4. Turn the vernier throttle knob until both units are operating at approximately the same frequency as indicated by the
slow change in the brilliancy of the synchronizing lamps.
5. When the synchronizing lamps glow and then go out at a very slow rate, time the dark interval. Then, in the middle
of this interval, turn the circuit breaker control to the on position. This places the incoming generator set on the line, with
no load. The proper share of the existing load must now be placed on this generator.
6. The division of the kilowatt load between the alternating current generators operating in parallel depends on the
power supplied by the engines to the generators as controlled by the engine governors and is practically independent of
the generator excitation. Divide the kilowatt load between the generators by turning the vernier throttle knob
counterclockwise on the incoming generator and clockwise on the generator that has been carrying the load (to keep the
frequency of the generators constant) until both ammeters read the same, indicating that each generator is carrying its
proper percentage of the total K.W. load.
7. The division of the reactive KVA load depends on the generator excitation as controlled by the voltage regulator.
Divide the reactive load between the generators by turning the voltage regulator rheostat control on the incoming
generator (generally clockwise to raise the voltage) until the ammeters read the same on both generator sets and the
sum of the readings is minimum.
NOTE: The generator sets are equipped with a resistor and current transformer connected in series with the voltage
coil of the regulator (cross-current compensation) which equalizes most but not all of the reactive KVA load between
8. When the load is 80 per cent power factor lagging.(motor and a few lights only), turn the vernier throttle knob on the
incoming generator until the ammeter on that unit reads approximately 40 per cent of the total current load.
9. Rotate the voltage regulator rheostat control on the incoming generator clockwise to raise the voltage until the
ammeters read the same on both units.
NOTE: If a load was not added during paralleling, the total of the two ammeter readings should be the same as the
reading before paralleling. Readjust the voltage regulator rheostat on the incoming generator, if necessary.
10. To reset the load voltage, turn the voltage regulator rheostat controls slowly on each unit. It is necessary to turn the
controls the same amount and in the same direction to keep the reactive current equally divided. Power generator sets
with different capacities can also be paralleled by dividing the load proportionately to their capacity.
The procedure for stopping a power generator set or taking it out of parallel is as follows:
1. Turn off all of the load on the generator when stopping a single engine unit.
2. Shift the load from the generator when taking it out of parallel operation by turning the vernier throttle knob until the
ammeter reads approximately zero.
3. Place the circuit breaker control in the off position.
4. Turn the voltage regulator rheostat control in a counterclockwise direction to the limit of its travel.
5. Press the throttle button and turn the throttle control to stop to shut-down the engine.
NOTE: When performing a tune-up on a generator set that will be operated in parallel with another unit, adjust the
speed droop as specified in Engine Tune-Up.
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