LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE
TIRUNELVELI
CO
DEPARTMENT OF EEE
LAB MANUAL
: II YEAR EEE
: IV SEM
SUBJECT CODE
: EE6411
SUBJECT
: Electrical Machines I Lab
V
IE
R
EN
G
IN
EE
RI
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CLASS
SEMESTER
FR
A
N
CI
S
X
A
Prepared By
Mr.G.AravindKumar, AP/EEE
Mrs.Shanthi, AP/EEE
www.francisxavier.ac.in
SYLLABUS
EE6211—ELECTRICALMACHINES LABORATORY – I
To expose the students to the operation of D.C. machines and transformers and give
1.
LL
EG
them experimental skill.
Open circuit and load characteristics of separately and self excited DC shunt
CO
generators.
Load characteristics of DC compound generator with differential and
G
2.
RI
N
cumulative connection.
Load characteristics of DC shunt and compound motor.
4.
Load characteristics of DC series motor.
5.
Swinburne’s test and speed control of DC shunt motor.
6.
Hopkinson’s test on DC motor – generator set.
7.
Load test on single-phase transformer and three phase transformer
EN
G
IN
EE
3.
IE
R
connections.
E
AIM
Open circuit and short circuit tests on single phase transformer.
9.
Sumpner’s test on transformers.
10.
Separation of no-load losses in single phase transformer.
11.
Study of starters and 3-phase transformers connections
FR
A
N
CI
S
X
A
V
8.
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Ex.No.1
OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED
DC SHUNT GENERATOR
LL
EG
E
AIM:
To obtain open circuit characteristics of self excited DC shunt generator and to
find its critical resistance.
CO
APPARATUS REQUIRED:
Apparatus
Range
Type
Quantity
1
Ammeter
(0-1)A
MC
1
2
Voltmeter
(0-300)V
MC
3
Rheostats
1250, 0.8A
Wire Wound
2
4
SPST Switch
-
-
1
5
Tachometer
(0-1500)rpm
6
Connecting Wires
2.5sq.mm.
EE
RI
N
G
S.No.
1
1
Copper
Few
IN
Digital
G
PRECAUTIONS:
EN
1. The field rheostat of motor should be in minimum resistance position at the time
of starting and stopping the machine.
R
2. The field rheostat of generator should be in maximum resistance position at the
IE
time of starting and stopping the machine.
X
PROCEDURE:
A
V
3. SPST switch is kept open during starting and stopping.
S
1. Connections are made as per the circuit diagram.
N
CI
2. After checking minimum position of motor field rheostat, maximum position of
generator field rheostat, DPST switch is closed and starting resistance is
FR
A
gradually removed.
3. By adjusting the field rheostat, the motor is brought to rated speed.
4. Voltmeter and ammeter readings are taken when the SPST switch is kept open.
5. After closing the SPST switch, by varying the generator field rheostat, voltmeter
and ammeter readings are taken.
6. After bringing the generator rheostat to maximum position, field rheostat of motor
to minimum position, SPST switch is opened and DPST switch is opened.
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FR
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V
A
X
G
RI
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EE
IN
G
EN
CO
LL
EG
E
S.N
Armature
Current
Voltage
If (Amps)
Eo (Volts)
RI
N
G
CO
LL
EG
o.
Field
E
TABULAR COLUMN:
IN
Eo (Volts)
EE
MODEL GRAPH:
EN
G
Critical Resistance = Eo / If Ohms
R
If
If (Amps)
RESULT:
X
A
V
IE
Eo
N
CI
S
Thus open circuit characteristics of self excited DC shunt generator are obtained and its
FR
A
critical resistance is determined.
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Ex.No.2
LOAD CHARACTERISTICS OF SELF EXCITED
E
DC SHUNT GENERATOR
To obtain internal and external characteristics of DC shunt generator.
APPARATUS REQUIRED:
Type
(0-2)A
MC
(0-20) A
MC
Voltmeter
(0-300)V
MC
3
Rheostats
1200, 0.8A
4
Loading Rheostat
5KW, 230V
5
Tachometer
(0-1500)rpm
Digital
1
6
Connecting Wires
2.5sq.mm.
Copper
Few
G
2
1
RI
N
Ammeter
1
1
Wire Wound
2
-
1
EE
1
Quantity
CO
Range
IN
Apparatus
G
S.No.
LL
EG
AIM:
EN
PRECAUTIONS:
1. The field rheostat of motor should be at minimum position.
R
2. The field rheostat of generator should be at maximum position.
IE
3. No load should be connected to generator at the time of starting and stopping.
V
PROCEDURE:
X
A
1. Connections are made as per the circuit diagram.
2. After checking minimum position of DC shunt motor field rheostat and maximum position of
S
DC shunt generator field rheostat, DPST switch is closed and starting resistance is
N
CI
gradually removed.
FR
A
3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the
voltage to rated voltage by adjusting the field rheostat of generator.
4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted.
5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to
maximum position and the field rheostat of DC shunt motor to minimum position, DPST
switch is opened.
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S
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A
FR
R
IE
V
A
X
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RI
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EE
IN
G
EN
CO
LL
EG
E
DETERMINATION OF ARMATURE RESISTANCE:
Fuse
+
+
E
LL
EG
S
W
I
T
C
H
(0-20)A
MC
A1
+
V (0-300)V
MC
-
G
A2
LOAD
5 KW, 230V
27A
RI
N
-
CO
220V
DC
Supply
27A
G
D
P
S
T
-
A
Fuse
EE
PROCEDURE:
IN
1. Connections are made as per the circuit diagram.
2. Supply is given by closing the DPST switch.
G
3. Readings of Ammeter and Voltmeter are noted.
Current
Armature Resistance
V (Volts)
I (Amps)
Ra (Ohms)
Voltage
FR
A
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CI
S
X
S.No.
A
V
TABULAR COLUMN:
IE
R
EN
4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
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TABULAR COLUMN:
Load
Terminal
Current
Current
Voltage
If (Amps)
IL (Amps)
(V) Volts
Ia = I L + I f
Eg =V + Ia Ra
(Amps)
(Volts)
CO
LL
EG
E
S.No.
Field
G
FORMULAE:
=
V + Ia Ra (Volts)
Ia
=
IL + If (Amps)
Eg
:
Generated emf in Volts
V
:
Terminal Voltage in Volts
Ia
:
Armature Current in Amps
IL
:
Line Current in Amps
If
:
Field Current in Amps
Ra
:
Armature Resistance in Ohms
EN
G
IN
EE
RI
N
Eg
A
N
CI
S
X
A
V
VL, E (Volts)
IE
R
MODEL GRAPH:
E Vs IL
(Int Char)
V Vs IL
(Ext Char)
FR
If, IL (Amps)
RESULT:
Thus the load characteristics of self excited DC shunt generator is obtained.
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Ex.No.3
OPEN CIRCUIT CHARACTERISTICS OF SEPARATELY EXCITED
DC SHUNT GENERATOR
LL
EG
E
AIM:
To obtain open circuit characteristics of separately excited DC shunt generator.
APPARATUS REQUIRED:
Apparatus
Range
Type
Quantity
1
Ammeter
(0-1)A
MC
2
Voltmeter
(0-300)V
MC
3
Rheostats
1250, 0.8A
Wire Wound
4
Tachometer
(0-1500)rpm
5
Connecting Wires
2.5sq.mm.
CO
S.No.
1
RI
N
G
1
2
1
Copper
Few
EE
Digital
IN
PRECAUTIONS:
1. The field rheostat of motor should be in minimum resistance position at the time of starting
G
and stopping the machine.
EN
2. The field rheostat of generator should be in maximum resistance position at the time of
R
starting and stopping the machine.
IE
PROCEDURE:
V
1. Connections are made as per the circuit diagram.
A
2. After checking minimum position of motor field rheostat, maximum position of generator
X
field rheostat, DPST switch is closed and starting resistance is gradually removed.
S
3. By adjusting the field rheostat, the motor is brought to rated speed.
N
CI
4. By varying the generator field rheostat, voltmeter and ammeter readings are taken.
5. After bringing the generator rheostat to maximum position, field rheostat of motor to
FR
A
minimum position, DPST switch is opened.
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A
FR
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V
A
X
G
RI
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EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
Field Current
Armature Voltage
If (Amps)
Eo (Volts)
RI
N
G
CO
LL
EG
E
S.No.
If (Amps)
V
IE
R
EN
G
IN
Eo (Volts)
EE
MODEL GRAPH:
A
RESULT:
FR
A
N
CI
S
X
Thus open circuit characteristics of separately excited DC shunt generator is obtained.
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Ex.No.4
LOAD CHARACTERISTICS OF SEPARATELY EXCITED
E
DC SHUNT GENERATOR
LL
EG
AIM:
To obtain internal and external characteristics of DC separately excited DC shunt
generator.
Apparatus
Type
(0-2)A
MC
(0-20) A
MC
Quantity
1
Ammeter
2
Voltmeter
(0-300)V
3
Rheostats
1200, 0.8A
4
Loading Rheostat
5KW, 230V
-
1
5
Tachometer
(0-1500)rpm
Digital
1
6
Connecting Wires
2.5sq.mm.
Copper
Few
G
S.No.
RI
N
Range
CO
APPARATUS REQUIRED:
1
1
Wire Wound
2
EE
MC
EN
G
IN
1
PRECAUTIONS:
R
1. The field rheostat of motor should be at minimum position.
IE
2. The field rheostat of generator should be at maximum position.
A
X
PROCEDURE:
V
3. No load should be connected to generator at the time of starting and stopping.
1. Connections are made as per the circuit diagram.
S
2. After checking minimum position of DC shunt motor field rheostat and maximum position of
N
CI
DC shunt generator field rheostat, DPST switch is closed and starting resistance is
gradually removed.
FR
A
3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the
voltage to rated voltage by adjusting the field rheostat of generator.
4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted.
5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to
maximum position and the field rheostat of DC shunt motor to minimum position, DPST
switch is opened.
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S
N
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A
FR
R
IE
V
A
X
G
RI
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EE
IN
G
EN
CO
LL
EG
E
DETERMINATION OF ARMATURE RESISTANCE:
Fuse
+
+
S
W
I
T
C
H
E
(0-20)A
MC
A1
LL
EG
220V
DC
Supply
27A
+
V (0-300)V
MC
-
G
A2
CO
D
P
S
T
-
A
LOAD
5 KW, 230V
27A
Fuse
PROCEDURE:
IN
2. Supply is given by closing the DPST switch.
EE
1. Connections are made as per the circuit diagram.
RI
N
G
-
3. Readings of Ammeter and Voltmeter are noted.
IE
Voltage
Current
Armature Resistance
A
S.No.
V
TABULAR COLUMN:
R
EN
G
4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
I (Amps)
Ra (Ohms)
FR
A
N
CI
S
X
V (Volts)
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TABULAR COLUMN:
Load
Terminal
Current
Current
Voltage
If (Amps)
IL (Amps)
(V) Volts
Ia = I L + I f
Eg =V + Ia Ra
(Amps)
(Volts)
CO
LL
EG
E
S.No.
Field
G
FORMULAE:
=
V + Ia Ra (Volts)
Ia
=
IL + If (Amps)
Eg
:
Generated emf in Volts
V
:
Terminal Voltage in Volts
Ia
:
Armature Current in Amps
IL
:
Line Current in Amps
If
:
Field Current in Amps
Ra
:
Armature Resistance in Ohms
EN
G
IN
EE
RI
N
Eg
E Vs IL
(Int Char)
V Vs IL
(Ext Char)
FR
A
N
CI
S
X
A
V
VL, E (Volts)
IE
R
MODEL GRAPH:
If, IL (Amps)
RESULT:
Thus load characteristics of separately excited DC shunt generator is obtained.
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Ex.No.5
LOAD TEST ON DC SHUNT MOTOR
AIM:
APPARATUS REQUIRED:
LL
EG
E
To conduct load test on DC shunt motor and to find efficiency.
Apparatus
Range
Type
Quantity
1
Ammeter
(0-20)A
MC
1
2
Voltmeter
(0-300)V
MC
3
Rheostat
1250, 0.8A
Wire Wound
1
4
Tachometer
(0-1500) rpm
Digital
1
5
Connecting Wires
2.5sq.mm.
CO
S.No.
RI
N
G
1
Few
EE
Copper
PRECAUTIONS:
IN
1. DC shunt motor should be started and stopped under no load condition.
G
2. Field rheostat should be kept in the minimum position.
EN
3. Brake drum should be cooled with water when it is under load.
PROCEDURE:
IE
R
1. Connections are made as per the circuit diagram.
2. After checking the no load condition, and minimum field rheostat position, DPST switch is
V
closed and starter resistance is gradually removed.
A
3. The motor is brought to its rated speed by adjusting the field rheostat.
X
4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load
S
condition.
N
CI
5. The load is then added to the motor gradually and for each load, voltmeter, ammeter,
spring balance readings and speed of the motor are noted.
DPST switch is opened.
FR
A
6. The motor is then brought to no load condition and field rheostat to minimum position, then
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S
N
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A
FR
R
IE
V
A
X
G
RI
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EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
Voltage
V
(Volts)
Spring Balance
Reading
S1(Kg)
(S1 S2)Kg
S2(Kg)
Speed
N
(rpm)
Torque
T
(Nm)
Output
Power
Pm
(Watts
)
Input
Power
Pi
(Watts)
Efficiency
%
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
S.No.
Current
I
(Amps)
V
IE
Circumference of the Brake drum
X
A
FORMULAE:
Circumference
------------------- m
S
=
N
CI
R
100 x2
FR
A
Torque T = (S1  S2) x R x 9.81 Nm
Input Power Pi = VI Watts
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=
cm.
2NT
Output Power Pm = ------------ Watts
60
Efficiency  %
E
Output Power
LL
EG
= -------------------- x 100%
Input Power
EE
Speed N (rpm)
y
RI
N

N
G
y1
Speed N (rpm)
y2
Torque T (Nm)
Efficiency %
y3
CO
MODEL GRAPHS:
EN
G
IN
T
x
Torque T (Nm)
IE
R
Output Power (Watts)
V
RESULT:
FR
A
N
CI
S
X
A
Thus load test on DC shunt motor is conducted and its efficiency is determined.
www.francisxavier.ac.in
Ex.No.6
LOAD TEST ON DC COMPOUND MOTOR
AIM:
APPARATUS REQUIRED:
LL
EG
E
To conduct load test on DC compound motor and to find its efficiency.
Apparatus
Range
Type
Quantity
1
Ammeter
(0-20)A
MC
1
2
Voltmeter
(0-300)V
MC
3
Rheostat
1250, 0.8A
Wire Wound
1
4
Tachometer
(0-1500) rpm
Digital
1
5
Connecting Wires
2.5sq.mm.
CO
S.No.
RI
N
G
1
Few
EE
Copper
PRECAUTIONS:
IN
1. DC compound motor should be started and stopped under no load condition.
G
2. Field rheostat should be kept in the minimum position.
EN
3. Brake drum should be cooled with water when it is under load.
PROCEDURE:
IE
R
1. Connections are made as per the circuit diagram.
2. After checking the no load condition, and minimum field rheostat position, DPST switch
V
is closed and starter resistance is gradually removed.
A
3. The motor is brought to its rated speed by adjusting the field rheostat.
X
4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no
S
load condition.
N
CI
5. The load is then added to the motor gradually and for each load, voltmeter, ammeter,
spring balance readings and speed of the motor are noted.
then DPST switch is opened.
FR
A
6. The motor is then brought to no load condition and field rheostat to minimum position,
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
FORMULAE:
Output
Speed Torque
Power
N
T
Pm
(rpm) (Nm)
(Watts)
Input
Power Efficiency
Pi
%
(Watts)
E
(S1
S2)Kg
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
Spring Balance
Voltage Current
Reading
S.No. V
I
(Volts) (Amps) S1(Kg)
S2(Kg)
Circumference
=
------------------- m
X
A
100 x2
V
R
N
CI
S
Torque T = (S1  S2) x R x 9.81 Nm
FR
A
Input Power Pi = VI Watts
2NT
Output Power Pm = ------------ Watts
60
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Output Power
Efficiency  %
= -------------------- x 100%
Input Power
MODEL GRAPHS:

IN
RESULT:
G
EE
Output Power (Watts)
RI
N
T
CO
y
Speed N (rpm)
N
LL
EG
E
y1
Speed N (rpm)
y2
Torque T (Nm)
Efficiency %
y3
Torque T (Nm)
FR
A
N
CI
S
X
A
V
IE
R
EN
G
Thus load test on DC compound motor is conducted and its efficiency is determined.
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x
Ex.No.7
E
LOAD CHARACTERISTICS OF DC COMPOUND GENERATOR
LL
EG
AIM:
To obtain the load characteristics of DC Compound generator under cumulative and
differential mode condition.
Apparatus
Type
(0-2)A
MC
(0-20) A
MC
Quantity
1
Ammeter
2
Voltmeter
(0-300)V
3
Rheostats
1200, 0.8A
4
Loading Rheostat
5KW, 230V
-
1
5
Tachometer
(0-1500)rpm
Digital
1
6
Connecting Wires
2.5sq.mm.
Copper
Few
G
S.No.
RI
N
Range
CO
APPARATUS REQUIRED:
1
1
Wire Wound
2
EE
MC
EN
G
IN
1
PRECAUTIONS:
R
1. The field rheostat of motor should be at minimum position.
IE
2. The field rheostat of generator should be at maximum position.
3. No load should be connected to generator at the time of starting and stopping.
V
PROCEDURE:
X
A
1. Connections are made as per the circuit diagram.
2. After checking minimum position of DC shunt motor field rheostat and maximum
S
position of DC shunt generator field rheostat, DPST switch is closed and starting
N
CI
resistance is gradually removed.
FR
A
3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the
voltage to rated voltage by adjusting the field rheostat of generator.
4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted.
5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought
to maximum position and the field rheostat of DC shunt motor to minimum position,
DPST switch is opened.
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6. The connections of series field windings are reversed the above steps are repeated.
7. The values of voltage for the particular currents are compared and then the differential
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
and cumulative compounded DC generator is concluded accordingly.
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TABULAR COLUMN:
Cumulatively Compounded
Differentially Compounded
V (Volts)
V (Volts)
S.No.
IL (Amps)
G
CO
LL
EG
E
IL (Amps)
IN
EE
Cumulatively Compounded
RI
N
V (Volts)
MODEL GRAPH:
R
EN
G
Differentially Compounded
V
IE
IL (Amps)
A
RESULT:
X
Thus load characteristics of DC compound generator under cumulative and differential
FR
A
N
CI
S
mode condition are obtained
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Ex.No.8
LOAD TEST ON DC SERIES MOTOR
AIM:
S.No.
Apparatus
Range
Type
Quantity
1
Ammeter
(0-20)A
MC
1
2
Voltmeter
(0-300)V
MC
CO
APPARATUS REQUIRED:
LL
EG
E
To conduct load test on DC Series Motor and to find efficiency.
3
Tachometer
Digital
1
4
Connecting Wires
Copper
Few
EE
2.5sq.mm.
G
rpm
RI
N
(0-3000)
1
PRECAUTIONS:
IN
1. The motor should be started and stopped with load
EN
G
2. Brake drum should be cooled with water when it is under load.
PROCEDURE:
1. Connections are made as per the circuit diagram.
R
2. After checking the load condition, DPST switch is closed and starter resistance is gradually
IE
removed.
V
3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings are
A
noted.
FR
A
N
CI
S
X
4. After bringing the load to initial position, DPST switch is opened.
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
(S1
S2)Kg
Output
Speed Torque
Power
N
T
Pm
(rpm) (Nm)
(Watts)
Input
Power Efficiency
Pi
%
(Watts)
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
Spring Balance
Voltage Current
Reading
S.No. V
I
(Volts) (Amps) S1(Kg)
S2(Kg)
V
FORMULAE:
=
------------------- m
X
R
A
Circumference
S
100 x2
N
CI
Torque T = (S1  S2) x R x 9.81 Nm
FR
A
Input Power Pi = VI Watts
2NT
Output Power Pm = ------------ Watts
60
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Output Power
Efficiency  %
= -------------------- x 100%
Input Power
LL
EG
y1
T
Speed N (rpm)
CO
E
G
y2
Torque T (Nm)
Efficiency %
y3
E
MODEL GRAPH:
IN
Output Power (Watts)
EE
RI
N
N
G
RESULT:
FR
A
N
CI
S
X
A
V
IE
R
EN
Thus load test on DC series motor is conducted and its efficiency is determined.
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Ex. No. 9
SWINBURNE’S TEST
AIM:
To conduct Swinburne’s test on DC machine to determine efficiency when working as
LL
EG
E
generator and motor without actually loading the machine.
APPARATUS REQUIRED:
Apparatus
Range
Type
Quantity
1
Ammeter
(0-20) A
MC
1
2
Voltmeter
(0-300) V
MC
1
3
Rheostats
1250, 0.8A
4
Tachometer
(0-3000) rpm
5
Resistive Load
5KW,230V
-
1
6
Connecting Wires
2.5sq.mm.
Copper
Few
Wound
EE
Digital
1
1
G
IN
G
RI
N
Wire
CO
S.No.
EN
PRECAUTIONS:
The field rheostat should be in the minimum position at the time of starting and stopping
IE
R
the motor
PROCEDURE:
V
1. Connections are made as per the circuit diagram.
A
2. After checking the minimum position of field rheostat, DPST switch is closed and starting
X
resistance is gradually removed.
S
3. By adjusting the field rheostat, the machine is brought to its rated speed.
N
CI
4. The armature current, field current and voltage readings are noted.
FR
A
5. The field rheostat is then brought to minimum position DPST switch is opened.
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMNS:
IL
(Amps)
Ia
(Amps)
Ia Ra
(Watts)
Output
Power
(Watts)
Input
Efficiency
Power
%
(Watts)
LL
EG
V
(Volts)
Total
Losses
W
(Watts)
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
RI
N
G
CO
S. No.
2
www.francisxavier.ac.in
E
AS MOTOR:
AS GENERATOR:
V
(Volts)
I1
(Amps)
Ia
(Amps)
Total
Losses
(Watts)
Ia2Ra
(Watts)
Output
Power
(Watts)
Input
Efficiency
Power
%
(Watts)
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
S.
No.
R
TABULAR COLUMN:
If
Io
V
(Amps) (Amps) (Volts)
FR
A
N
CI
S
X
A
V
IE
S.No.
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DETERMINATION OF ARMATURE RESISTANCE:
Fuse
+
+
S
W
I
T
C
H
E
(0-20)A
MC
A1
LL
EG
220V
DC
Supply
27A
+
V (0-300)V
MC
-
M
A2
CO
D
P
S
T
-
A
LOAD
5 KW, 230V
27A
Fuse
PROCEDURE:
IN
2. Supply is given by closing the DPST switch.
EE
1. Connections are made as per the circuit diagram.
RI
N
G
-
3. Readings of Ammeter and Voltmeter are noted.
EN
G
4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
Voltage
IE
S.No.
R
TABULAR COLUMN:
Armature Resistance
I (Amps)
Ra (Ohms)
N
CI
S
X
A
V
V (Volts)
Current
FORMULAE:
FR
A
Hot Resistance Ra = 1.2 X R Ω
Constant losses
Where Iao
= VIo – Iao2 Ra watts
= (Io – If) Amps
AS MOTOR:
Load Current IL
= _____ Amps (Assume 15%, 25%, 50%, 75% of
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rated current)
Armature current Ia = IL – If Amps
= Ia2 Ra watts
Total losses
= Copper loss + Constant losses
Input Power
= VIL watts
Output Power
= Input Power – Total losses
LL
EG
E
Copper loss
Output power
Efficiency %
=
---------------------- X 100%
CO
Input Power
AS GENERATOR:
= _____ Amps (Assume 15%, 25%, 50%, 75% of
G
Load Current IL
RI
N
rated current)
Armature current Ia = IL + If Amps
= Ia2 Ra watts
Total losses
= Copper loss + Constant losses
Output Power
= VIL watts
Input Power
= Input Power +Total losses
G
Output power
IN
EE
Copper loss
Efficiency %
EN
= ----------------------- X 100%
Input Power
As a Generator
V
IE
R
MODEL GRAPH:
As a Motor
A
N
CI
S
X
A
%η
FR
OUTPUT POWER P0
(W)
RESULT:
Thus the efficiency of the D.C machine is predetermined by Swinburne’s test.
www.francisxavier.ac.in
Ex.No. 10
SPEED CONTROL OF DC SHUNT MOTOR
AIM:
To obtain speed control of DC shunt motor by
LL
EG
E
a. Varying armature voltage with field current constant.
b. Varying field current with armature voltage constant
APPARATUS REQUIRED:
Apparatus
Range
Type
Quantity
1
Ammeter
(0-20) A
MC
1
2
Voltmeter
(0-300) V
MC
1
3
Rheostats
1250, 0.8A
Wire
Tachometer
(0-3000) rpm
5
Connecting Wires
2.5sq.mm.
G
Wound
Digital
EE
4
RI
N
50, 3.5A
CO
S.No.
1
Few
IN
Copper
Each 1
G
PRECAUTIONS:
EN
1. Field Rheostat should be kept in the minimum resistance position at the time of starting
and stopping the motor.
R
2. Armature Rheostat should be kept in the maximum resistance position at the time of
IE
starting and stopping the motor.
V
PROCEDURE:
A
1. Connections are made as per the circuit diagram.
X
2. After checking the maximum position of armature rheostat and minimum position of field
S
rheostat, DPST switch is closed
N
CI
(i) Armature Control:
1. Field current is fixed to various values and for each fixed value, by varying the armature
A
rheostat, speed is noted for various voltages across the armature.
FR
(ii) Field Control:
1. Armature voltage is fixed to various values and for each fixed value, by adjusting
the field rheostat, speed is noted for various field currents.
2. Bringing field rheostat to minimum position and armature rheostat to maximum
position DPST switch is opened.
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
(i) Armature Voltage Control:
If3 =
Armature
Speed
Armature
Speed
Armature
Speed
Voltage
N (rpm)
Voltage
N (rpm)
Voltage
N (rpm)
Va ( Volts)
Va ( Volts)
G
CO
Va ( Volts)
LL
EG
S.No.
If2 =
Va1 =
Va3 =
Speed
Field
Speed
Current
N (rpm)
Current
N (rpm)
If (A)
Field
Speed
Current
N (rpm)
If (A)
V
If1
If3
S
X
A
If2
A
N
CI
Speed N (rpm)
MODEL GRAPHS:
Speed N (rpm)
IE
R
EN
G
If (A)
EE
Field
IN
S.No.
Va2 =
RI
N
(ii) Field Control:
FR
Va1
Va3 Va2
If (Amps)
Va (Volts)
RESULT:
Thus the speed control of DC Shunt Motor is obtained using Armature and Field control
methods.
www.francisxavier.ac.in
E
If1 =
Ex.No. 11
HOPKINSON’S TEST
AIM:
To conduct Hopkinson’s test on a pair of identical DC machines to pre-determine the
APPARATUS REQUIRED:
Apparatus
Range
Type
Quantity
1
Ammeter
(0-1)A
MC
1
(0-20) A
MC
2
2
Voltmeter
(0-300) V
MC
1
(0-600)V
MC
3
Rheostats
1250, 0.8A
4
Tachometer
(0-3000) rpm
Digital
1
5
Resistive Load
5KW,230V
-
1
6
Connecting Wires
2.5sq.mm.
Copper
Few
RI
N
G
CO
S.No.
LL
EG
E
efficiency of the machine as generator and as motor.
Wire
2
G
IN
EE
Wound
1
EN
PRECATUIONS:
1. The field rheostat of the motor should be in the minimum position at the time of starting
and stopping the machine.
IE
R
2. The field rheostat of the generator should be in the maximum position at the time of
starting and stopping the machine.
A
PROCEDURE:
V
3. SPST switch should be kept open at the time of starting and stopping the machine.
X
1. Connections are made as per the circuit diagram.
S
2. After checking the minimum position of field rheostat of motor, maximum position of
N
CI
field rheostat of generator, opening of SPST switch, DPST switch is closed and starting
resistance is gradually removed.
FR
A
3. The motor is brought to its rated speed by adjusting the field rheostat of the motor.
4. The voltmeter V1 is made to read zero by adjusting field rheostat of generator and SPST
switch is closed.
5. By adjusting field rheostats of motor and generator, various Ammeter readings,
voltmeter readings are noted.
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6. The rheostats and SPST switch are brought to their original positions and DPST switch
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
is opened.
www.francisxavier.ac.in
TABULAR COLUMN:
Stray
Loss
Per
M/c
w/2
(watts)
E
Total
Generator
Stray
Armature
losses
Cu Loss
W
W(watts)
(watts)
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
Motor
Supply
Armature
I2
I3
I4
I1 + I2
S.No. Voltage I1
Cu Loss
V(Volts) (Amps) (Amps) (Amps) (Amps) (Amps)
W (watts)
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AS MOTOR:
LL
EG
E
Total
Output Input
Efficiency
Losses
Power Power
W
%
(Watts) (Watts)
(Watts)
RI
N
G
CO
Motor
Armature
Field
stray
I
I
Cu Loss
2
3
V
I1
Loss
losses
S.No.
(Volts) (Amps) (Amps) (Amps) W
(Watts)
/2(Watts)
(Watts)
s)
Total
Losses
W
(Watts
)
IN
Stray
losses
/2(Wat
ts)
G
I1
(Amp
s)
Field
Loss
(Watts)
EN
V
S.No. (Volts
)
I2
(Amp
Motor
Armat
ure
Cu
Loss
W
EE
AS GENERATOR:
FR
A
N
CI
S
X
A
V
IE
R
(Watts)
www.francisxavier.ac.in
Output
Input
Power
Power
(Watts
(Watts)
)
Efficiency
%
www.francisxavier.ac.in
S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Supply is given by closing the DPST switch.
E
3. Readings of Ammeter and Voltmeter are noted.
TABULAR COLUMN:
Current
Armature Resistance
V (Volts)
I (Amps)
Ra (Ohms)
CO
Voltage
R
EN
G
IN
EE
RI
N
G
S.No.
LL
EG
4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
V
Input Power
IE
FORMULAE:
= VI1 watts
= (I1+ I2)2 Ra watts
Generator armature cu loss
= I22 Ra watts
Total Stray losses W
= V I1 - (I1+I2)2 Ra + I22 Ra watts.
Stray loss per machine
= W/2 watts.
N
CI
S
X
A
Motor armature cu loss
FR
A
AS MOTOR:
Input Power
= Armature input + Shunt field input
= (I1+ I2) V + I3V = (I1+I2+I3) V
Total Losses
= Armature Cu loss + Field loss + stray loss
= (I1 + I2)2 Ra + VI3 + W/2 watts
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Input power – Total Losses
Efficiency %
= ------------------------------------- x 100%
Input Power
= VI2 watts
Total Losses
= Armature Cu loss+ Field Loss + Stray loss
= I22 Ra + VI4 + W/2 watts
Output power
Efficiency %
Output Power+ Total Losses
RI
N
G
MODEL GRAPH:
CO
= -------------------------------------- x 100%
LL
EG
Output Power
EE
As a Generator
%η
R
EN
G
IN
As a Motor
X
A
V
IE
OUTPUT POWER P0 (W)
RESULT:
FR
A
N
CI
S
Thus Hopkinson’s test is conducted on a pair of identical DC machines the efficiency of the
machine as generator and as motor are pre-determined
www.francisxavier.ac.in
E
AS GENERATOR:
Ex.No. 12
LOAD TEST ON A SINGLE PHASE TRANSFORMER
LL
EG
To conduct load test on single phase transformer and to find efficiency and percentage
regulation.
APPARATUS REQUIRED:
2
Voltmeter
3
Wattmeter
4
Quantity
(0-10)A
MI
1
(0-5) A
MI
1
(0-150)V
MI
(0-300) V
(300V, 5A)
CO
Ammeter
Type
G
1
Range
RI
N
Apparatus
1
MI
1
Upf
1
EE
S.No.
Upf
1
Auto Transformer
1, (0-260)V
-
1
5
Resistive Load
5KW, 230V
-
1
6
Connecting Wires
Copper
Few
G
IN
(150V, 5A)
EN
2.5sq.mm
E
AIM:
R
PRECAUTIONS:
IE
1. Auto Transformer should be in minimum position.
A
PROCEDURE:
V
2. The AC supply is given and removed from the transformer under no load condition.
X
1. Connections are made as per the circuit diagram.
S
2. After checking the no load condition, minimum position of auto transformer and DPST
N
CI
switch is closed.
FR
A
3. Ammeter, Voltmeter and Wattmeter readings on both primary side and secondary side are
noted.
4. The load is increased and for each load, Voltmeter, Ammeter and Wattmeter readings on
both primary and secondary sides are noted.
5. Again no load condition is obtained and DPST switch is opened.
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
E
Output
Efficiency
Power
%

W2 x
Regulation
%
MF
V
IE
R
EN
G
IN
EE
RI
N
G
CO
Secondary
LL
EG
Input
Power
S.No. Load V1
I1
W1
V2
I2
W2
W1 x
(Volts) (Amps) (Watts) (Volts) (Amps) (Watts) MF
Primary
A
FORMULAE:
X
Output Power = W 2 x Multiplication factor
N
CI
S
Input Power = W 1 x Multiplication factor
= -------------------- x 100%
Input Power
VNL - VFL (Secondary)
FR
A
Efficiency  %
Output Power
Regulation R % = ------------------------------ x 100%
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VNL
MODEL GRAPHS:
R
G
CO
LL
EG
E
Regulation R %
Efficiency  %

RI
N
Output Power (Watts)
RESULT:
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
Thus the load test on single phase transformer is conducted.
www.francisxavier.ac.in
Ex.No. 13
OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE
TRANSFORMER
E
AIM:
LL
EG
To predetermine the efficiency and regulation of a transformer by conducting open circuit
test and short circuit test and to draw equivalent circuit.
APPARATUS REQUIRED:
Ammeter
2
Voltmeter
3
Wattmeter
4
Connecting Wires
Type
(0-2)A
MI
(0-5) A
MI
(0-150)V
MI
(150V, 5A)
1
2
1
UPF
1
Copper
Few
IN
2.5sq.mm
1
LPF
EE
(150V, 5A)
Quantity
CO
1
Range
G
Apparatus
RI
N
S.No.
G
PRECAUTIONS:
EN
1. Auto Transformer should be in minimum voltage position at the time of closing & opening
DPST Switch.
IE
OPEN CIRCUIT TEST:
R
PROCEDURE:
1. Connections are made as per the circuit diagram.
V
2. After checking the minimum position of Autotransformer, DPST switch is closed.
A
3. Auto transformer variac is adjusted get the rated primary voltage.
X
4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.
S
5. Auto transformer is again brought to minimum position and DPST switch is opened.
N
CI
SHORT CIRCUIT TEST:
1. Connections are made as per the circuit diagram.
FR
A
2. After checking the minimum position of Autotransformer, DPST switch is closed.
3. Auto transformer variac is adjusted get the rated primary current.
4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.
5. Auto transformer is again brought to minimum position and DPST switch is opened.
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
www.francisxavier.ac.in
S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
Io
Wo
(Volts)
(Amps)
(Watts)
Vsc
Isc
Wsc
(Volts)
(Amps)
(Watts)
CO
LL
EG
Vo
E
OPEN CIRCUIT TEST:
G
IN
EE
RI
N
G
SHORT CIRCUIT TEST:
EN
FORMULAE:
R
Core loss: W o = VoIo cos o
IE
Wo
A
V o Io
o = cos-1
V
cos o = -------
Wo
------V o Io
I = Io sin o (Amps)
V0
Ro = ------- 
I
V0
Xo = ------- 
I
N
CI
S
X
I = Io cos o (Amps)
Xo2 = ( Zo2 - Ro22)1/2
FR
A
Vsc
Zo2 = ------- 
Isc
Wsc
Ro2 = ------- 
Isc2
R02
Ro1 = ------- 
K2
X02
Xo1 = ------- 
K2
V2
K= ------- = 2
V1
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Percentage Efficiency:
for all loads and p.f.
(X) x KVA rating x 1000 x cos 
Output Power
Efficiency % = -------------------- = ------------------------------------------------
E
Output power + losses
(X) x KVA rating x 1000 x cos 
= -------------------------------------------------------------
CO
(X) x KVA rating x 1000 x cos  + W o + X2W sc
LL
EG
Input Power
G
Percentage Regulation:
RI
N
(X) x Isc (Ro2 cos   Xo2sin ) x 100 + = lagging
- = leading
R% = --------------------------------------
EE
V2
IN
Where X is the load and it is 1 for full load, ½ for half load, ¾ load, ¼ load etc.. and the power
G
factor is, upf, o.8 p.f lag and 0.8 p.f lead
EN
EQUIVALENT CIRCUIT:
ISCo
R
Ro1
Io
L
O
A
D
X
A
V
IE
R
Xo1
FR
A
N
CI
S
Vo
Ro
Xo
N
www.francisxavier.ac.in
ZL = ZL/K2
CO
LL
EG
E
Efficiency %
MODEL GRAPHS:
Output power (Watts)
G
IN
EE
RI
N
G
% lagging
% leading
RESULT:
X
A
V
IE
R
EN
Power factor
N
CI
S
Thus the efficiency and regulation of a transformer is predetermined by conducting open
FR
A
circuit test and short circuit test and the equivalent circuit is drawn.
www.francisxavier.ac.in
Ex.No. 14
SUMPNER’S TEST
LL
EG
To predetermine the efficiency and regulation of a given single phase Transformer by
E
AIM :
conducting back-to-back test and also to find the parameters of the equivalent circuit.
CO
APPARATUS REQUIRED:
Name of the Apparatus
Auto Transformer
Range
(0-270) V
Type
-
2
Wattmeter
300 V, 10A
75 V, 5 A
LPF
UPF
1
1
3
Ammeter
(0-2) A
(0-20) A
MI
MI
1
1
4
Voltmeter
(0-75) V
(0-150) V
MI
MI
1
1
5
Connecting Wires
2.5sq.mm
Copper
Few
Quantity
2
EN
G
IN
EE
RI
N
G
S. No.
1
PRECAUTIONS:
1. Auto Transformer whose variac should be in zero position, before switching on the ac
IE
R
supply.
A
PROCEDURE:
V
2. Transformer should be operated under rated values.
X
1. Connections are made as shown in the circuit diagram.
S
2. Rated voltage of 110V is adjusted to get in voltmeter by adjusting the variac of the Auto
N
CI
Transformer which would be in zero before switching on the supply at the primary side.
3. The readings of voltmeter, ammeter and wattmeter are noted on the primary side.
FR
A
4. A voltmeter is connected across the secondary and with the secondary supply off i.e switch
S is kept open. The voltmeter reading is noted.
5. If the reading of voltmeter reads higher voltage, the terminals of any one of secondary coil
is interchanged in order that voltmeter reads zero.
6. The secondary is now switched on and SPST switch is closed with variac of auto
transformer is zero.
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7. After switching on the secondary the variac of transformer (Auto) is adjusted so that full
load rated secondary current flows.
8. Then the readings of wattmeter, Ammeter and voltmeter are noted.
9. The Percentage Efficiency and percentage regulation are calculated and equivalent circuit
FR
A
N
CI
S
X
A
V
IE
R
EN
G
IN
EE
RI
N
G
CO
LL
EG
E
is drawn.
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FORMULAE:
W1
Core loss of each transformer W o = ----- Watts
E
2
LL
EG
W2
Full load copper loss of each transformer Wc = ------ Watts.
Wo
Io
o = Cos-1 ---------
I1 = ---- A
Ro = V1 / Iw
Xo = V1 / Iμ
V2 = Vs/2 x A
EE
Iμ = I1 Cos
Ro2 = Wc / I22
IN
Iw = I1 Coso
2
RI
N
V 1 I1
EN
G
Xo2 =  Zo22 – Ro22
R
Copper loss at various loads = I22 Ro2
V
IE
PERCENTAGE REGULATION:
X
A
1. Upf : I2 / V (Ro2 Coso) X 100
N
CI
S
2. Lagging pf : I2 / V (Ro2 Coso + Xo2Sino) X 100
FR
A
3. Leading pf : I2 / V (Ro2 Coso - Xo2Sino) X 100
Output Power
G
Wo = V1I1 Cos o
CO
2
(1) Upf : 3Kw
(2) Pf : 3Kw Coso
Input Power = Output Power + Core loss + Cu loss
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Zo2 = V2 / I2
Output power
Efficiency % = -------------------------- X 100%
Input Power
ISCo
LL
EG
E
EQUIVALENT CIRCUIT:
Xo1
Ro1
Io
L
O
A
D
G
Vo
CO
R
Xo
RI
N
Ro
EE
N
Cos  = 1
Cos  = 0.8 Lag
Cos  = 0.8 Lead
X
A
V
IE
R
% Efficiency
Cos  = 1
Cos  = 0.8 (Lead &
Lag
% Regulation
EN
G
IN
MODEL GRAPHS:
Secondary Current (Amps)
N
CI
S
Secondary Current (Amps)
A
RESULT:
Thus the efficiency and regulation of a given single phase Transformer is carried out by
FR
conducting back-to-back test and the equivalent circuit parameters are found out.
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Ex.No. 15
SEPARATION OF NO LOAD LOSSES IN A SINGLE PHASE TRANSFORMER
AIM:
To separate the eddy current loss and hysteresis loss from the iron loss of single phase
APPARATUS REQUIRED:
LL
EG
E
transformer.
Name of the Apparatus
Range
Type
Quantity
1
Rheostat
1250Ω , 0.8A
Wire Wound
2
2
Wattmeter
300 V, 5A
LPF
3
Ammeter
(0-2) A
MC
4
Voltmeter
(0-300) V
MI
5
Connecting Wires
2.5sq.mm
CO
S. No.
1
RI
N
G
1
Few
EE
Copper
1
PRECAUTIONS:
IN
1. The motor field rheostat should be kept at minimum resistance position.
EN
G
2. The alternator field rheostat should be kept at maximum resistance position.
PROCEDURE:
1. Connections are given as per the circuit diagram.
IE
R
2. Supply is given by closing the DPST switch.
3. The DC motor is started by using the 3 point starter and brought to rated speed by
V
adjusting its field rheostat.
A
4. By varying the alternator filed rheostat gradually the rated primary voltage is applied to the
X
transformer.
S
5. The frequency is varied by varying the motor field rheostat and the readings of frequency
N
CI
are noted and the speed is also measured by using the tachometer.
6. The above procedure is repeated for different frequencies and the readings are tabulated.
initial position.
FR
A
7. The motor is switched off by opening the DPST switch after bringing all the rheostats to the
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S
N
CI
A
FR
R
IE
V
A
X
G
RI
N
EE
IN
G
EN
CO
LL
EG
E
TABULAR COLUMN:
S.No. Speed
N (rpm)
Frequency
Voltage
Wattmeter
Iron loss
Wi / f
f (Hz)
V (Volts)
reading
Wi (Watts)
Joules
G
CO
LL
EG
E
Watts
RI
N
FORMULAE USED:
1. Frequency, f =(P*NS) / 120 in Hz P = No.of Poles &
2. Hysteresis Loss W h = A * f in Watts
Ns = Synchronous speed in rpm.
A = Constant (obtained from graph)
EE
3. Eddy Current Loss W e = B * f2 in Watts B = Constant (slope of the tangent drawn to the
IN
curve)
4. Iron Loss Wi = W h + We in Watts
W i / f = A + (B * f)
G
Here the Constant A is distance from the origin to the point where the line cuts the Y- axis
Δ(Wi / f ) / Δf
R
EN
in the graph between W i / f and frequency f. The Constant B is
IE
MODEL GRAPH:
y
x
A
f
A
N
CI
S
X
A
V
Wf
FR
RESULT:
Thus separation of eddy current and hysteresis loss from the iron loss on a single-phase
transformer is conducted.
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