Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
Cycle 2
EE6512 Electrical Machines II Lab Manual
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
CIRCUIT DIAGRAM FOR SLIP TEST
3 Point Starter
L
F
A
350Ω,
2A
180V
DC SUPPLY
NAME PLATE DETAILS:
3Ф alternator
Volts:
DC shunt motor
Volts:
Amps:
Amps:
kVA:
kW:
RPM:
RPM:
FUSE RATING:
125% of rated current (full load current)
For DC shunt motor :
…………….
For Alternator
:
…………….
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
REGULATION OF THREE PHASE SALIENT POLE ALTERNATOR BY SLIP TEST
AIM:
The aim of the experiment is to predetermine the regulation of three phase salient pole
alternator by conducting the slip test.
APPARATUS REQUIRED:
S.NO
NAME OF THE
RANGE
TYPE
QUANTITY
APPARATUS
1.
Ammeter
(0-5) A
MI
1
2.
Ammeter
(0-5) A
MC
1
3.
Voltmeter
(0-150) V
MI
1
4.
Voltmeter
(0-150)V
MC
1
5.
Rheostat
300Ω,1.5A
Wire wound
1
6.
3 Ф Auto transformer
1
7.
Tachometer
1
8.
Connecting wires
As required
FORMULAE USED:
1. Armature Resistance, Ra =1.6 X Rdc
2. Direct impedance per phase (Zd) =
Vmin
in Ω
I max
3. Quadrature axis impedance per phase (Zq) =
4. Direct axis reactance per phase (Xd) =
Z
2
d
5. Quadrature axis reactance per phase (Xq) =
6. Percentage Regulation =
Vmax
in Ω
I min

 Ra2 in Ω
Z
2
q
 Ra2

in Ω
E0  Vrated
100
Vrated
7. E0  Vt cos  I q Ra  I d X d (for Motoring)
8. E0  Vt cos  I q Ra  I d X d (for Generating)
9.      (for Generator)
10.     (for Motor)
 Vt sin   I a X q 
 { +
 Vt cos  I a Ra 
11.   tan1 
For generating mode; -- For Motoring mode}
THEORY:
In non salient pole alternators air gap length is constant and reactance is also constant. Due to
this the MMFs of armature and field act upon the same magnetic circuit all the time hence can be
added vectorically. But in salient pole alternators the length of the air gap varies and reluctance
also varies. Hence the armature flux and field flux cannot vary sinusoid ally in the air gap. So the
reluctance of the magnetic circuit on which mmf act is different in case of salient pole
alternators. This can be explained by two reaction theory.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
PRECAUTIONS:
1. The motor field rheostat should be kept in minimum resistance position.
2. The alternator field should be kept open throughout the experiment.
3. The direction of rotation due to prime mover and due to the alternator run as the
motor should be same.
4. Initially all the switches are kept open.
PROCEDURE:
1. Connections are given as per the circuit diagram and confirm that the alternator filed
is in open condition.
2. Give the supply by closing the DPST switch.
3. Using the three point starter start the motor to run at the synchronous speed by
varying the motor field rheostat.
4. Apply 20% to 30% of the rated voltage to the armature of the alternator by adjusting
the autotransformer.
5. To obtain the slip and maximum oscillations of pointers, the speed is reduced slightly
lesser than the synchronous speed.
6. Note down the maximum current, minimum current, maximum voltage and minimum
voltage. Find out the direct and quadrature axis impedance (Zd,Zq).
TABULATIONS:
a. To find Zd and Zq :
S.No
Vmax
Vmin
Imax
Imin
b. To predetermine % Regulation:
% Regulation
S.No
Powerfactor
1
0.2
2
0..4
3
0.6
4
0.8
Lagging
Leading
Unity
GRAPH:
i. Powerfactor Vs Percentage Regulation
RESULT:
Thus the percentage regulation of the given three phase alternator is predetermined using
slip test.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
Circuit Diagrams for Negative Sequence and Zero Sequence Impedances of Salient Pole Alternator
3 POINT STARTER
L
F
(0-10)A,MI
A
+
R
N
M
S
P
B
Y
A2
Y
415V,
50Hz
T
F2
415V,
50Hz
T
V
S
A1
(0-300)V,MI
F1
S
350Ω, 2A
R
D
P
220V,
DC
T
S
A
F2
F1
B
A
-
(0-2)A,MI
N
NEGATIVE SEQUENCE IMPEDANCE
415/(0-470)V,
3ϕ VARIAC
Name Plate Details:
D.C Shunt Motor
kW : …………………………..
3 Phase Alternator
kVA : …………………………..
Speed: …………………………RPM
Speed: …………………………RPM
Voltage: ……………………….V
Voltage: ……………………….V
Current : ……………………….A
Current : ……………………….A
Field Voltage: ………………….V
Field Voltage: ………………….V
Field Current : ………………….A
Field Current : ………………….A
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
3 POINT STARTER
L
F
(0-10)A,MI
A
+
R
A
S
B
A2
F2
F1
D
Y
415V,
50Hz
T
Y
F2
415V,
50Hz
T
P
S
N
M
(0-300)V,MI
350Ω, 2A
S
V
S
T
A1
F1
P
220V,
DC
R
B
A
(0-2)A,MI
-
N
415/(0-470)V,
3ϕ VARIAC
ZERO SEQUENCE IMPEDANCE
TABULATION:
Negative Sequence
S.No
V
I
Zero Sequence
Z2=V/I
S.No
V
I
Z0=3V/I
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
MEASUREMENTS OF NEGATIVE SEQUENCE AND ZERO SEQUENCE IMPEDANCE OF
ALTERNATORS.
AIM:
To measure the negative and zero sequence impedances of the given salient pole
alternator.
APPARATUS REQUIRED:
S.NO
NAME OF THE
RANGE
TYPE
QUANTITY
APPARATUS
1.
Ammeter
(0-5) A
MI
1
2.
Ammeter
(0-2) A
MC
1
3.
Voltmeter
(0-300) V
MI
1
4.
Rheostat
300Ω,1.5A
Wire wound
1
5.
3 Ф Auto transformer
--1
6.
Tachometer
-Digital
1
7.
Connecting wires
--As required
THEORY:
When a synchronous generator is carrying an unbalanced load its operation may be
analyzed by symmetrical components. In a synchronous machine the sequence current produce
an armature reaction which is stationary with respect to reactance and is stationary with respect
to field poles. The component currents therefore encounter exactly same as that by a balanced
load as discussed. The negative sequence is produced and armature reaction which rotates around
armature at synchronous speed in direction to that of field poles and therefore rotates part the
field poles at synchronous speed. Inducing current in the field damper winding and rotor iron.
The impendence encountered by the negative sequence is called the – ve sequence impedance of
the generator. The zero sequence current produce flux in each phase but their combined armature
reaction at the air gap is zero. The impedance encountered by their currents is therefore different
from that encountered by + ve and –ve sequence components and is called zero sequence
impedance of generator.
Negative sequence:
The –ve sequence impedance may be found by applying balanced –ve sequence voltage
to the armature terminals. While the machine is drive by the prime mover at its rated
synchronous speed with the field winding short circuited. The ratio of v/ph and Ia/ph gives –ve
sequence Z/ph. The reading of the wattmeter gives I2 R losses. This loss /ph divided by Iph
required gives the –ve sequence R/ph from the impedance and reactance/ph. –ve sequence can be
calculated. Another method of measuring –ve sequence reactance is found to be connect the arm
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
terminals. The machine is driven at synchronous speed and field current adjusted until rated
current flows in the phases shorted through armature and current coil of wattmeter respectively
Zero sequence:
The sequence impedance may be determined by the connecting the armature windings of
the three phase in series and then connecting them to the single phase source of power. If the
machine is driven at synchronous speed with field winding shorted, then ZO=V/3I practically the
same results will be obtained with rotor stationary.
If windings are connected in parallel, then
PROCEDURE:
For Negative Sequence :
i. Make connection as shown in circuit diagram.
ii. Run DC motor with synchronous speed.
iii. Keeping the speed constant, vary the excitation and measure the voltmeter, ammeter and
wattmeter reading.
iv. Take 3-4 readings for different excitation.
v. The excitation should not be increased beyond the rated capacity of synchronous machine i.e.
6.9 A
For Zero Sequence:
i. Make connection as shown in circuit diagram.
ii. Set the autotransformer output to zero volts and switch on the supply.
iii. Gradually increase input voltage and note the ammeter reading for the voltage applied.
iv. Repeat reading upto the rated current rating of the machine (i.e, 6.9A).
RESULT:
Thus the negative and zero sequence impedances of the salient pole alternator is
measured.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
SEPARATION OF NO LOAD LOSSES OF THREE PHASE INDUCTION MOTOR
AIM:
To separate the no load losses of a 3 phase squirrel cage induction motor as iron losses
and mechanical losses.
NAME PLATE DETAILS:
3Ø Induction motor:
HP:
……………… HP
Voltage :
………………..V
Current :
………………..A
Speed: :
………………… RPM
FUSE RATING:
No load
:
10% of rated current (full load current).
APPARATUS REQUIRED:
S.NO
1.
2.
3.
4.
5.
6.
NAME OF THE
APPARATUS
Ammeter
Voltmeter
Wattmeter
3 Ф Auto transformer
Tachometer
Connecting wires
RANGE
TYPE
QUANTITY
(0-5) A
(0-600) V
600Ω,5A
415/(0-470)V
---
MI
MI
LPF
-Digital
--
1
1
2
1
1
As required
PRECAUTIONS:
i. The autotransformer should be kept in minimum voltage position.
ii. The motor should not be loaded throughout the experiment.
PROCEDURE:
i. Connections should be made as per the circuit diagram.
ii. Start the motor by giving three phase supply.
iii. Vary the autotransformer till rated speed is attained and note the input power, voltage and
current.
iv. Repeat the same procedure for and tabulate the reading.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
v. Find the stator copper loss and constant loss by respective formulas.
vi. Draw the suitable graph to find the mechanical losses.
vii. Obtain the core los by separating the mechanical loss from constant losses.
GRAPH:

The graph drawn between constant losses (watts) and input voltage(volts).
MODEL CALCULATIONS:
1.
Input power (W) =(W1+W2)in watts
2.
Stator copper loss =3I2Rs in watts
3.
Constant loss/phase (Wc)= (W-3I2Rs)/3 in watts
4
Core loss/phase (Wi)= (constant loss/phase)-mechanical loss
TABULTAION:
S.No
V
I
W1
W2
W
Stator Cu
Loss
Constant
Loss per
Phase
(Wc)
Core
Loss per
Phase
(Wi)
RESULT:
Thus the no load losses of 3-phase squirrel cage induction motor was separated as core
losses and mechanical losses.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
NO LOAD TEST
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
NO LOAD AND BLOCKED ROTOR TEST ON SINGLE PHASE INDUCTION MOTOR
AIM:
To draw the performance characteristics of a single phase induction motor by conducting
the no-load and blocked rotor test.
APPARATUS REQUIRED:
S.No
1
2
3
4
5
6
7
Name of Apparatus
Voltmeter
Voltmeter
Ammeter
Ammeter
Wattmeter
Wattmeter
Connecting wires
Range
(0-300)V
(0-150)V
(0-10)A
(0-2)A
(330V,10A)
(300V,5A)
--
Type
Qty.
MI
MI
MI
MI
UPF
LPF
--
1
1
1
1
1
1
As reqd.
FUSE RATING:
125% of ……..A= ………..A
THEORY:
A 1-Ф induction motor consists of stator,rotor and other associated parts.In the rotor of a single
phase winding is provided.The windings of a 1- Ф winding(provided) are displaced in space by
120º.A single phase current is fed to the windings so that a resultant rotating magnetic flux is
generated.The rotor starts rotating due to the induction effect produced due to the relative
velocity between the rotor winding and the rotating flux.
PRECAUTIONS:
No load test:
 Initially TPST Switch is kept open. 
 Autotransformer is kept at minimum potential position. 
 The machines must be started on no load. 
BLOCKED ROTOR TEST:



Initially the TPST Switch is kept open. 
Autotransformer is kept at minimum potential position. 
The machine must be started at full load (blocked rotor). 
PROCEDURE:
NO LOAD TEST:
1. Connections are given as per the circuit diagram.
2. Precautions are observed and the motor is started at no load.
3. Autotransformer is varied to have a rated voltage applied.
BLOCKED ROTOR TEST:
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Dhanalakshmi Srinivasan Institute of Technology, Samayapuram, Trichy.
1.
2.
3.
4.
Connections are given as per the circuit diagram.
Precautions are observed and motor is started on full load or blocked rotor position.
Autotransformer is varied to have rated current flowing in motor.
Meter readings are the noted.
FORMULAE USED:
Re = 1.6XRdc
1. No Load Test:
 cos Ф = W0/V0I0 
 Iw = I0 cosФ 

 Im = I0sin Ф 
 R0 = V0/Iw 
 X0 = V0/Im 

2. Blocked Rotor Test:
o Zsc = Vsc/Isc Ω
o Rsc = Wsc/Isc2 Ω
o Xsc = √(Zsc2 – Rsc2) Ω
TABULATION
NO LOAD TEST
S.No.
Vo(volts)
Io(amps)
m.f
Wo(watts)
Observed Acual
m.f
Wsc(watts)
Observed Actual
BLOCKED ROTOR TEST
S.No.
Vsc(volts)
Isc(amps)
RESULT:
Thus the no load and blocked rotor test on the single phase induction motor has been
conducted and the equivalent circuit has been drawn.
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