EEP 303 lab report

1. EEP303 Laboratory
Determination of Positive, Negative and Zero-
Sequence Reactance of Synchronous Machine
12/2/13
Indra Bhushan 2010EE50548
Umang Gupta 2010EE50564
Vivek Mangal 2010EE50566
Mehul Mittal 2010EE50553
Srishti Mahajan 2010EE561
Ciddhi Jain 2010EE50511

2. Aim: To determine experimentally positive-, negative-, and zero-sequence reactance of
a synchronous machine.
Theory:
A three phase unsymmetrical system can be broken resolved to 3-three phase
symmetric systems and can be analysed. This eases the mathematical formulation and
analysis. In general, an n- phase unsymmetrical system can be broken resolved to n
number of n phase symmetric systems and can be analysed. In case of three phase
system they are called – positive, negative and zero sequence network.
The positive sequence has three phase symmetry and has RYB phase sequence, negative
sequence has RBY and zero sequence has equal magnitude and phase. All three phase
unsymmetrical system can be analysed by resolving with the sequence networks. These
sequences do not interact with each other (orthogonal).
Different parameters are associated with different phase sequences and hence one has
to find them to characterise them.
We find these parameters by making current of a particular sequence flow and finding
the impendences.
Observations:
Determination of X1
a. Open circuit test:
Ie (A) Voc (V)
0 35.7
0.2 189.9
0.3 297.3
0.4 340.5
0.5 381.0
0.6 404.7
0.7 423.5
0.8 437.0
0.9 448.0
0.98 456.5

3. b. Short circuit test:
If(A) Isc (A)
0 0
0.08 1
0.14 1.4
0.18 2.0
0.24 2.5
0.28 3.0
0.32 3.5
0.38 4
0.42 4.5

4. At rated voltage i.e 415 V, Ie=0.7A and extrapolating the sc charactersitics, Isc at
that current is 7.6A. Hence X1=54 ohm.
Determination of X2:
Method I (by varying the 3-phase variac)
V2(l-l)(V) I2(A)
32.5 2.0
40.1 2.5
47.0 3.0
57.0 3.5
63.5 4.0
Near rated current (4 A), V=63.5 V
X2= 15.87 ohm
Method II
Voc(V) Isc(A)
72.9 4.2
77 4.5
68.1 4
60.2 3.5

5. Near rated current (4.2 A), V=72.9 V
X2= 17.35 ohm
Average=16.61 ohm
Determination of X0:
The apparatus was malfunctioning when we connected it to determine X0. With no
power/voltage supplied, a voltage of 220V existed between motor terminals, which is
weird and hence we could not do this experiment.
Results:
X1=54 ohm
X2=16.61 ohm
X0 could not be determined since the apparatus was malfunctioning