Mech EE6365 EE lab_manual

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KIT-KALAIGNARKARUNANIDHI INSTITUTE OF TECHNOLOGY
Anna University, Chennai
Regulation-2013
B.E. – MECHANICAL ENGINEERING
EE6365 – ELECTRICAL ENGINEERING LABORATORY
LABMANUAL
Staff Name : G.JAYABASKARAN, AP/EEE
Name of the Laboratory : ELECTRICAL ENGINEERING LABORATORY
Subject Code : EE 6365
Year/Semester : II / III
Branch : MECHANICAL ENGINEERING
STAFF INCHARGE HOD/EEE

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Anna University-Chennai Regulation-2013
EE6365 ELECTRICALENGINEERINGLABORATORY L T P C
0 0 3 2
OBJECTIVES:
• To validate the principles studied in theory by performing experiments in the laboratory.
LISTOFEXPERIMENTS
1. Load test on DC Shunt &DC Series motor
2. O.C.C &Load characteristics of DC Shunt and DC Series generator
3. Speed control of DC shunt motor (Armature, Field control)
4. Load test on single phase transformer
5. O.C&S.CTest on a single phase transformer
6. Regulation of an alternator by EMF&MMF methods.
7. V curves and inverted V curves of synchronous Motor
8. Load test on three phase squirrel cage Induction motor
9 .Speed control of three phase slip ring Induction Motor
10 .Load test on single phase Induction Motor.
11. Study of DC &AC Starters
OUTCOMES
Ability to perform speed characteristic of different electrical machine

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CONTENTS
S. No. Name of the experiment Page No
1 Study of DC & AC Starters 04
2 Speed control of DC Shunt motor(Armature, Field control) 12
3 Load test on a DC Shunt motor
15
4 Load test on a DC Series motor 18
5 Open circuit and load characteristics of a DC Shunt Generator 21
6 Load test on a single phase transformer 25
7 Open circuit and short circuit tests on a single phase transformer 28
8 Regulation of a 3 phase alternator by EMF and MMF method 34
9 Load test on single phase Induction Motor 40
10 Load test on a three phase squirrel cage induction motor 44
11 Open circuit and load characteristics of a DC Series Generator 47
12 Speed Control of 3-Phase Slip Ring Induction Motor 53
13 V curves and inverted V curves of synchronous Motor 56

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Ex No: 1 Date:
STUDY OF DC AND AC STARTERS
AIM:
To study the different kinds of D.C motor starters
APPARATUS REQUIRED:
Sl No. Name of the apparatus Quantity
1 Two Point starter 1
2 Three Point starter 1
3 Four Point starter 1
THEORY:
The value of the armature current in a D.C shunt motor is given by
Ia = ( V – Eb )/ Ra
Where V = applied voltage.
Ra = armature resistance.
E b = Back .e.m.f .
In practice the value of the armature resistance is of the order of 1 ohms and at the instant of starting the
value of the back e.m.f is zero volts. Therefore under starting conditions the value of the armature current
is very high. This high inrush current at the time of starting may damage the motor. To protect the motor
from such dangerous current the D.C motors are always started using starters.
The types of D.C motor starters are
i) Two point starters
ii) Three point starters
iii) Four point starters.
The functions of the starters are
i) It protects the motor from dangerous high speed.
ii) It protects the motor from overloads.
i) TWO POINT STARTERS:
It is used for starting D.C. series motors which has the problem of over speeding due to the loss of load
from its shaft. Here for starting the motor the control arm is moved in clock-wise direction from its OFF
position to the ON position against the spring tension. The control arm is held in the ON position by the
electromagnet E. The exciting coil of the hold-on electromagnet E is connected in series with the armature
circuit. If the motor loses its load, current decreases and hence the strength of the electromagnet also
decreases. The control arm returns to the OFF position due to the spring tension, Thus preventing the
motor from over speeding. The starter also returns to the OFF position

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when the supply voltage decreases appreciably. L and F are the two points of the starter which are
connected with the motor terminals.
ii) THREE POINT STARTER: ( refer fig 2 )
It is used for starting the shunt or compound motor. The coil of the hold on electromagnet E is
connected in series with the shunt field coil. In the case of disconnection in the field circuit the control
arm will return to its OFF position due to spring tension. This is necessary because the shunt motor will
over speed if it loses excitation. The starter also returns to the OFF position in case of low voltage supply
or complete failure of the supply. This protection is therefore is called No Volt Release ( NVR).
Over load protection:
When the motor is over loaded it draws a heavy current. This heavy current also flows through the
exciting coil of the over load electromagnet (OLR). The electromagnet then pulls an iron piece upwar6.ds
which short circuits the coils of the NVR coil. The hold on magnet gets de-energized and therefore the
starter arm returns to the OFF position, thus protecting the motor against overload. L, A and F are the
three terminals of the three point starter.
iii) FOUR POINT STARTER:
The connection diagram of the four point starter is shown in fig 3. In a four point starter arm
touches the starting resistance, the current from the supply is divided into three paths. One through the
starting resistance and the armature, one through the field circuit, and one through the NVR coil. A
protective resistance is connected in series with the NVR coil. Since in a four point starter the NVR coil is
independent of the of the field ckt connection, the d.c motor may over speed if there is a break in the field
circuit. A D.C motor can be stopped by opening the main switch. The steps of the starting resistance are so
designed that the armature current will remain within the certain limits and will not change the torque
developed by the motor to a great extent.
STUDY OF AC STARTERS
AUTO –TRANSFORMER STARTING
An auto transformer starter consists of an auto transformer and a switch as shown in the fig. When
the switch S is put on START position, a reduced voltage is applied across the motor terminals. When the
motor picks up speed, say to 80 per cent of its moral speed, the switch is put to RUN position. Then the
auto-transformer is cut out of the circuit and full rated voltage gets applied across the motor terminals.
The circuit dia in the fig is for a manual auto-transformer starter. This can be made push button operated
automatic controlled starter so that the contacts switch over from start to run position as the motor speed
picks up to 80% of its speed. Over-load protection relay has not been shown in the figure. The switch S is
air-break type for small motors and oil break type for large motors. Auto transformer may have more than
one tapping to enable the user select any suitable starting voltage depending upon the conditions.
Series resistors or reactors can be used to cause voltage drop in them and thereby allow low voltage to be
applied across the motor terminals at starting. These are cut out of the circuit as the motor picks up speed.

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STAR- DELTA METHOD OF STARTING:
The startor phase windings are first connected in star and full voltage is connected across its free
terminals. As the motor picks up speed, the windings are disconnected through a switch and they are
reconnected in delta across the supply terminals. The current drawn by the motor from the lines is reduced
to as compared to the current it would have drawn if connected in delta. The motor windings, first in star
and then in delta the line current drawn by the motor at starting is reduced to one third as compared to
starting current with the windings delta-connected.
In making connections for star-delta starting, care should be taken such that sequence of supply
connections to the winding terminals does not change while changing from star connection to delta
connection. Otherwise the motor will start rotating in the opposite direction, when connections are
changed from star to delta. Star-delta starters are available for manual operation using push button control.
An automatic star – delta starter used time delay relays(T.D.R) through which star to delta connections
take place automatically with some pre-fixed time delay. The delay time of the T.D.R is fixed keeping in
view the starting time of the motor.

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FULL VOLTAGE OR DIRECT –ON-LINE STARTING (DOL STARTER)
When full voltage is connected across the stator terminals of an induction motor, large current is
drawn by the windings. This is because, at starting the induction motor behaves as a short circuited
transformer with its secondary, i.e. the rotor separated from the primary, i.e. the stator by a small air-gap.
At starting when the rotor is at standstill, emf is induced in the rotor circuit exactly similar to the
emf induced in the secondary winding of a transformer. This induced emf of the rotor will circulate a very
large current through its windings. The primary will draw very large current from the supply mains to
balance the rotor ampere-turns. To limit the stator and rotor currents at starting to a safe value, it may be
necessary to reduce the stator supply voltage to a low value. If induction motors are started direct-on-line
such a heavy starting current of short duration may not cause harm to the motor since the construction of
induction motors are rugged. Other motors and equipment connected to the supply lines will receive
reduced voltage. In industrial installations, however, if a number of large motors are started by this
method, the voltage drop will be very high and may be really objectionable for the other types of loads
connected to the system. The amount of voltage drop will not only be dependent on the size of the motor
but also on factors like the capacity of the power supply system, the size and length of the line leading to
the motors etc. Indian Electricity Rule restricts direct on line starting of 3 phase induction motors above 5
hp.

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PRIMARY RESISTORS (Or) STATOR RESISTANCE STARTER
Their purpose is to drop some voltage and hence reduce the voltage applied across the motor
terminals. In this way, the initial current drawn by the motor is reduced. However it should be noted that
whereas current varies directly as the voltage, the torque varies as square of applied voltage. If the voltage
applied across the motor terminals is reduced by 50%, starting current is reduced by 50%, but torque is
reduced by 25% of the full voltage value. By using primary resistors the applied voltage/phase can be
reduced by a fraction ‘x’ and it additionally improves the power factor of the line slightly. Th ratio of the
starting torque to full load torque is x2
of that obtained with direct switching or across the line starting.
This method is useful for the smooth starting of small machines only.

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Stator Resistance Starter
ROTOR RESISTANCE STARTER
The slip ring induction motors are always started with full line voltage applied across the stator terminals.
The value of starting current is adjusted by introducing a variable resistance in the rotor circuit. The
controlling resistance is in the form of a rheostat, connected in star, the resistance being gradually cut out
of the rotor circuit, as the motor gathers speed. Increasing the rotor resistance reduces the starting current
at the same time the starting torque is also increased due to improvement in power factor. The controlling
rheostat is either of stud or contactor type and may be hand operated or automatic.
Result:
Thus the dc and ac motor starters were studied.

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Ex No: 2 Date:
SPEED CONTROL OF DC SHUNT MOTOR (ARMATURE, FIELD CONTROL)
AIM
To conduct an experiment to control the speed of the given dc shunt motor by field and armature control
method also to draw its characteristic curves.
APPRATUSREQUIRED
S.NO
NAMEOFTHE
APPARATUS
TYPE RANGE QUANTIT
Y
l
2
3
4
5
Ammeter
Voltmeter
Rheostat
Rheostat
Tachomete
r
MC
MC
Wire
wound
Wire
wound
Digital
(0-2A)
(0-300V)
300Ω/1.7A
50Ω/5A
l
l
l
l
l
PRECAUTION
•The motor field rheostat should be kept at minimum resistance position.
•The motor armature rheostat should be kept at maximum resistance position.
•The motor should be in no load condition throughout the experiment.
PROCEDURE
Field Control Method (Flux Control Method)
1.Connections are given as per the circuit diagram.
2.Using the three point starter the motor is started to run.
3.The armature rheostat is adjusted to run the motor at rated speed by means of
applying the rated voltage.
4.The field rheostat is varied gradually and the corresponding field current and speed
are noted up to l20% of the rated speed by keeping the Armature current as
constant.
5.The motor is switched off using the DPST switch after bringing all the rheostats to
their initial position.

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CIRCUIT DIAGRAM FOR SPEED CONTROL OF DC SHUNT MOTOR
Tabulation for Speed control of DC Shunt motor
S.No.
Armature Control Method Field Control Method
Field Current: Armature Current:
Armature
Voltage(Va)
Speed
(N)
Field
Current
(If)
Speed
(N)
Volts RPM Amps RPM
Armature Control Method (Voltage Control Method)
1.Connections are given as per the circuit diagram.
2.Using the three point starter the motor is started to run.
3.The armature rheostat is adjusted to run the motor at rated speed by means of
applying the rated voltage.

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4.The armature rheostat is varied gradually and the corresponding armature voltage
and speeds are noted up to the rated voltage.
5.The motor is switched off using the DPST switch after bringing all the rheostats to
their initial position
GRAPH
The graph are drawn as
• Field current Vs Speed
• Armature current Vs Speed
RESULT:
Thus the speed control of the given DC shunt motor using field control and armature
Control method and its characteristic curves are drawn.

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Ex No: 3 Date:
LOAD TEST ON DC SHUNT MOTOR
AIM
To conduct the load test on a given dc shunt motor and draw its performance curves.
APPRATUSREQUIRED
S. NO
NAMEOFTHE
APPARATUS
TYPE RANGE QUANTITY
1
2
3
4
Ammeter
Voltmeter
Rheostat
Tachometer
MC
MC
Wire wound
Digital
(0-20A)
(0-300V)
300Ω/1.7A
1
1
1
1
FORMULAE
1. Torque T = (S1~S2) ×(R+t/2)×9.81 in N-m.
Where R- Radius of the Break drum in m
t- Thickness of the Belt in m.
S1,S2-Spring balance reading in Kg.
2. Input power = VL×ILin Watts.
Where VL–Load Voltage in Volts.
IL-Load current in Amps.
3. Output power = 2ΠNT/60 in Watts.
Where N- Speed of the armature in rpm.
T- Torque in N-m.
4. Percentage of Efficiency = (Output power / Input power) ×100
PRECAUTION
1.The motor field rheostat should be kept at minimum resistance position.
2.At the time of starting the motor should be in no load condition.

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CIRCUIT DIAGRAM FOR LOAD TEST ON DC SHUNT MOTOR
Mechanical Characteristics
Electrical Characteristics
in %
T in N-m
Speed in rpm
IL in Amps
N IL T %
Output power in watts
T Vs N
Speed(N)inrpm
Torque ( T ) in N-m

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TABULATION FOR LOAD TEST ON DC SHUNT MOTOR
Radius of the brake drum (R) = in m Thickness of the belt (t) = in m
Sl
No
Load
Voltage
in
Volts
Load
current
I
Amps
speed
in
rpm
Spring balance
Reading
In kg
Input
Power
in
Watts
Torque
in NM
Output
Power
in
Watts
Efficiency
in %
S1 S2 S1 S2
PROCEDURE:
1. Connections are given as per the circuit diagram.
2. Observe the precaution and using three-point starter the motor is started to run at the rated speed by
adjusting the field rheostat if necessary.
3. The meter readings are noted at no load condition.
4. By using break drum with spring balance arrangement the motor is loaded and the corresponding
readings are noted up to the rated current.
5. After observation of all the readings the load is released gradually
6. The motor is switched off by using DPST switch.
GRAPH
The graphs are drawn as
•Output power Vs Efficiency
•Output power Vs Armature current
•Output power Vs Torque
•Output power Vs Speed
•Torque Vs Speed
RESULT
Thus the load test on DC shunt motor was conducted and its performance curves are drawn.

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Ex No: 4 Date:
LOAD TEST ON DC SERIES MOTOR
AIM
To conduct load test on DC series motor and to find efficiency
APPARATUS REQUIRED
S.No Apparatus Range Type Quantity
1 Ammeter (0-20)A MC 1
2 Voltmeter (0-300)V MC 1
3 Digital Tachometer 1
PRECAUTIONS:
1. The motor should be started and stopped with load.
2. Brake drum should be cooled with water when it is under load.
FORMULAE
1. Torque T = (S1~S2) ×(R+t/2)×9.81 in N-m.
Where R- Radius of the Brake drum in m
t- Thickness of the Belt in m.
S1,S2-Spring balance reading in Kg.
2. Input power = VL×IL in Watts.
Where VL–Load Voltage in Volts.
IL-Load current in Amps.
3. Output power = 2ΠNT/60 in Watts.
Where N- Speed of the armature in rpm.
T- Torque in N-m.
4. Percentage of Efficiency = (Output power / Input power) ×100
PROCEDURE:
2. Observe the precaution and using two-point starter the motor is started
3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings are noted.
4. After bringing the load to initial position, DPST switch is opened.

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Circuit Diagram of Load test on DC Series Motor
Model Graph

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TABULATION FOR LOAD TEST ON DC SERIES MOTOR
Radius of the brake drum (R) = in m Thickness of the belt (t) = in m
Sl
No
Load
Voltage
in
Volts
Load
current
I
Amps
speed
in
rpm
Spring balance
Reading
In kg
Input
Power
in
Watts
Torque
in NM
Output
Power
in
Watts
Efficiency
in %
S1 S2 S1 S2
GRAPH
The graphs are drawn as
•Output power Vs Efficiency
•Output power Vs Torque
•Output power Vs Speed
RESULT
Thus the load test on DC series motor was conducted and its performance curves are drawn.

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Ex No: 5 Date:
OPEN CIRCUIT AND LOAD CHARACTERISTICS OF DC SHUNT GENERATOR
AIM
To conduct the open circuit test and the load test on a given self excited dc shunt generator and draw the
characteristic curves.
APPRATUS REQUIRED
S.No Name of the Apparatus Range Type Quantity
3 Voltmeter (0-300)V MC 1
4 Rheostat 300Ω/1.5A Wire Wound 1
5 Rheostat 700Ω/1.8A Wire Wound 1
6 Digital Tachometer 1
7 Resistive Load Variable 1
8 DPST Switch 1
9 SPST Switch 1
PRECAUTION
• The motor field rheostat should be kept at minimum resistance position.
• The generator field rheostat should be kept at maximum resistance position.
• At the time of starting, the generator should be in no load condition.
PROCEDURE
Open circuit test
• Connections are given as per the circuit diagram.
• The Prime Mover is started with the help of the three point starter and it is made to
run at rated speed when the Generator is disconnected from the load by DPST
switch.
• By varying the Generator field rheostat gradually, the Open Circuit Voltage (Eo)
and corresponding Field Current (If) are tabulated up to 150 % of Rated Voltage of
Generator.
• The motor is switched off by using the DPST switch after bringing all the rheostats
to their initial position.
Load test
• Connections are given as per the circuit diagram.
• The Prime Mover is started with the help of the three point starter and it is made to
run at rated speed when the Generator is disconnected from the load by DPST
switch.
• By varying the Generator field rheostat gradually, the Rated Voltage (Eg) is obtained.
• The Ammeter and Voltmeter readings are observed at no load condition.
• The Ammeter and Voltmeter readings are observed for different loads up to the
rated current by closing the DPST switch.
• After tabulating all the readings the load is brought to its initial position gradually.
• The Prime Mover is switched off using the DPST switch after bringing all the
rheostats to their initial position.

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CIRCUIT DIAGRAM FOR OPEN CIRCUIT AND LOAD TEST ON SELF EXCITED DC SHUNT
GENERATOR
MEASUREMENT OF ARMATURE RESISTANCE (Ra)

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Model graph
Internal (EgVsIa) and External (VL Vs IL)
Characteristics
Open circuit characteristics
GRAPH
• Open Circuit Voltage Vs Field Current
• Load Voltage Vs Load Current
Tabulation for Open Circuit Test on Self Excited D.C Shunt Generator:
Sl.no Open circuit
voltage in
Volts [Eo]
Field current
in Amps [If]
If
Field current
[If] in amps
Opencircuitvoltagein
Volts[Eo]
EoVs If
Load current [IL] in amps
Armature current [Ia] in amps
LoadvoltageinVolts[VL]
GeneratedemfinVolts[Eg]
EgVsIa
VL Vs IL

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Tabulation for Load Test:
Sl.no
Armature
current
[Ia] in
Amps
Load
voltage
[VL] in
Volts
Load
current
[IL] in
Amps
Armature
drop Ia Ra
In volts
Generated
emf [Eg =
VL+IaRa]
In volts
RESULT:
Thus the open circuit test and load test on a given self excited DC generator was conducted and the
characteristic curves were drawn.

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Ex No: 6 Date:
LOAD TEST ON SINGLE PHASE TRANSFORMER
AIM
To conduct the load test on a given single phase transformer and draw its performance curves.
APPARATUS REQUIRED
S.NO NAME OF THE
APPARATUS
TYPE RANGE QUANTITY
l
2
3
4
5
6
7
Ammeter
Ammeter
Voltmeter
Voltmeter
Watt meter
Auto Transformer
DPST Switch
MI
MI
MI
MI
UPF
lφ
(0-5A)
(0-20A)
(0-l50V)
(0-300V)
300V/ 5A
23OV/(0-270)V
l
l
l
l
l
l
1
FORMULAE USED
l. Input Power=Wattmeter reading × Multiplication factor in Watts
where Multiplication factor = (Rating of pressure coil × Rating of current coil ×pf)
Full scale reading
2. Output power = VSY × ISY × cosφ in watts
Where VSY – Secondary Voltage in volts
ISY – Secondary current in Amps
3. Percentage of Efficiency = Output Power ×100%
Input Power
4. Percentage Regulation = V0 – VL ×100%
VL
Where VO–No Load Voltage in Volts
VL – Load Voltage in Volts

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CIRCUIT DIAGRAM FOR LOAD TEST ON SINGLE PHASE TRANSFORMER
Tabulation For Load Test on Single Phase Transformer
S.No Primary
Voltage
(VPY)
Volts
Primary
Current
(IPY)
Amps
Secondary
Voltage
(VSY)
Volts
Secondary
Current
(ISY)
Amps
Wattmeter
readings
watts
Input
Power
(W)
Watts
Output
Power
VSYISY
Cosφ
Watts
%
Efficiency
%
Regulation
Obs Act
PROCEDURE
2. The SPST Switch on the Primary side is closed and the DPST Switch on the

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Secondary
Side is opened.
3. The Autotransformer is adjusted to Energize the transformer with rated Primary
Voltage
4. The Volt meters and Ammeters Readings are noted and tabulated at No load condition
5. The DPST switch on the secondary side is closed.
6. The transformer is loaded up to l3O%ofthe Rated Load and corresponding Ammeters,
Voltmeters and Wattmeter readings are noted tabulated.
7. After the observation of all the readings the load is released gradually to its initial
position.
8. The Autotransformer is brought to its initial position
9. The Supply is switched off.
GRAPH
The graph drawn as
• Output power Vs Efficiency
• Output power Vs Regulation
MODEL GRAPH
RESULT
Thus the load test on a given single phase transformer is done and the characteristic curves are
drawn.

28
Ex No: 7 Date:
OPEN CIRCUIT AND SHORT CIRCUIT TEST ON SINGLE PHASE TRANSFORMER
TO DRAW ITS EQUIVALENT CIRCUIT
AIM
To Predetermine the Efficiency and Regulation on a given single phase transformer by
conducting the Open Circuit test and Short Circuit test and also draw its Equivalent circuit.
APPARATUSREQUIRED
S.No Name of the Apparatus Type Range Quantity
l
2
3
4
5
6
Ammeter
Ammeter
Voltmeter
Watt meter
Watt meter
Auto Transformer
MI
MI
MI
LPF
UPF
lφ
(0-lA)
(0-l0A)
(0-150V)
150V/ 2.5A
150V/ 10A
230V/(0-270V)
l
l
2
l
l
l
Formulae Used:
Open circuit test:
1. No load power factor
ococ
oc
IV
W
)(cos 0
WOC = open circuit power in watts
VOC = open circuit voltage in volts
IOC = open circuit current in amps
2. No load working component resistance (RO);
oOC
OC
O
CosI
V
R in ohms
3. No load magnetizing component (XO);
oOC
OC
O
SinI
V
X in ohms
Short circuit test:
4. Equivalent impedance referred to HV side (Z02);
SC
SC
O
I
V
Z 2 in ohms.
5. Equivalent resistance referred to HV side (R02); 22
SC
SC
O
I
W
R in ohms
6. Equivalent reactance referred to HV side (X02);
2
2
2
22 OOO RZX in ohms

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7. Transformation ratio (K);
1
2
V
V
K
8. Equivalent resistance referred to LV side (R01); 2
2
1
K
R
R O
O in ohms
9. Equivalent reactance referred to LV side (X01); 2
2
1
K
X
X O
O in ohms
Efficiency and regulation
10. Output power = )( CosKVAX in watts
11. Copper loss = )( 2
SCWX in watts
12. Total loss WT= )( lossIronlossCu in watts
13. Efficiency = 100
lossTotalpowerOutput
powerOutput
in %
14. Regulation = 100
[
2
22
O
OOSC
V
SinXCosRIX
in %
Where1 V2o–Open Circuit Voltage on HV side.
Precautions:
Auto transformer should be kept at zero volt position.
At the time of starting the experiment DPST switch kept open and transformer should be
no load.
High voltage and low voltage sides of the transformer should be properly used as primary
or secondary respective to experiments.
Procedure (for Open circuit Test)
2. Ensuring the precautions the supply is switched on by closing DPST switch.
3. Auto transformer is adjusted to energize the transformer with primary voltage on LV
side.
4. Voltmeter, ammeter and wattmeter readings are noted at no load condition.
5. Auto transformer is gradually decreased to its initial position.
6. Switch off the supply by DPST.
Procedure (for Short CKT Test)
2. Ensuring the precautions the supply is switched on by closing DPST switch.
3. Auto transformer is adjusted to energize the transformer with primary current on the
HV side.
4. Voltmeter, ammeter and wattmeter readings are noted at no load condition.
5. Auto transformer is gradually decreased to its initial position.
6. Switch off the supply by DPST.

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CIRCUIT DIAGRAM FOR OPEN CIRCUIT TEST ON SINGLE PHASE TRANSFORMER
CIRCUIT DIAGRAM FOR SHORT CIRCUIT TEST ON SINGLE PHASE TRANSFORMER

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Tabulation for OC Test multiplication factor:
Sl.
no
Open circuit
primary current
(IOC) In Amps
Open circuit primary
voltage (VOC) in
Volts
Open circuit power (Woc) in
Watts
Observed Actual
Tabulation for SC Test multiplication factor:
Sl.
No
Short circuit
primary current
(ISC)In Amps
Short circuit primary
voltage (VSC) in Volts
Short circuit power (Wsc) in Watts
Observed Actual
Predetermination of efficiency:
Core (or) Iron loss (Wi) = Watts, KVA rating of Transformer = .
Rated Short circuit current = Amps Short Circuit power (WSC) = .
Fraction
of load/
Load
factor (X)
Short
circuit
current
(ISC X)
in Amps
Output
power )( CosKVAX in
watts
Copper
loss
)( 2
SCWX
in watts
Total loss
SCiT WWW
in watts
Efficiency
TWpo
po
/
/
X 100
in %0.2 0.4 0.6 0.8 1

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Tabulation to predetermine % Voltage regulation:
ISC = RO2= XO2= V2O=
Fractio
n of
load
(X)
Value of Cos Value of Sin
% of Regulation
100
[
2
22
O
OOSC
V
SinXCosRIX
1
0.
8
0.
6
0.
4
0.
2
1
0.
8
0.
6
0.4 0.2 1
0.8 0.6 0.4 0.2
Lag LeadLag LeadLag LeadLag Lead
EQUIVALENT CIRCUIT OF SINGLE PHASE TRANSFORMER REFERRED TO PRIMARY

33
Model Graph
RESULT
Thus the efficiency and regulation of a given single phase transformer by conducting the
open circuit test and short circuit test is determined and the equivalent circuit is drawn.

34
Ex No: 8 Date:
REGULATION OF THREE PHASE ALTERNATOR BY EMF METHOD AND MMF
METHOD
AIM
To pre determine the regulation of a given three phase Alternator by EMF and MMF
method.
APPARATUSREQUIRED
S.No. Name of The Apparatus Type Range Quantity
l.
2.
3.
4.
5.
6.
7.
8.
9.
Ammeter
Ammeter
Ammeter
Voltmeter
Voltmeter
Rheostat
Rheostat
Tachometer
Resistive Load
MC
MC
MI
MI
MC
Wire wound
Wire wound
-
Variable
(0-2A)
(0-10A)
(0-5A)
(0-600V)
(0-50V)
700Ω/0.8A
300Ω/l.5A
-
l
l
lll
1
l
l
1
FORMULAE USED
EMF Method
l. Armature Resistance Ra=l.6Rdcinohms.
Here R dc is the resistance in DC supply.
2. Synchronous impedance
Zs=
Open circuit
voltage(El(ph)) Short
circuit current(Isc)
(from the graph)
3. Synchronous impedance Xs = (Zs2
–Ra2
)in ohms.
4. Open circuit voltage Eo = (Vcosφ+IscRa)2
+(Vsinφ-IscXs)2
inVolts.
(For lagging power
factor)
5. Open circuit voltage Eo = (Vcosφ+IscRa)2
+(Vsinφ-IscXs)2
inVolts
(For leading power factor)
7.Open circuit voltage Eo = (V +IscRa)2
+(IscXs)2
inVolts
(For Unity power factor)
6. Percentage regulation =
Eo–Vrated
VratedX l00(both for EMF & MMF method)

35
MMF Method:
From O.C.C and S.C.C. curves IF1, IF2 are noted. From the IF1, IF2,IFT is calculated from the
formula
IFT = IF1
2
+ IF2
2
+ 2IF1IF2 Cos(180-(90+φ)) for lagging power factor
IFT = IF1
2
+ IF2
2
+ 2IF1IF2 Cos(180-(90-φ)) for leading power factor
For corresponding field currents of IFT find the corresponding open circuits voltage from o.c.c
curve and is tabulated. Using the formula, regulation is found and tabulated.
Where IF1 = Field current required to generate rated terminal voltage,
IF2 = Field current required to circulate full load current at short circuit conditions
IFT = Total field current required for open circuit voltage
PRECAUTION
• The motor field rheostat should be kept in the minimum resistance position.
• The Alternator field Potential divider should be in the maximum voltage
position.
• Initially all Switches are in open position.
PROCEDURE FOR BOTH EMF AND MMF METHOD
1. Connections are made as per the circuit diagram.
2. Give the supply by closing the DPST Switch.
3. UsingtheThreePointstarter1startthemotortorunatthesynchronous
Speed by varying the motor field rheostat.
4 . Conduct an Open Circuit Test by varying the Potential Divider for various
Values of Field Current and tabulate the corresponding Open Circuit Voltage
readings.
5. Conduct a Short Circuit Test by closing the TPST switch and adjust the
Potential divider to set the rated Armature Current and tabulate the
Corresponding Field Current.
6. Conduct a Stator Resistance Test by giving connection as per the circuit
diagram and tabulate the Voltage and Current readings for various resistive
loads.

36
CIRCUIT DIAGRAM FOR REGULATION OF ALTERNATOR BY EMF & MMF
METHOD
MEASUREMENT OF ARMATURE RESISTANCE

37
ShortCircuitCurrent(ISC)inAmps
OpenCircuitVoltage(V0(Ph))inVolts

38
TABULATION FOR REGULATION OF THREE PHASE ALTERNATOR BY EMF AND
MMF METHOD
S.No.
Percentage of
RegulationPower
Factor
EMF Method MMF
MethodLagging Leading Unity Lagging Leading Unity
l. 0.2 - -
2. 0.4 - -
3. 0.6 - -
4. 0.8 - -
5. l.0
TABULATION
Open circuit test:
S.NO Field current(If) Open circuit line
voltage (VOL)
Open circuit phase
voltage (Vo(ph))
Amps Volts Volts

39
Short circuit test:
Tabulation to find out the armature resistance (Ra):
RESULT
Thus the regulation of three phase alternator by EMF and MMF methods and the
regulation curves are drawn.
S.No
Field current(If)
Short Circuit Current
(120 to 150 % of rated
current ) (Isc)
Amps Amps
S.No
Armature
current
(I)
Armature voltage
(V)
Armature Resistance
Ra=V/I
Amps Volts Ohms

40
Ex No: 9 Date:
LOAD TEST ON SINGLE PHASE SQUIRREL CAGE INDUCTION MOTOR
AIM
To conduct a load test on single phase induction motor and to draw the performance
characteristics.
APPARATUS REQUIRED
S.No Name of the Apparatus Type Range Quantity
1 Ammeter MI (0-10)A 1
2 Voltmeter MI (0-300)V 1
3 Wattmeter UPF 300V/10A 1
4 Tachometer 1
FORMULAE USED
1. Torque = (S1-S2) (R+t/2) x 9.81 N-m
Where, S1, S2 – spring balance readings in Kg.
R - Radius of brake drum in m.
t- Thickness of belt in m.
2. Output Power = 2 πNT/60 watts.
N- Rotor speed in rpm.
T- Torque in N-m.
3. Percentage of Efficiency = (Output Power/ Input Power) x 100%.
PRECAUTION
1. The motor should be started without any load.
PROCEDURE:
2. The motor is started by closing the DPST switch.
3. At no load the speed, current, voltage and power are noted down.
4. By applying the load for various values (upto 125% of rated current) of current the above-
mentioned readings are noted.
5. The load is later released and the motor is switched off and the graph is drawn.

41
CIRCUIT DIAGRAM FOR LOAD TEST ON 1φ INDUCTION MOTOR

42
TABULATION FOR LOAD TEST ON 1φ INDUCTION MOTOR
MODEL CALCULATION:
S.No Load
Voltage
in volts
Load
Current
in
Amps
Input
Power in
Watts
Speed
of the
Motor
N rpm
Spring Balance
reading
Torque
T NM
Output
Power
In watts
% Efficiency
S1 S2 (S1-S2)

43
MODEL GRAPH
GRAPH
•Output Power Vs Speed
•Output Power Vs current
•Output Power Vs Torque
•Output Power Vs % Efficiency and
Speed Vs Torque
RESULT
Thus the load test on a given single phase induction motor was done and the characteristic
curves are drawn.

44
Ex No: 10 Date:
LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR
AIM
To conduct a load test on a three phase squirrel cage induction motor and to draw the
performance characteristic curves.
APPARATUS REQUIRED
FORMULAE USED
1. Torque = (S1-S2) (R+t/2) x 9.81 N-m
Where, S1, S2 – spring balance readings in Kg.
R - Radius of brake drum in m.
t- Thickness of belt in m.
2. Output Power = 2 πNT/60 watts.
N- Rotor speed in rpm.
T- Torque in N-m.
3. Input Power = (W1+W2) Watts.
W1, W2 – Wattmeter readings in Watts.
4. Percentage of Efficiency = (Output Power/ Input Power) x 100%.
5. Power factor = (W1+W2)/√3 VL IL.
PRECAUTION
1. The motor should be started without any load.

45
CIRCUIT DIAGRAM FOR LOAD TEST ON THREE PHASE INDUCTION MOTOR
PROCEDURE:
2. The TPSTS is closed and the motor is started using star delta starter to run at rated speed.
3. At no load the speed, current, voltage and power are noted down.
4. By applying the load for various values of current the above-mentioned readings are noted.
5. The load is later released and the motor is switched off and the graph is drawn.
GRAPH
•Output Power Vs Speed
•Output Power Vs Line current
•Output Power Vs Torque
•Output Power Vs Power factor
•Output Power Vs % Efficiency

46
Tabulation for Load test on three phase Induction Motor
S.
No
Load
Voltage
in volts
Load
Curre
nt in
Amps
Wattmeter
Reading in
Watts
Input
Power in
Watts
Speed
N
rpm
Spring
Balance
Reading in kg
Torque
T
NM
Output
Power
(Watts)
%
Effici
ency
Power
Factor
cosφ
W1 W2 (W1+W2) S1 S2 (S1-
S2)
Model Graph
Electrical Characteristics Mechanical Characteristics
RESULT
Thus the load test on a given three phase squirrel cage induction motor was done and the
characteristic curves are drawn.

47
Ex No: 11 Date:
OPEN CIRCUIT AND LOAD CHARACTERISTICS OF
DC SERIES GENERATOR
AIM:
To obtain open circuit characteristics and load characteristics of a DC series generator and
find its critical resistance
APPARATUS REQUIRED:
Sl. No. Apparatus Range & Type Quantity
1 DC Series Generator Set up 1 No
2 Voltmeter (0-300 V), MC 1 No
3 Ammeter
(0-2 A), MC
1 each
(0-20) A MC
4 Rheostats
300 Ω/ 1.5 A
1 each
700 Ω1.8 A
5 SPST & DPST switch - 1 No
6 Digital Tachometer - 1 No
7 Connecting wires - As Required
THEORY
In a D.C. series generator the field winding is connected in series with the armature
winding. In this case the armature current flows through the field winding as well as the load. Since
the armature winding and the field winding are in series the armature current is the same as the
field current. The field winding has less number of turns of thick wire and hence its resistance is
low.
Ia = Ise = IL
The load characteristics of a D.C. series generator are plotted with the load current (IL) on
the X-axis and the Voltage (V) on the Y-axis. As in the case of the D.C. shunt generator there are
two types of load characteristics:
1. Internal characteristics – Induced emf E vs Load current IL. Here the drop is due to
armature reaction.
2. External characteristics – Terminal Voltage V vs Load current IL. Here the drop is due
to armature and series field resistance.
The Voltage equation of a D.C. series generator is given
by V = E – Ia (Ra + Rse)
The load characteristics are shown in the model graph. It will be noticed that a series
generator has rising voltage characteristic i.e. with increase in load, its voltage is also increased, but

48
it is seen that at high loads, the voltage starts decreasing due to excessive demagnetizing effects of
armature reaction. In fact, terminal voltage starts decreasing as load current is increased as shown
by the dotted curve and for a particular high value of load current the terminal voltage is reduced to
zero.
FORMULA:
Eg = V + Ia (Ra+Rse) (V)
Ia = IL = If (A) [Series generator]
where
Eg : Generated EMF in V
V : Terminal Voltage in V
Ia : Armature Current in A
IL : Line Current in A
If : Field Current in A
Ra : Armature Resistance in Ohm
CIRCUIT DIAGRAM-OPEN CIRCUIT AND LOAD CHARACTERISTICS OF DC SERIES
GENERATOR

49
OPEN CIRCUIT TEST
PRECAUTIONS:
1. The field rheostat of motor should be in minimum resistance position.
2. The field rheostat of generator should be in maximum resistance position.
3. No load should be connected to generator.
4. Generator field should be separately excited.
PROCEDURE:
2. After checking minimum position of motor field rheostat, maximum position of generator
field rheostat, DPST switch is closed and starting resistance is gradually removed.
3. By adjusting the motor field rheostat, the motor is brought to rated speed.
4. By varying the generator field rheostat, voltmeter and ammeter readings are taken.

50
5. After bringing the generator rheostat to maximum position, field rheostat of motor to
minimum position, DPST switch is opened.
LOAD TEST
PRECAUTIONS:
1. The field rheostat of motor should be at minimum position.
2. No load should be connected to generator at the time of starting and stopping.
PROCEDURE:
1. Connections are given as shown in the circuit diagram.
2. The DC supply is switched ON and the DC shunt motor (prime mover) is started using the 3-
point starter. The motor is brought to its rated speed by adjusting its field rheostat and the
same is checked with the help of a tachometer.
3. The load DPST is now closed and the loading rheostat is switched on in steps and at each step
the motor speed is maintained constant by adjusting the motor field rheostat and then the
terminal voltage (VL) and the load current (IL) are noted down.
4. The procedure is continued until the load current is equal to 120% of the rated current of the
generator. After the experiment is completed the load on the generator is gradually decreased
to minimum, bring motor field rheostat to minimum position and then the supply is switched
OFF.
5. The resistances of the armature and the series field winding of the generator are found by
giving low voltage supply and connecting a voltmeter and ammeter.
6. The external and internal characteristics of the given DC series generator are plotted.
TABULATION
Armature Resistance - Ra:
_______Ω
OPEN CIRCUIT TEST
S. No.
Field Current Armature Voltage
If (A) Eo (V)
1
2
3
4
5

51
LOAD TEST
S. No.
Load Current Terminal Voltage Ia *(Ra+Rse) Eg =Vt + Ia (Ra+Rse)
IL= Ia = If (A) Vt (V) (V) (V)
1
2
3
4
5
6
MODEL CALCULATION

52
MODEL GRAPH
OC TEST & LOAD TEST
RESULT:
Thus the open circuit test and load test on a given DC Series generator was conducted and the
characteristic curves were drawn.

53
Ex No: 12 Date:
SPEED CONTROL OF 3-PHASE SLIP RING INDCTION MOTOR
AIM:
To control the speed of three phase slip ring induction motor and draw its performance
characteristics.
APPARATUS REQUIRED:
Sl. No. Apparatus Range & Type Quantity
1 3 Phase Slip Ring Induction motor 1 No
2 Ammeter (0-2)A MI 1 No
3 Voltmeter (0-75)V MI
1 each
4 External resistance 1 each
270Ω/5Amps
5 Digital Tachometer 1 No
6 Connecting wires - As Required
7 TPST Switch 1
FORMULA USED:
(i)Rr=Vrp/Ir (Ω)
(ii) Vrp=Vr/√3 (Volt)
THEORY:
Rotor Rheostat Control:
In this method, which is applicable to slip ring induction motors alone, the motor speed is
reduced by introducing an external resistance in the rotor circuit. For this purpose, the rotor
starter may be used provided it is continuously rated. This method is in fact similar to the
armature rheostat control method of d.c shunt motors.
PROCEDURE :
1. The connections are given as per the circuit diagram.
2. The A.C supply is given to the motor by closing the TPST switch.
3. Initially resistance of the rotor resistance starter is kept at maximum resistance position.
4. Now gradually reduce the resistance of the rotor resistance starter and note
down the corresponding meter readings.

54
CIRCUIT DIAGRAM FOR SPEED CONTROL OF 3-PHASE SLIP RING INDCTION
MOTOR

55
TABULATION:
S.NO Rotor Voltage(Vr) Vrp Rotor Current
(Ir)
Speed (rpm) Rotor Resistance(ohm)
MODELCALCULATION:
GRAPH:
Draw a graph of rotor external resistance versus speed
RESULT:
Thus the speed of 3 phase slip ring induction motor was controlled by rotor resistance control method.

56
Ex No: 13 Date:
V AND INVERTED V CURVES OF THREE PHASE
SYNCHRONOUS MOTOR
AIM:
To draw V and inverted V curves for given three phase synchronous motor.
APPARATUS REQUIRED:
S. No. Name of the Apparatus Range Type Quantity
1 Voltmeter (0 – 600 V) M. I. 1
2 Ammeter (0 – 10 A) M. I. 1
3 Ammeter (0 – 2 A) M. C. 1
4 Wattmeter
600 V, 10 A
Double element UPF 1
5 Tachometer Digital 1
6
Three phase Auto
(0 – 470 V) - 1
Transformer

57
CIRCUIT DIAGRAM: V AND INVERTED V CURVES OF THREE PHASE
SYNCHRONOUS MOTOR
PRECAUTION
1. All the switches should be kept open at the time of starting the experiment.
2. The potential divider in the field circuit of synchronous motor should be kept at
minimum potential position.
PROCEDURE
2. Close the T. P. S. T. switch.
3. The auto transformer is varied gradually to start the motor.
4. The auto transformer is adjusted till the voltmeter reads the rated voltage of the
synchronous motor.
5. Close the D. P. S. T. switch and increase the field current.
6. At no load condition, increase the field current in steps and note down the
corresponding armature current.
7. The potential divider is brought to the minimum potential position.
8. Repeat the same procedure for different load conditions.
9. Reduce the load on the motor.

58
10. Reduce the field current to zero value.
11. Reduce voltage by varying auto transformer.
12. Open all the switches.

59
GRAPH
Field current, If Vs Armature current, Ia
Field current, If Vs Power factor, cosф
RESULT
Thus the V and inverted V curves of the given synchronous motor have been drawn.

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