ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
Experiment No. 3
Synchronous Generator Parameters
Objectives
The objectives of this experiment are to find the synchronous reactance (Xd) and mutual
reactance from open circuit characteristic and reactive loading of a 3- φ synchronous
generator.
Apparatus
1. 2 test tables
2. DC motor-synchronous generator set
3. 1 Ω field rheostat
4. 1 5 A Kenwood DC power supply
5. 1 0-5 A DC ammeter
6. 1 0-10 A DC ammeter
7. 1 0-150 V DC voltmeter
8. 1 current transformer
9. 1 0-5 A AC ammeter
10. 2 Wattmeters
11. 1 0-300/150 V AC voltmeter
12. Tachometer for synchronous generator
13. Strobe
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ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
Procedure
Part 1: Open Circuit Characteristic (OCC)
a) Set up the circuit shown in Fig.1. The synchronous generator should be connected for
220 V 3- φ wye operation.
b) Start the DC motor.
c) Adjust IFmotor until the speed of the dc motor-synchronous generator set, n, is at
synchronous speed; i.e., n = ns.
d) Holding the speed constant, adjust IFgen until VOC equals 140% of rated voltage.
Measure and record IFgen, VOC and n.
e) Turn off the motor-generator set.
Part 2: Reactive Loading of Synchronous Generator
a) Set up the circuit shown in Fig.2. The synchronous generator should be connected for
220 V 3- φ wye operation.
b) Keep the switches of test table 2 open. Start the DC motor.
c) Adjust IFmotor until the speed of the dc motor-synchronous generator set, n, is at
synchronous speed; i.e., n = ns.
d) Adjust IFgen until the voltage across the terminals of synchronous generator is brought
to rated value. Measure IFgen.
e) Make sure that the capacitive bank is connected to the rated voltage. Initially, set the
capacitive bank to infinity.
f) Close the switches of test table 2 and adjust the load to 20A approximately. Measure
the currents (I1, I2, and I3) and voltages (V12, V23, and V31) at the terminals of the
source.
g) Repeat part f for different load conditions. Make sure the load is balanced.
h) Turn off the motor-generator set.
Report
1. Plot the open circuit characteristic VOC versus IFgen. Draw a tangent passing through
the origin to the graph. Find the slope of the tangent and this will give you direct axis
mutual inductance Xmd.
2
n
∑
Xmd
3
⋅ VOC
i
If
i=1
i
n
2. From part 2 of the experiment, for the measured value of IFgen, find VOC from OCC.
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ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
3. Find Xd using equation
VT
Ean − Ias ⋅ra − j ⋅Iad ⋅Xd − jIaq ⋅Xq
Where Ean is the induced emf
VT is the measured terminal voltage of the synchronous machine
Xd is the direct axis reactance
Xq is the quadrature axis reactance
Ias is the stator line current in phase A.
Iad is the direct axis stator current
Iaq is the quadrature axis stator current.
3/6
ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
Tabular Form for Open Circuit Characteristic (OCC):
S.No
IFgen
V12
V23
V31
A
V
V
V
VOC
V12 + V23 + V31
3
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Tabular Form for Reactive Loading:
S.No
I1
A
I2
A
I3
A
IL
A
V12
V
V23
V
V31
V
1.
2.
3.
4.
5.
6.
7.
8.
9.
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VT
V
IFgen
A
VFgen IFmotor NS
RPM
V
A
ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
Where
ILoad
VT
I1 + I2 + I3
3
V12 + V23 + V31
3⋅ 3
NS = Synchronous speed
5/6
ECE 420
Spring 2007 – on-campus
Experiment o. 3
Synchronous Generator Parameters
TEST TABLE 1
DC MOTOR
TEST TABLE 2
AC GENERATOR
L1
A
VOC
F
L2
120 VDC
IFgen
120 VDC
Fig. 1: Circuit diagram of the laboratory setup for determining the open circuit characteristics
TEST TABLE 1
DC MOTOR
TEST TABLE 2
AC GENERATOR
L1
A
F
VOC
L2
120 VDC
IHR1
IFgen
120 VDC
Fig. 2: Circuit diagram of the laboratory setup for reactive loading.
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Inductive
Load