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EE 706
ELECTRICAL MACHINES LABORATORY II
2006 Scheme
July 5, 2010
ACKNOWLEDGEMENTThis manual is the result of contributions from the following staff members.
Ms. Sheena K. M.Mr. Anith KrishnanMr. Naveen T. R.Mr. Jobira j C.Mr. Mano j M. S.Mr. Gireesh G.Mr. Vaishak L. S.
INTRODUCTIONA few words about the lab.
INSTRUCTIONS• All students should wear shoes.
• Male students should tuck in their shirts.
• Female students should tie up their hair properly.
• Students should not lean on the work bench.
• Do not switch on the supply before the circuit is verified by the concerned lab faculty.
• Use of mobile phone inside the laboratory is strictly prohibited.
All the students are to strictly abide by the instructions given here and any additional instruction given during the lab session, failing to which he/she will have to face disciplinary action.
Contents
Load test on SCIM. 1
No load and blocked rotor test on SRIM. 4
Load test on single phase induction motor 9
Alternator regulation by direct loading. 11
Alternator regulation by indirect method 13
V curves and inverted V curves of synchronous motor 18
No load and blocked rotor test on SCIM. 21
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 1
LOAD TEST ON SQUIRREL CAGE INDUCTION MOTOR
Aim:
To study the performance of the machine when loaded and to plot the following charac- teristics of a squirrel cage induction motor.
η Vs o/p N Vs o/p Ia Vs o/pcos φ Vs o/p%s Vs o/p
Machine details:
Refer name plate of the machine.
Precautions:
1. All the connections should be tight.2. The autotransformer should be in minimum position initially.3. The motor should be on no load at the time of starting.
Procedure:
1. Make the connections as shown in the circuit diagram.2. After taking care of the precautions, switch on the supply.3. Adjust the autotransformer till rated voltage is applied across the motor terminals.4. Note down all the meter readings in no-load condition.5. Increase the load in steps until the ammeter reads the rated current and note down
all the meter reading for each applied load.6. Reduce the load to zero, bring the autotransformer to the minimum position and
switch off the supply.
Division of Electrical Engineering, S.O.E., CUSAT 1
3
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Circuit Diagram:
zH0,5 V044
Observation Table:
Sl.No.
V1
(V)A1
(A)W1
(W)W2
(W)N
(rpm)S1
(kg)S2
(kg)i/p(W)
T(Nm)
o/p(W)
cos φ %s η
123456
Division of Electrical Engineering, S.O.E., CUSAT 2
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Equations and Calculations:
Voltage V = . . . . . . V Current I = . . . . . .
A W1 = . . . . . . WW2 = . . . . . . W
I/P power = W1 + W2 = . . . . . . W Speed N = . . . . . . rpm
S1 = . . . . . . kgS2 = . . . . . . kg
Torque T = (S1 − S2)rg = . . . . . . Nm2πN T
O/P power =60
= . . . . . . W
Power Factor cos φ = . . . . . .
Slip s = Ns − N
Ns
O/P
× 100 = . . . . . . %
Efficiency η =I/P
× 100 = . . . . . . %
Here r is the radius of the break drum and g is the acceleration due to gravity.
Result:
Division of Electrical Engineering, S.O.E., CUSAT 3
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 2
NO LOAD AND BLOCKED ROTOR TEST ON SLIP-RING INDUCTION MOTOR
Aim:
To conduct no load and blocked rotor test on slip-ring induction motor and to draw its equivalent circuit and circle diagram.
Machine Details:
Refer name plate of the machine.
Precautions:
1. The autotransformer should be in minimum position while switching on the supply.2. The motor should not be on load while starting.
Procedure:
No-load test
1. After taking care of the precautions, switch on the supply.2. Adjust the autotransformer gradually such that the rated voltage is applied to the
stator.3. Note down all the meter readings under no-load condition.4. Reduce the autotransformer to minimum position.5. Switch off the supply.
Bl o ck ed rotor test
1. After taking care of the precautions, switch on the supply.2. Adjust the autotransformer till the rated current flows through the stator.3. Take all the meter readings.4. Reduce the autotransformer to minimum position.5. Switch off the supply.
Division of Electrical Engineering, S.O.E., CUSAT 4
,
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Circuit Diagram:
zH0,5V044
Figure 1: Circuit diagram for no-load test.
Figure 2: Circuit diagram for blocked rotor test.
C D V03
Figure 3: Measurement of stator resistance.
Division of Electrical Engineering, S.O.E., CUSAT 5
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Observation Table:
No-load test
Sl.No.
V0
(V)I0
(A)W1
(W)W2
(W)W0
(W)123456
Blocked rotor test
Sl.No.
Vsc
(V)Isc
(A)W1
(W)W2
(W)Wsc
(W)123456
Stator Resistance
Sl.No.
V(V)
I(A)
Ra = 1 × V2 I
(Ω)123456
Division of Electrical Engineering, S.O.E., CUSAT 6
0
I0
3R =
Z − R
0
2
0
I
1
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Equations and Calculations:
From no-load test
Supply voltage V0 = . . . . . . V Circuit current I0 = . . . . . . A
No-load power W0 = W1 + W2 . . . . . . WW0cos φ0 = √3V I
= . . . . . .
Magnetising current Iµ = I0 sin φ0 = . . . . . . A Working current Iw = I0 cos φ0 = . . . . . . A
V0R0 =w
= . . . . . . Ω
From blocked rotor test
X = V0
µ= . . . . . . Ω
Supply Voltage Vsc = . . . . . . V Circuit current Isc = . . . . . . A
Power consumed Wsc = W1 + W2 = . . . . . . WVscZ01 = Isc
= . . . . . . Ω
Wsc01 2
sc= . . . . . . Ω
√ X01 = 2 2
01 01 = . . . . . . Ω
From stator resistance test
6∑DC resistance Rdc =
6Sl.N o.=1
Ra = . . . . . . Ω
AC resistance Rac = 1.2 × Rdc = . . . . . .
Ω Rest of the parameters can be calculated as
R2 = R01 − Rac = . . . . . . Ω
X1 = X 0
=
X01
2= . . . . . . Ω
Division of Electrical Engineering, S.O.E., CUSAT 7
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
2 X 0R1 X1 R0
2
R0 X0 R0 (
1)
2 s − 1
Figure 4: Equivalent Circuit.
Figure 5: Circle Diagram.
Result:
Division of Electrical Engineering, S.O.E., CUSAT 8
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 3
LOAD TEST ON SINGLE PHASE INDUCTION MOTOR
Aim:
To conduct load test on a single phase induction motor and to plot the following charac- teristics.
η Vs o/p N Vs o/p Ia Vs o/pcos φ Vs o/p%s Vs o/pT Vs o/p
Machine details:
Refer name plate of the machine.
Precautions:
1. All the connections should be tight.2. The motor should not be on load while starting.
Procedure:
1. Close DPST and start the motor on no load at rated voltage.2. Note down all the meter readings at no load.3. Gradually apply the load in steps till the ammeter reads rated current. Note down
all the meter readings for each load.4. Gradually decrease the load to zero and switch off the supply.
Circuit Diagram:
.
.CA z H0,5V032
Division of Electrical Engineering, S.O.E., CUSAT 9
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Observation Table:
Sl.No.
V1
(V)A1
(A)W1
(W)N
(rpm)S1
(kg)S2
(kg)T
(Nm)o/p(W)
cos φ η
123456
Equations and Calculations:
Voltage V = . . . . . . V Current I = . . . . . . AI/P power = W1 = . . . . . .
W Speed N = . . . . . . rpmS1 = . . . . . . kgS2 = . . . . . . kg
Torque T = (S1 − S2 )rg = . . . . . . Nm2πN T
O/P power =60
= . . . . . . W
Power Factor cos φ = . . . . . .O/PEfficiency η =I/P
× 100 = . . . . . . %
Here r is the radius of the break drum and g is the acceleration due to gravity.
Result:
Division of Electrical Engineering, S.O.E., CUSAT 10
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 4
ALTERNATOR REGULATION BY DIRECT LOADING
Aim:
To determine the regulation of a 3φ alternator by direct loading and to plot the following graphs.
Machine Details:
Refer name plate of the machine.
Precautions:
1. The field rheostat of D.C. motor should be kept at minimum position and that of the alternator should be at maximum position while starting the experiment.
2. All the switches should be in open position before giving the supply.
Procedure:
1. Wire up the circuit as shown in the circuit diagram.2. DC supply is given to the prime mover by closing DPST and is started using the
starter.3. By varying the field rheostat, the prime mover is made to run in the rated speed of
the alternator.4. Close SPST to energize the field of alternator.5. Adjust the alternator field rheostat so as to get rated voltage across the alternator
open circuited terminals.6. Close TPST switch (the alternator is now connected to the load).7. Add some load to the alternator. This causes the terminal voltage to change (it can
decrease or increase).8. Adjust the alternator field rheostat such that the rated voltage is applied across the
load. Note down the ammeter readings.9. The entire load is now thrown off the alternator by bringing the TPST switch to the
open position.10. The open circuit or no-load voltage (E0) is noted.11. Repeat 7-10 until the ammeter reads the rated current of the machine.12. De-energise the alternator field and switch off the supply.
Division of Electrical Engineering, S.O.E., CUSAT 11
SPD
C T
T
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Circuit Diagram:
.
. S D T P V022
Observation Table:
Sl.No.
VL
(V)IL
(A)If
(A)E0
(V)Regulation
(%)123456
Equations and Calculations:
Voltage across the load VL = . . . . . . V Load current IL = . . . . . . A Field current If = . . . . . . A
% Regulation = E0 − VL
VL
× 100 = . . . . . . %
where E0, VL , IL and If are per-phase values.
Result:
Division of Electrical Engineering, S.O.E., CUSAT 12
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 5
ALTERNATOR REGULATION BY INDIRECT METHOD
Aim:
To pre-determine the regulation of a 3φ alternator by indirect methods at different loads( 1 3
4 ,
4 and full load) for various power factors (0.8 lead, 0.8 lag, upf ) and draw the regulation
vs. load current curve by conducting suitable tests.
Machine Details:
Refer name plate of the machine.
Precautions:
1. All the switches should be in open position before switching on the supply.2. The field rheostat of D.C. motor should be kept at minimum position and that of
the alternator should be at maximum position while starting the experiment.
Procedure:
OC T est
1. Wire up the circuit as shown in the circuit diagram.2. DC supply is given to the prime mover by closing DPST and is started using the
starter.3. By varying the field rheostat, the prime mover is made to run in the rated speed of
the alternator.4. Close SPST to energize the field of alternator.5. By adjusting the alternator field rheostat, increase the alternator field current in
steps and note down If and open circuit voltage E0.6. Repeat the above step till the voltmeter reads 1.25 times the rated voltage of the
machine.7. De-energise the alternator field and switch off the supply.
SC T est
1. Wire up the circuit as shown in the circuit diagram.2. DC supply is given to the prime mover by closing DPST and is started using the
starter.3. Close SPST switch such that the alternator is now short-circuited.4. By varying the field rheostat, the prime mover is made to run in the rated speed of
the alternator.
Division of Electrical Engineering, S.O.E., CUSAT 13
SPD
SPD
C T
T
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
5. Close SPST to energize the field of alternator.6. By adjusting the alternator field rheostat, increase the alternator field current in
steps and note down If and the armature current Ia .7. Repeat the above step till the ammeter reads 1.25 times the rated current of the
machine.8. De-energise the alternator field and switch off the supply.
Circuit Diagram:
OC Test
.C.D TV022
SC Test
.
. S D T P V022
Division of Electrical Engineering, S.O.E., CUSAT 14
SC TestSl.No.
If(V)
Ia
(A)1.2.3.4.5.6.
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Resistance measurement
C D V03
Observation Table:
OC TestSl.No.
E0
(V)If
(A)1.2.3.4.5.6.
Resistance Measurement
Sl.No.
V(V)
I(A)
Rdc
(Ω)123456
Division of Electrical Engineering, S.O.E., CUSAT 15
t
o o
Is
e
CT
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Sample Graph:
V) ) (
(A se
stT CO Sm m rf fr0
Ia
Equations and Calculations:
EMF Meth o d
Synchronous Impedance Z = E0
sc= . . . . . . Ω
1AC resistance of armature Ra = 1.2 × 6
1. Lagging p.f.
6∑
Sl.N o.=1
Rdc = . . . . . . Ω
2. Unity p.f.
E0 = √
(V cos φ + I Re)2 + (V sin φ + I Xs
)2
E0 = √
(V + I Re)2 + (I Xs)2
Division of Electrical Engineering, S.O.E., CUSAT 16
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
3. Leading p.f.
MMF Meth o d
E0 = √
(V cos φ + I Re )2 + (V sin φ − I Xs )2
The students are expected to complete this section by themselves and write it in the laboratory record.
Result:
Division of Electrical Engineering, S.O.E., CUSAT 17
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 6
V CURVES AND INVERTED V CURVES OF SYNCHRONOUS MOTOR
Aim:
To obtain V and inverted V curves of the given synchronous motor.
Machine Details:
Refer name plate of the machine.
Precautions:
1. Synchronizing switch should be in open position.2. The synchronous machine field regulator should be in maximum resistance position
at the time of starting.3. The DC machine field regulator should be in minimum resistance position at the
time of starting.4. DPST and SPST switch should be in open position before giving supply to the circuit.5. DPDT switch should be position 1-1 when supply is switched on.
Procedure:
1. Close the DPST switch and start the DC machine by cutting down the starter resis- tance.
2. Adjust the field regulator of DC motor and drive the synchronous machine in syn- chronous speed.
3. Close TPST switch and note down the supply voltage level using voltmeter Vs.4. Close SPST switch and increase the field current of the synchronous machine such
that the terminal voltage becomes the same as supply voltage i.e., VL=Vs .5. Observe the manner in which the lamps (across the synchronizing switch) are glowing.6. If the 3 sets of lamps become bright and dark one after another (indicating wrong
phase sequence) bring the TPST switch to open position.7. Bring the field rheostat of the synchronous machine to minimum position.8. Open SPST switch and interchange any two terminal connection on the TPST switch.
Follow steps 4 and 5.9. If the 3 sets of lamps become bright and dark simulataneously, the phase sequence is
correct.10. Reduce the rate of flickering of synchronizing lamps as low as possible by adjusting
the DC motor field energizing rheostat.
Division of Electrical Engineering, S.O.E., CUSAT 18
3SPD C
M
MV
0V
z0
00
4
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
11. Close the synchronizing switch at the middle of the dark period of the lamps.12. Open DPDT switch. The synchronous machine will now work as synchronous motor
and the DC machine will work as a self-excited DC shunt generator.13. For this no load position, the exciting field current of synchronous motor is varied
in steps till the ammeter reads the rated line current. The meter readings are noted down for each field current.
14. Put the switch to 2-2 position and apply a constant load by using loading rheostatRL .
15. Vary the field current and note down the field current and armature current. Repeat the same for different loads.
Circuit Diagram:
.C. C H
D T ) ,5V5
2 ‐3 12 ) (0
A0‐2(0
Observation Table:
No Load Load Current = . . . . . .ASl.No.
Ia
(A)If
(A)I/P(W) cos φ
Ia
(A)If
(A)I/P(W) cos φ
1.2.3.4.5.6.
Division of Electrical Engineering, S.O.E., CUSAT 19
L a
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Equations and Calculations:
Armature Current Ia = . . . . . . A Field Current If = . . . . . . A
I /PPower Factor cos φ = √3V I
= . . . . . .
Result:
Division of Electrical Engineering, S.O.E., CUSAT 20
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Experiment No.: 7
NO LOAD AND BLOCKED ROTOR TEST ON SQUIRREL CAGE INDUCTION MOTOR
Aim:
To conduct no load and blocked rotor test on squirrel cage induction motor and to draw its equivalent circuit and circle diagram.
Machine Details:
Refer name plate of the machine.
Precautions:
1. The autotransformer should be in minimum position while switching on the supply.2. The motor should not be on load while starting.
Procedure:
No Load T est
1. After taking care of the precautions, switch on the supply.2. Adjust the autotransformer gradually such that the rated voltage is applied to the
stator.3. Note down all the meter readings under no-load condition.4. Reduce the autotransformer to minimum position.5. Switch off the supply.
Bl o ck ed rotor test
1. After taking care of the precautions, switch on the supply with the rotor blocked.2. Adjust the autotransformer till the rated current flows through the stator.3. Take all the meter readings.4. Reduce the autotransformer to minimum position.5. Switch off the supply.
Division of Electrical Engineering, S.O.E., CUSAT 21
3
3
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Circuit Diagram:
zH0,5 V044
Figure 6: Circuit diagram for no-load test.
zH0,5 V044
Figure 7: Circuit diagram for blocked rotor test.
C D V03
Figure 8: Measurement of stator resistance.
Division of Electrical Engineering, S.O.E., CUSAT 22
Lab Manual: Electrical Machines Laboratory II (EE 706) 2006 Scheme
Observation Table:
No-load test
Sl.No.
V0
(V)I0
(A)W1
(W)W2
(W)W0
(W)123456
Blocked rotor test
Sl.No.
Vsc
(V)Isc
(A)W1
(W)W2
(W)Wsc
(W)123456
Stator Resistance
Sl.No.
V(V)
I(A)
Ra
(Ω)123456
Division of Electrical Engineering, S.O.E., CUSAT 23