EEP 303 lab report

1. Experiment 1 (II Cycle): Synchronization of a given alternator with infinite bus and seeing
power exchange with the grid
Aim:
- Synchronization of a given alternator with infinite bus
- Study of the effect of speed controller of prime mover on real power sharing
- Study of the effect of excitation on reactive power sharing
Basic theory:
 For complete synchronization of two 3-phase systems the following conditions
should be met:
1. Frequency of both the systems should be same
2. Voltages must be equal
3. Phase sequences of both systems should be same
 Changing its excitation cannot change the real power output of a synchronous
generator operating in parallel in a system of constant frequency and constant
voltage. As the generator speed remains same, change in excitation would change the
power factor at which the synchronous generator operates without changing the
power output.
 The output of a synchronous generator with fixed V terminal, fixed excitation and
fixed frequency may be changed by changing its governor setting (speed load
characteristic)
Equipment and components:
- Two synchronous machines coupled to D.C. shunt motors (prime movers)
- DC and AC ammeters and voltmeters
- Watt meters
- Synchronized panel with lamps
- Tachometer
- Loading and field rheostats
Circuit diagram:
1. Synchronization of the alternator with grid:

2. 2. Study of the effect of speed controller of prime mover on real power sharing
3. Study of effect of excitation on reactive power sharing:
Observations:
1. Active power flow exchange with grid:
Vterminal = 385 V
Motor armature current Alternator armature
current
Power (W)
14.4 2.7 1240
12.6 2.5 1080
11.2 2.3 1000
9.8 2.1 880
2. Reactive power exchange with grid:
Excitation current at zero power = 0.3 A (Alternator field current)
Alternator excitation
current
Alternator armature
current
Power
Over-excitation
0.76 3.95 13603
0.70 3.55 12003
0.62 2.9 9603
0.40 1.15 3603
Under excitation
0.0 2.4 8003
0.06 1.85 6003
0.10 1.45 4403
0.16 1.00 2403
Conclusion:
- As the speed of primer mover is controlled, i.e. motor field current is changed the real
power sharing of the alternator with grid is affected. More the speed, more the real
power transfer from alternator to the grid

3. - If the alternator excitation current is increased from zero-power excitation current
(Iz), more reactive power is transferred to the grid (over-excited state). If it is
decreased from Iz more and more reactive power is taken from grid and the alternator
is said to be in under-excited state