at maximum resistance position at the time of
starting.
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Circuit Diagram:
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
+
-220
Volts
D.C
Supply
DPST
Switch
A1
A2
Fuse
Fuse
2 A
2 A
V
(0-300 V)
MC
Fuse Rating Calculation
10% of Rated Current
Motor =
F1
F2
300 /
1.4 A
(0-2.5 A)
MC
M V
100 / 4 A
Speed Control of DC
Shunt Motor
A
Model Graph:
(i) Armature Control method (ii) Field control method
Speed
(Rpm) Speed
(Rpm)
Armature voltage (volts) Field current (amps)
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Tabulations:
(i). Armature control method:
Field current (If) = ______ Amps kept constant
SL.
No
Armature voltage
(Volts)
Speed
(rpm)
(ii) Field control method
Armature voltage (Va) = ______ Volts kept constant
SL.
No
Field current
(Amps)
Speed
(rpm)
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Procedure:
(i). Armature control method:
Make the connections as per the circuit diagram
Switch on the supply
Keep the field current constant and for different armature voltage (by varying
armature rheostat) note down the corresponding speed.
Bring back the rheostat to initial position and switch off the supply
(ii). Field control method
Switch on the supply
Start the motor by closing the DPST switch
Keep the armature voltage constant and for various field current (by varying field
rheostat) note down the corresponding speed.
Bring back the rheostat to initial position and switch off the supply
Result:
Thus the speed of the given DC shunt motor is varied by both armature control
and field control method and the graphs are plotted. The speed is directly proportional to
the armature voltage by graph (i) and inversely proportional to the field current by graph
(ii).
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Ex. No: OC AND SC TEST OF SINGLE PHASE TRANSFORMER
Date :
Aim:
To perform open circuit and short circuit test on a single phase transformer and
predetermine the efficiency at various loads and also draw the equivalent circuit.
Apparatus Required:
Sl.No Name of the apparatus Range Type Quantity
1. Ammeter (0-2) A
(0-5) AMI Each 1
2. Volt meter (0-150) V
(0-30) VMI Each 1
3. Watt meter 150V, 2A, LPF
30V, 5A, UPFDynamo meter Each 1
4. 1- Autotransformer (0-270) V 1
5 Connecting wires Required
Formulae:
Transformer Ratings: 1 KVA, 220 V/ 110V, 50HZ
V1 = 220 V & V2 = 110 V
I 1 = 1000/220 = 4.55 A & I2 = 1000/110 = 9.09 A
K = V2 / V1 = 110/220 = 0.5
From open circuit test:
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In the open circuit test the primary is open circuited and the meters are connected on
L.V side, which is secondary of the transformer. Thus O.C test will give us no load
current, I01. (i.e referred to secondary)
Since K = V2/V1, the corresponding no load primary current, I0 = I01 * K
W0 = V1 I0 Cos 0 ( watts)
Where,
W0 = No load input power = core (or Iron) loss = Wi
I0 - No load input current
V1 - No load rated input voltageCos - Power factor
Cos 0 = W0 / V1 I0I w = I0 Cos 0 A ( Iron loss component)
I = I0 Sin 0 A ( Magnetizing component)
R0 = V1 / I w (Resistance to represent core loss)
X0 = V1 / I (Reactance to represent magnetizing component)
From short circuit test:
In the Short circuit test the secondary is short circuited and the meters are on H.V
side, which is primary of the transformer. Hence it gives parameters referred to primary.
R01 = Wsc / Isc2
Z01 = Vsc / Isc
X01 = Z012 - R012
I21 = I2 * K & I1 = I0 + I2
1
Where,
R01 - Equivalent resistance of transformer referred to primary side
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X01 - Equivalent reactance of transformer referred to primary side
Z01 - Equivalent impedance of transformer referred to primary side
Wsc Full load copper loss
Isc Short Circuit Current
Vsc Short circuit voltage corresponding to Isc
Equivalent Circuit Parameters referred to secondary side:
R01 = R0 * K
2 I01 = No load current from O.C Test
X01
= X0 * K2
I w1
= V11
/ R01
R02 = R01 x K2 I
1 = V11 / X0
1
X02 = X01 x K2 Where, V1
1 = V1 * K
Z02 = Z01 x K2 I1
1 = I01 + I2
Regulation = [ I2 R02 Cos + I2 X02 Sin / V2 ] X 100
+ Ve for lagging Power factor
- Ve for leading power factor
(X * KVA * P.f)
% Efficiency at various loads = x 100
[(X * KVA * P.f ) + (Wi + X 2 Wsc)]
X Load ratio
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Circuit Diagram:
DPSTSwitch
Fuse
230 V
1- 50 HZ
AC Supply V
A
C
M L
V
Fuse
5 A
5 A
(0-270 V) 1
AutoTrnsformer (0-150 V)MI
(0-2 A) MI
150 V, 2A, LPF
Wattmeter
110 V 220 V
Open Circuit
Name Plate Details
Single Phase Transformer
Auto TransformerFuse Rating Calculation
KVA________
Voltage Ratio________
20 % of Rated Current(Max. Load of A.T )
Maximum Load =
Maximum KVA =
Input =
0 V 0 V
Open Circuit Test on Single Phase Transformer
P
N
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Circuit Diagram:
DPST
Switch
Fuse
230 V1- 50 HZ
AC Supply V
A
C
M L
V
Fuse
5 A
5 A
(0-270 V) 1
Auto
Trnsformer
(0-30 V)
MI
(0-5 A) MI
30 V, 5A, UPF
Wattmeter
220 V 110 V
Fuse Rating Calculation
Short Circuit
0 V 0 V
Isc = KVA / V
= Short Circuit Test on Single Phase Tranformer
P
N
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Equivalent circuit referred to primary side:
V1
I21
I0
I1
IW I
X0R0
R01 X01
ZL1
V21
Equivalent circuit referred to secondary side:
V11
I11
I01
I2
IW1 I
1
X01R0
1
R02 X02
ZL
V2
Model Graph:
UPF
%Reg.
% 0.8
Leading P.F Lagging P.F
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O/P Power (Watts) %Reg.
Tabulations:
Open circuit test:
Short circuit test:
Sl.
No
Vo
(Volts)
Io
(Amps)
Wo
(Div)
Wo x M.F
(Watts)
Sl.
No
Vsc(Volts)
Isc(Amps)
Wsc(Div)
Wsc x M.F
(Watts)
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Tabulation for determine the Efficiency:
Sl.
No
Load
ratio
(X)
Output power
(Watts)
Wi(Watts)
Wcu(Watts)
Input Power
(Watts)
%
Efficiency
UPF 0.8 UPF 0.8 UPF 0.8
1
2
3
41
Tabulation for determine the Regulation:
Sl.No Power Factor (Cos )
% Regulation
Leading Lagging
1 0
2 0.2
3 0.4
4 0.6
5 0.8
6 1.0
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Precautions:
Autotransformer must be kept at minimum potential point during starting condition.
Procedure:
Open circuit test:
Make the connections as per the circuit diagram
Switch on the supply and vary the autotransformer to get rated voltage
Note down ammeter, voltmeter and wattmeter readings.
Bring back the autotransformer to original position.
Switch off the supply
Short circuit test:
Make the connections as per the circuit diagram
Switch on the supply and vary the autotransformer to get rated short circuit current.
Note down ammeter, voltmeter and wattmeter readings.
Bring back the autotransformer to original position.
Switch off the supply
Result:
Thus the open circuit and short circuit tests were performed on a single-phase
transformer and the efficiency was predetermined at various loads.
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Ex. No: LOAD TEST ON SINGLE PHASE TRANSFORMER
Date :
Aim:
To perform load test on a single phase transformer and determine its performance
characteristics
Apparatus Required:
Sl.no Name of the apparatus Range Type Quantity
1. Ammeter (0-5) A
(0-10) AMI Each 1
2. Volt meter (0-150) V
(0-300) VMI Each 1
3. Watt meter 150V, 5A, UPF
300V, 10 A, UPFDynamo meter Each 1
4. 1- Autotransformer (0-270) V 1
5 Connecting wires Required
Formulae:
Input power = W1 x M.F1 watts
Output power = W2 x M.F2 watts
% Efficiency = Output power / Input power X100
% Regulation = (E02 V2) / E02 x 100
E 02 - No load secondary voltage
V 2 - Secondary voltage at various loads
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M.F Multiplication factor
W1, W2 - Wattmeter readings
V I cos Multiplication factor (M.F) =
No of divisions in the watt meter
Precautions:
Autotransformer must be kept at minimum potential point during starting condition.
There should be no load at the time of starting the experiment
Procedure:
Make the connections as per the circuit diagram.
Switch on the supply and vary the autotransformer to get rated primary voltage.
Note down the no load readings.
Add the load in steps and note down all the meter readings till the rated secondarycurrent is reached.
Remove the load and bring back the autotransformer to original position.
Switch off the supply.
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Circuit Diagram:
DPST
Switch
Fuse
230 V1- 50
HZ AC
Supply
A
C
M L
V
Fuse
15 A
15 A
(0-270 V)
1 Auto
Trnsform
er
(0-150 V)
MI
(0-5 A) MI
150 V, 5A, UPF
Wattmeter
110 V 220 V
Fuse Rating Calculation
0 V 0 V
Load Test on Single Phase Tranformer
C
M L
V
A
DPST
Switch
Fuse
Fuse
10 A
10 A
(0-10 A) MI
300 V, 10A, UPF
V V(0-300 V)
MI
Wattmeter
Load
Name Plate Details
Primary Side Secondary Side
Power =
Voltage =
Current =
Power =
Voltage =
Current =
Primary Side: 125 % of Rated Current
=
Secondary Side: 125 % of Rated Current
=
P
N
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Tabulation:
Sl. Primary
Voltage
Primary Input Power Secondary
Voltage
Secondar Output PowerEfficiency Reg
W1 W1 X M.F W2 W2 X M.F
(Volts) (Amps) (Div) (Watts) (Volts) (Amps)(Div
(Watts) %
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Ex. No: SWINBURNES TEST(No load Test)
Date :
Aim:
To predetermine the efficiency of DC shunt machine at various load current while
operating as a motor and generator and plot a graph output Vs % efficiency.
Apparatus required:
Sl. No. Name Range Type Quantity
1 Voltmeter (0-300) V MC 1
2 Ammeter (0-2.5) A MC 2
3 Rheostat 300 / 1.4 A Wire wound 1
4 Tachometer Analog / Digital 15 Connecting wires Required
Formula:
Constant Losses WC = Input Power - No load Armature copper loss
= VIo Iao2X Ra
Where, Iao= Io - IfRa = Armature resistance
For motor:1. Ia = IL If Amps
2. Armature copper loss = Ia2 Ra watts
3. Total loss WT = WC +Ia2 Ra watts
4. Input power = V IL watts
5. Output Power = Input Power Total Loss watts
6. Efficiency % m = [Output Power / Input Power ] X 100 No unit
For Generator:
1. Ia = IL +If Amps
2. Armature copper loss = Ia2 Ra watts
3. Total loss WT = WC +Ia2 Ra watts
4. Output power = V IL watts
5. Input Power = Output Power + Total Loss watts
6. Efficiency % G = [Output Power / Input Power ] X 100 No unit
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Circuit Diagram:
Motor Name Plate Details
KW________
RPM________
Volts________
Amps________
+
-220
VoltsD.C
Supply
DPST
Switch
A1
A2
Fuse
Fuse
2 A
2 A
M
LF
A
F1
F2
3-Point Starter
300 /
1.4 A
A
A
V(0-300 V)
MC
(0-2.5 A)
MC
(0-2.5 A)MC
Fuse Rating Calculation
10% of Rated Current
Motor =
Swinburnes Test
Model graph:
%
Output (watts)Tabulation:
Sl. No V (volts) I0 (amp) If(amp)
Generator
Motor
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Motor:
Ra = _______ Ohms
Sl.
No
V
(volts)
IL(amp)
Ia=IL-If(amp)
Ia2Ra
_(watts)
WC
_(watts)
WT =WC+Ia2Ra
_(watts)
Input
VIL
_(watts)
Output
_(watts)%
Generator:
Ra = _______ Ohms
Sl. NoV
(volts)
IL(amp)
Ia=IL+I
f
(amp)
Ia2Ra
_(watts
)
WC
_(watts)
WT=WC+Ia
2Ra
_(watts)
Outpu
t
VIL
_(watt
s)
Input
_(watts)
%
Precautions:
1. The motor field rheostat should be kept at minimum resistance position.
Procedure:
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1. Connections are made as per the circuit diagram.
2. Observing the precaution the DPST switch is closed and the motor is started with
the help of 3-point DC starter slowly.
3. The motor field rheostat is adjusted and the motor is brought to rated speed.
4. The voltmeter and ammeter readings are noted down
5. Field rheostat is brought back to minimum position
6. Disconnect and return the meters.
Result:
The efficiency of the dc shunt machine was determined when it was running as a
generator as well as a motor.
43
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