FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
E
FRANCIS XAVIER ENGINEERING COLLEGE
TIRUNELVELI
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
EE 6365 ELECTRICAL ENGINEERING
LABORATORY
MANUAL
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
LIST OF EXPERIMENTS
1. Load test on DC Shunt & DC Series motor
2. O.C.C & Load characteristics of DC Shunt and DC AC generator
E
3. Speed control of DC shunt motor
LL
CO
5. O.C & S.C Test on a single phase transformer
EG
4. Load test on single phase transformer
6. Regulation of an alternator by EMF & MMF methods.
TGG
7. V curves and Inverted V curves of Synchronous Motor
RIER
AFE
N
8. Load test on three phase squirrel cage Induction motor
9. Speed control of three phase Slip ring Induction Motor
AD
V
10.Load test on single phase Induction Motor.
FR
A
N
CI
S
X
11.Study of DC & AC Starters
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM OF DC SERIES MOTOR
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 1a
LOAD TEST ON DC SERIES MOTOR
Date:
Aim:
To perform load test on the given D.C series motor and to obtain the performance
characteristics.
Apparatus Required:
Name of the apparatus
Range
Type
Quantity
EG
E
S.No
Voltmeter
MC
2
Ammeter
MC
3
Rheostat
Wire wound
4
Tachometer
5
Connecting wires
CO
LL
1
RIER
AFE
N
TGG
Analog
Formulae:
X
AD
V
Input Power  VxI Watts
S
Torque  {9.81( S1 xS 2 ) R}Nm
A
N
CI
R  radius of brake drum
FR
Output Power 
% Efficiency 
2NT
Watts
60
output power
X 100
input power
Precautions:
1. The motor should be started with some load.
2. Brake drum should be cooled throughout the experiment.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabular Column:
I
(Amps)
N
(rpm)
S1
(Kg)
S2
(Kg)
S1~S2
(Kg)
T
(Nm)
Input
(Watts)
Output
(Watts)
RIER
AFE
N
TGG
CO
LL
EG
E
V
(Volts)
T
%
CI
IL
A
N
N
S
X
AD
V
Model Graph:
 in %
T in N-m
Speed in rpm
IL in Amps
FR
S.No
Output power in watts
Procedure:
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Efficiency
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
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.
E
6. At a minimum safe load the DPST switch is opened.
LL
EG
7. Disconnect and return the apparatus.
CO
Result:
The load test on the given D.C series motor was conducted and its performance
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
characteristics were drawn.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM FOR LOAD TEST ON DC SHUNT MOTOR
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 1 b
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
Range
Type
Quantity
Voltmeter
MC
2
Ammeter
MC
3
Rheostat
Wire wound
4
Connecting wires
5
Tachometer
CO
LL
EG
E
1
TGG
Digital
RIER
AFE
N
Formulae:
Input Power  VxI Watts
AD
V
Torque  {9.81( S1 xS 2 ) R}Nm
X
R  radius of brake drum
2NT
Watts
60
A
N
CI
S
Output Power 
FR
% Efficiency 
output power
X 100
input power
Precautions:
1. The motor field rheostat should be kept at minimum resistance position.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabular Column:
I
(Amps)
N
(rpm)
S1
(Kg)
S2
(Kg)
S1~S2
(Kg)
T
(Nm)
Input
(Watts)
Output
(Watts)
RIER
AFE
N
TGG
CO
LL
EG
E
V
(Volts)
IL
T
%
A
N
N
CI
S
X
AD
V
Model Graph:
FR
S.No
 in %
T in N-m
Speed in rpm
IL in Amps
Output power in watts
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Efficiency
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Procedure:
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. 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
TGG
CO
7. Disconnect and return the apparatus.
EG
6. At a minimum safe load the DPST switch is opened.
LL
reaching dangerously high values while reducing the load.
E
various line currents as the load is applied. Care must be taken to avoid the speed
N
Result:
FR
A
N
CI
S
X
AD
V
characteristics were drawn.
RIER
AFE
The load test on the given D.C shunt motor was conducted and its performance
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM FOR OPEN CIRCUIT AND LOAD TEST ON D.C
SEPARATELY EXCITED SHUNT GENERATOR
FR
A
N
CI
S
CIRCUIT DIAGRAM TO FIND ARMATURE RESISTENCE
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex.No:2 OPEN CIRCUIT AND LOAD CHARACTERISTICS OF SEPARATELY
EXCITIED DC SHUNT GENERATOR
Date:
Aim:
To draw open circuit characteristics and load characteristics of the given separately
excited DC shunt generator.
Apparatus required:
Name
Range
Type
Quantity
E
Sl no.
Voltmeter
MC
2
Ammeter
MC
3
Rheostat
Wire wound
4
Tachometer
5
Connecting wires
CO
LL
EG
1
RIER
AFE
N
TGG
Analog
AD
V
Precaution:
1. The field rheostat on the motor side must be kept at minimum resistance position
X
at the time of starting.
CI
S
2. The field potentiometer on the generator side must be kept at maximum potential
A
N
position at the time of starting.
3. DPST switches must be kept open at the time of power on.
FR
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.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabular column:
Speed = _________rpm
If (amps)
Eo (volts)
CO
LL
EG
E
S. No.
N
Field
current If
in amps
Armature
current
[Ia] in
Amps
(Ia=If+IL)
Armature
drop=
Ia* Ra in
volts
Generated emf
[Eg = VL+IaRa]
in
volts
X
AD
V
Sl.no
Load
voltage
[VL] in
Volts
RIER
AFE
Load
current
[IL] in
Amps
TGG
Load Test:
Armature voltage
Va in volts
Armature current
Ia in amps
Ra = Va/ Ia in ohms
FR
A
N
Sl.no
CI
S
To find Armature Resistance:
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
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
E
rated voltage. The speed is maintained constant throughout this process.
EG
9. The generator terminal voltage is minimized to zero.
LL
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
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
bring it back to start position)
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
MODEL GRAPH:
LL
EG
E
Eo
CO
If
X
AD
V
VL Vs IL
RIER
AFE
Eg Vs Ia
N
TGG
Load voltage in Volts [VL]
Generated emf in Volts [Eg]
Internal (Eg Vs Ia) and External (VL Vs IL) characteristics
FR
A
N
CI
S
Load current [IL] in amps
Armature current [Ia] in amps
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FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Result
Thus the open circuit characteristics and load characteristics of a
separately excited DC shunt generator are drawn.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Model Graph
Field control method
X
AD
V
Armature Control method
RIER
AFE
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM OF SPEED CONTROL OF DC SHUNT MOTOR
Speed
rpm
FR
A
N
CI
S
Speed
rpm
Armature voltage (volts)
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Field current(amps)
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex.No:3
Date:
SPEED CONTROL OF DC SHUNT MOTOR
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)
Range
Type
Quantity
LL
Name of the apparatus
Ammeter
M.C
2.
Volt meter
3.
Tacho meter
4.
Rheostat
5.
Connecting wires
CO
1.
TGG
M.C
Analog
N
Wire wound
RIER
AFE
Sl.no
EG
E
Apparatus Required:
Precautions:
AD
V
1. The field rheostat must be kept at minimum resistance position at
X
the time of starting
CI
the time of starting
S
2. The armature rheostat must be kept at maximum resistance position at
A
N
Procedure:
(i).Armature control method:
FR
1. Make the connections as per the circuit diagram
2. Switch on the supply
3. Keep the field current constant and for different armature voltage (by varying
armature rheostat) note down the corresponding speed.
4. Bring back the rheostat to initial position and switch off the supply
(ii) Field control method
1. Switch on the supply
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabular Column
(i).Armature control method:
Field current (If ) =
Armature voltage
(volts)
Speed
(rpm)
(ii) Field control method
AD
V
Armature voltage (Va ) =
RIER
AFE
N
TGG
CO
LL
EG
E
SL.No
Field current
(amps)
FR
A
N
CI
S
X
SL.No
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Speed
(rpm)
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
2. Start the motor by closing the DPST switch
3. Keep the armature voltage constant and for various field current note down the
corresponding speed.
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
4. Bring back the rheostat to initial position and switch off the supply
Result:
Thus the speed control of the DC shunt motor was conducted.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM OF LOAD TEST ON A SINGLE PHASE TRANSFORMER
FR
A
N
CI
S
X
AD
V
RIER
AFE
Model Graph:
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 4
LOAD TEST ON SINGLE PHASE TRANSFORMER
Date:
Aim:
To perform load test on a single phase transformer and determine its performance
characteristics
Apparatus Required:
Name of the apparatus
Range
Type
Quantity
EG
E
Sl.no
Ammeter
M.I
2.
Volt meter
MI.
3.
Watt meter
Dynamo meter
4.
Connecting wires
RIER
AFE
N
TGG
CO
LL
1.
Formulae:
watts
AD
V
Input power = W1 x M.F1
Output power = W2 x M.F2 watts
X
Output power
S
Efficiency =
X 100 %
A
N
CI
Input power
E 02 - V 2
FR
Regulation =
X 100 %
E 02
E 02 - No load secondary voltage
V2
- Secondary voltage at various loads
M.F – Multiplication factor
W1, W2 - Wattmeter readings
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabular Column:
Input
VL.V
IL.V
WL.V
(W)
VH.V
(V)
IH.V
(A)
WH.V
 (%)
(watts)
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
Sl.
No
Out put
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%V reg
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
V I cos 
Multiplication factor (M.F) =
No of divisions in the watt meter
Precautions:
1. Auto transformer must be kept at minimum potential point
2. There should be no load at the time of starting the experiment
Procedure:
EG
E
1. Make the connections as per the circuit diagram
2. Switch on the supply and vary the autotransformer to get rated primary voltage
LL
3. Note down the no load readings
CO
4. Add the load in steps and note down all the meter readings till the rated secondary
TGG
current is reached
5. Remove the load and bring back the autotransformer to original position.
AD
V
RIER
AFE
N
6. Switch off the supply
X
Result:
Thus the load test on single phase transformer is conducted and its performance is
FR
A
N
CI
S
drawn.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
CO
LL
EG
E
CIRCUIT DIAGRAM FOR OPEN CIRCUIT TEST OF 1 TRANSFORMER
CI
S
X
AD
V
RIER
AFE
N
TGG
CIRCUIT DIAGRAM FOR SHORT CIRCUIT TEST OF 1 TRANSFORMER
FR
A
N
EQUIVALENT CIRCUIT REFERRED TO PRIMARY SIDE:
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 5
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:
Range
Type
Quantity
E
Name of the apparatus
EG
Sl.no
Ammeter
M.I
2.
Volt meter
MI.
3.
Watt meter
Dynamo meter
4.
Connecting wires
Formulae:
From open circuit test:
W0 = V0 I0 Cos 0 ( watts)
Cos 0 =
AD
V
W0
RIER
AFE
N
TGG
CO
LL
1.
X
V0 I0
CI
I = I0 Sin 0
S
I w = I0 Cos 0 ( Iron loss component)
( magnetizing component)
A
N
R0 = V0 / I w  (resistance to represent core loss)
FR
X0 = V0 / I
 (reactance to represent magnetizing component)
W0 = No load input = core loss = Wi = Iron loss
I0 - No load input current
V0 – No load rated input voltage
From short circuit test:
R01 =
Wsc 
Isc 2
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
TGG
CO
LL
EG
E
Model Graph
N
Open circuit test
Open circuit
primary voltage
(VOC) in Volts
AD
V
Open circuit primary
current (IOC)
In Amps
Open circuit power
Open circuit
(Woc) in Watts
Secondary
Observed
Actual voltage in volts
FR
A
N
CI
S
X
Sl.
no
RIER
AFE
multiplication factor:
Short Circuit Test
Sl.
No
multiplication factor:
Short circuit
primary current
(ISC)
In Amps
Short circuit
primary voltage
(VSC) in Volts
Short circuit power
(Wsc) in Watts
Observed
Actual
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Short circuit
Secondary
Current in Amps
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Z01
= Vsc 
X01
Isc
=  Z012 - R012 
R01 - equivalent resistance of transformer referred to primary side
X01 - equivalent reactance of transformer referred to primary side
Z01 - equivalent impedance of transformer referred to primary side
Wsc – Full load copper loss
EG
E
R02 = R01 x K 2
X02 = X01 x K 2
I2 R02 Cos + I2 X02 Sin X 100 %
TGG
V2
CO
% Regulation =
LL
Z02 = Z01 x K 2
+ lagging Power factor
Cos - Power factor
X * KVA * P.f
* 100 %
AD
V
Efficiency at various loads =
RIER
AFE
N
- leading powerfactor
X * KVA * P.f + Wi + X 2 Wsc
X
X – Load ratio
CI
S
Precautions:
FR
Procedure:
A
N
1. Auto transformer must be kept at minimum potential point
Open circuit test:
1. Make the connections as per the circuit diagram
2. Switch on the supply and vary the autotransformer to get rated voltage
3. Note down ammeter, voltmeter and wattmeter readings.
4. Bring back the autotransformer to original position.
5. Switch off the supply
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Determination of Efficiency:
Fracti
on of
load/
Load
factor
(X)
Copper loss
Output power
at various
Total loss
1000* ( X  KVA  Cos )
loads
in watts at Various P.F ( X 2  WSC ) in watts WT2=
(Woc ) +(X *Wsc)
in watts
0.4
0.6
0.8
* (100 ) in %
0.2
1
0.4 0.6 0.8 1
EG
E
0.2
Efficiency at Various
P.F
o/ p

o / p  WT
N
Load
factor
RIER
AFE
Determination of Regulation:
TGG
CO
LL
¼
½
¾
1
% V regulation at loads of
Leading p.f
0.2
0.4
0.6
0.8
% V regulation at loads of
Lagging p.f
0.2
0.4
0.6
0.8
FR
A
N
CI
S
X
AD
V
0.2
0.4
0.6
0.8
Unity
p.f
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Short circuit test:
1. Make the connections as per the circuit diagram
2. Switch on the supply and vary the autotransformer to get rated short circuit
current.
3. Note down ammeter, voltmeter and wattmeter readings.
E
4. Bring back the autotransformer to original position.
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
5. Switch off the supply
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FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Result:
Thus the OC and SC test was performed and thus the efficiency and regulation are
predetermined.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM FOR O.C AND S.C TESTSON 3 PHASE ALTERNATOR:
RIER
AFE
N
Tabulation:
Open circuit test:
If
(Amperes)
Open circuit voltage
E0( Volts)
A
N
CI
S
X
AD
V
Sl.No
FR
Short circuit test:
If2 (Amperes)
Isc (Amperes)
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 6 REGULATION OF ALTERNATOR BY EMF AND MMF METHOD
Date:
Aim:
To pre-determine the regulation of alternator by emf and mmf method.
Apparatus required:
Range
Type
Voltmeter
MI
2
Ammeter
MC,
3
Ammeter
MI
4
Rheostat
5
Connecting wires
CO
LL
1
EMF method
open circuit voltage
at constant field current
AD
V
Zs =
RIER
AFE
N
TGG
Wire wound
Formula:
S
CI
XS = √ ZS2 – Rac2
X
short circuit current
Rac = 1.6 x Ra
Quantity
E
Name
EG
SL.No.
A
N
ZS → Synchronous impedance (Ω)
XS → Synchronous Reactance (Ω)
FR
Rac → Effective Resistance
(Ω)
EO = √ (Vcosφ + IaRac)2 + (Vsinφ ± IaXS)2
( + → lagging p.f and - →leading p.f)
V → rated voltage ( volts)
Ia → rated armature current (volts)
Rac → effective resistance ( Ω)
Cosφ → power factor
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
LL
EG
E
Model Graph:
Eo
AD
V
Emf Method
leading
% Regulation
lagging
FR
A
N
CI
S
X
Cosφ
0
0.2
0.6
0.8
1
RIER
AFE
If
N
TGG
CO
Isc
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EE 6365 ELECTRICAL ENGINEERING LABORATORY
E0 – V
% Regulation = ---------- x 100 %
V
MMF Method
Ifr = √ If12 + If22 + 2 If1 If2 Cos (90±φ)
→ field current required to generate rated terminal voltage
If2
→ field current required to circulate rated short circuit current
Ifr
→ resultant field current
E0
→ The generated emf corresponding to Ifr (from graph)
LL
RIER
AFE
1. TPST switch must be kept open.
TGG
Precautions:
N
V
CO
E0 – V
---------- x 100 %
% Regulation =
EG
If1
E
{ + → lagging p.f and - →leading Pf}
2. Motor side rheostat must be kept in minimum position and alternator side
rheostat in maximum position.
AD
V
Procedure:
X
Open circuit test:
S
1. Make the connections as per the circuit diagram.
CI
2. Switch on the supply.
A
N
3. Start the motor –alternator set by using starter.
FR
4. Adjust the field rheostat of the motor to get the rated speed.
5. Increase the alternator field current in convenient steps and note down all the
meter readings upto 125% of the rated voltage.
6. Bring back the rheostat to the original position.
Short circuit test:
1. Close the TPST switch and adjust the potential divider such that the maximum
full load current flows through the armature winding.
2. Note down all the meter readings .
3. Bring back the rheostats to original position and switch off the supply.
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EE 6365 ELECTRICAL ENGINEERING LABORATORY
lagging
RIER
AFE
N
TGG
leading
CO
LL
EG
E
%Regn
AD
V
%Regn
S
X
MMF Method
%R
Ifr
Leading pf
E0
FR
A
N
Ifr
0
0.2
0.6
0.8
1
Lagging pf
E0
CI
Cosφ
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%R
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Result:
Thus the regulation of an alternator is predetermined using emf and mmf method.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
CIRCUIT DIAGRAM OF V AND INVERTED V CURVE OF SYNCHRONOUS
Tabulation:
At N= Ns (constant) VL =
AD
V
S
X
Armat
ure
Curre
nt (A)
W1OB
W1AC
W2ob
W2a
S
T
s
ct
CI
Load
Vrated
FR
A
N
Sl.
N
O.
Field
Curre
nt If
(A)
RIER
AFE
N
TGG
CO
LL
EG
E
MOTOR
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Power
W=
W1+W2
Power
Factor
= W/
(√3 *
VL *
IL )
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex No: 7
V & INVERTED V CURVES OF THREE PHASE SYNCHRONOUS
MOTOR
Date:
Aim:
To plot the V and Inverted V- Curves of the given Synchronous Motor at no-load
and on load.
Apparatus required:
Apparatus
Range
Type
Quantity
E
Sl.No.
Voltmeter
MI
2
Ammeter
MI
3
Wattmeter
Double Element
4
Tachometer
5
Connecting wires
CO
LL
EG
1
TGG
Analog
RIER
AFE
N
Formula:
Cos ф=Ia(min)/Ia
FR
A
N
CI
S
X
AD
V
PRECUTIONS:
1. Before giving the three phase supply, the three phase variac must be kept at its
minimum position.
2. Before providing d.c. supply to the field regulator of the motor, the field regulator
should be kept at minimum position and the field winding should be kept in open
position.
3. Start the synchronous machine preferably at no-load condition.
4. During the experiment the field current should not exceed 1.5 times the rated current of
the field current and the armature current/ ph (Ia ph) should not exceed 1.25 times the rated
armature current.
PROCEDURE:
1. Make connections as per the circuit diagram.
2. Keeping the field circuit of the synchronous motor open, close the TPST switch and
vary the auto transformer to obtain the rated three phase voltage. The machine will run at
a speed lesser than the synchronous speed. (with the help of damper windings as
induction motor)
3. Connect the field terminals of the synchronous motor to the d.c. supply by closing the
DPST switch and excite the field system. The machine will now begin to run at
synchronous speed by establishing magnetic locking between armature circuit and the
field system. Note down the field current, the corresponding armature current, line
voltage and wattmeter readings.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
Model Graph:
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
4. Vary the field current by adjusting the field excitation system and for each value of
field current (from low value of field current up to 1.5 times the rated field current) and
note down the corresponding meter readings.
5. Repeat the same procedure for various loading conditions carefully not exceeding 1.25
times the armature current and 1.5 times the rated field current.
Result:
Thus the v and inverted v curve of synchronous motor has been plotted at various
loads.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
RIER
AFE
N
TGG
CO
LL
EG
E
CIRCUIT DIAGRAM OF THREE PHASE INDUCTION MOTOR
S
CI
FR
A
N
Efficiency
Speed
Slip
Power factor
load current
Torque
X
AD
V
Model Graph:
Output power in watts
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
LOAD TEST ON 3φ SQUIRREL CAGE INDUCTION MOTOR
Ex.No: 8
Date:
Aim:
To determine the performance characteristics of the given 3φ squirrel cage induction
motor by conducting load test.
Voltmeter
2
Ammeter
3
Wattmeter
4
Tachometer
5
Connecting wires
EG
Type
MI
CO
1
Range
LL
Apparatus
Analog
AD
V
Formula:
Dynamometer
N
TGG
MI
RIER
AFE
Sl.No.
E
Apparatus required:
Input power
= W1 x MF1+ W2 x MF2 (watts)
X
Torque(T) = ( S1 ~ S2 ) x 9.81 x r (N-m)
= 2ΠNT / 60 watts
CI
S
Output power
= NS – N x 100 %
NS
FR
Slip
A
N
Efficiency = output power / input power x 100%
Multiplication factor =
VIcosφ
no. of divisions in the wattmeter
S1, S2= spring balance readings in Kg.
R = radius of the brake drum in m (circumference / 2Π)
N = Actual speed of the rotor in rpm
T = Torque
NS = Synchronous speed rpm
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Quantity
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Tabulation:
Speed of
the motor
(N)
voltage
(VL)
Act
ual
Observ
ed
Actual
Watts
Wat
ts
Watts
Watts
S1
rpm
Kg
S2
Kg
S1
~
S2
Kg
Torque
(T) =
(s1~s2
)* (R)*
(9.81)
N-m
Outpu
t
power
2NT/
60
Efficien
cy ()=
o/p / i/p
x 100
Slip
(S)=
{(Ns-N)
/ Ns}
x 100
%
%
Watts
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
Volts
Observe
d
Spring balance
reading
A
N
Amps
Load
Input power
(W2)
FR
S.
no
Load
current
(IL)
Input power
(W1)
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Power
factor
(cos)
=
i/p / VLIL
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
PF =
(W1 x MF1 + W2 x MF2)
√3VL IL
Precautions:
1. There should be no load at the time of starting.
2. Auto transformer must be kept at minimum position
Procedure:
E
1. Make the connections as per the circuit diagram.
EG
2. Switch on the supply and adjust the auto transformer to get the rated voltage and
LL
note down the no load readings.
3. Adjust the loads and for various loads note down the corresponding meters
CO
reading till the rated current is reached.
TGG
4. Unload the motor, bring back the auto transformer to minimum position and
RIER
AFE
N
switch off the supply.
AD
V
Result:
FR
A
N
CI
S
X
Thus the performance characteristics of the squirrel cage induction motor is
determined.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex. No: 9
SPEED CONTROL OF THREE PHASE SLIP RING INDUCTION
MOTOR
Date:
Aim:
To conduct the speed control test on three phase slip ring induction motor.
Apparatus Required:
Type
Quantity
E
Range
EG
Apparatus
1
Voltmeter
MI
2
Ammeter
3
Wattmeter
LL
Sl.No.
4
Tachometer
5
Connecting wires
MI
CO
Dynamometer
RIER
AFE
N
TGG
Analog
S
X
AD
V
Theory:
These motors are practically started with full line voltage applied across the stator
terminals, the value of starting current is adjusted by introducing the variable resistance
in the rotor circuit. The controlling resistance is in the resistance being gradually cut out
of the rotor circuit, as the motor attains rated speed. It has been already shown that by
decreasing rotor resistance, the motor attains rated speed and at the same time the starting
torque is also increased due to improvement in power factor.
FR
A
N
CI
Procedure:
1. Connections are made as per the circuit diagram.
2. Note down the resistance in each phase using Multimeter.
3. Switch ON the A.C power supply.
4. Then the speed of the motor is taken for each resistance per phase.
5. The graph was drawn between resistance and speed.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
CO
LL
EG
E
CIRCUIT DIAGRAM OF SPEED CONTROL OF SLIP RING INDUCTION
MOTOR
CI
FR
A
N
Model graph
S
X
AD
V
RIER
AFE
N
Rotor resistance
(Position Or Value)
Sl.no
TGG
Tabular Column:
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Speed in Rpm
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Result:
Thus the speed control on three phase slip ring induction motor is performed.
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
CO
LL
EG
E
CIRCUIT DIAGRAM OF LOAD TEST ON SINGLE INDUCTION MOTOR
Speed
(rpm)
I/P Power
(W)
Obs
Spring Balance
reading
N
IL
(A)
RIER
AFE
VL
(V)
Act
S1
S2
S1~S2
Torque
(Nm)
O/P
Power
(W)
A
N
CI
S
X
AD
V
Sl.
No.
TGG
Tabulation:
FR
Model Graph:
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%slip
%η
cosφ
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ex N0 : 10
LOAD TEST ON INDUCTION SINGLE PHASE INDUCTION
MOTOR
Date:
Aim:
To conduct the load test on the given single phase induction motor and to plot its
performance characteristics.
Apparatus Required:
Apparatus
Range
Type
Voltmeter
MI
2
Ammeter
MI
3
Wattmeter
Dynamometer
4
Tachometer
Analog
5
Connecting wires
1. Torque, T= 9.81 (S1 ~ S2) R
RIER
AFE
N
TGG
CO
LL
EG
1
Formula:
(Nm)
S
X
AD
V
where R=(r + t /2) (m)
R---effective radius of the brake drum (m)
r--- Radius of the braked drum (m)
t---thickness of the belt (m)
A
N
CI
2. Output power, Po = 2πNT/60 (W)
where N- actual speed of the motor (rpm)
FR
3. Input power Pi = W (W)
where W- actual reading of the wattmeter reading (W)
4. % Slip S= (Ns-N)/Ns x 100 (%)
Where Ns-Synchronous speed (rpm), N=1500 rpm.
5. Power factor cosφ =Pi / (V * I)
where V-line voltage (V)
I-line current (A)
6. Efficiency %η = (Po/Pi) x 100 (%)
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Quantity
E
Sl.No.
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
7. Multiplication Factor (MF) of the wattmeter:
MF= (Current Coil Rating * Pressure Coil Rating * Power Factor)/ Full Scale Deflection
of the wattmeter
8. Ns = 120 * f/ P
Where f is the frequency of the supply (or) stator frequency
P is the no. of poles of the motor
EG
E
Precautions:
1. Before starting the motor, release the load completely.
2. Before providing a.c supply, the single phase variac must be in the minimum position.
3. Handle the tachometer carefully.
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
Procedure:
1. Make the connections as per the circuit diagram. Release any load available on the
motor. Switch ON the power supply by closing DPST switch.
2. Vary the single phase auto transformer for rated input voltage.
3. Initially when the motor is unloaded, note the readings of ammeter, voltmeter and
wattmeter. Measure the speed using a tachometer at this no load condition.
4. Load the motor in gradual steps up to the rated current. At each step, note down all the
above mentioned readings.
5. Add cooling water to the brake drum as and when required when the motor is loaded.
6. Release the load on the motor and bring the auto transformer to initial position.
7. Switch OFF the supply.
8. Measure the circumferential length of the brake drum and use the same for calculation
of the radius ‘R’ of the brake drum.
Result:
Thus the load test on single phase induction motor is performed and its
performance characteristics are drawn.
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FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Fig.1
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Ext No: 11
Date
STUDY OF D.C & A.C MOTOR STARTERS
Aim:
To study the different kinds of D.C &A.C motor starters
Appartus Required:
EG
E
Quantity
1
1
1
1
1
1
1
LL
CO
TGG
Name of the apparatus
Two Point starter
Three Point starter
Four Point starter
DOL Starter
Auto transformer Starter
Star-Delta Starter
Rotor Resistance Starter
RIER
AFE
N
Sl No.
1
2
3
4
5
6
7
Theory :
CI
S
X
AD
V
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 .
FR
A
N
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 from dangerous high speed.
ii) It protects the motor from overloads.
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RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
FR
A
N
CI
S
X
AD
V
Fig 2
Fig 3
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
Two Point Starters: ( Refer Fig 1)
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 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.
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
(i)
Four Point Starter: (Refer Fig 3)
X
(iii)
FR
A
N
CI
S
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.
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FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
LL
EG
E
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
STUDY OF INDUCTION MOTOR STARTERS
TGG
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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
mornal 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.
(Ref. To text book for fig)
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.
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
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.
(Ref. To text book for fig)
Full Voltage Or Direct –On-Line Starting:
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.
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FR
A
N
CI
S
X
AD
V
RIER
AFE
N
TGG
CO
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FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
[Type text]
www.nitropdf.com
http://www.francisxavier.ac.in
FRANCIS XAVIER ENGINEERING COLLEGE, TIRUNELVELI
EE 6365 ELECTRICAL ENGINEERING LABORATORY
CO
LL
EG
E
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 ampereturns. 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 directon-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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Result:
FR
A
N
CI
S
X
AD
V
RIER
AFE
N
Thus the construction and working of different starters for starting D.C series,
shunt, compound and three phase induction motors are studied.
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