Prior to commissioning ensure that all measuring devices are connected in correct phase sequence. The connect command for the unit circuit breaker must bedisconnected at the unit circuit breaker. The field rotation must be monitored for proper rotation. Any absence of or incorrect connection of voltage measuring devices or other signals may lead to malfunctions and damage the unit, the engine, and/or components connected to the unit
Synchronizing the Generator
The phase detector compares the two signals and determines any difference
between the generator and bus phases. When there is a difference, the speed
bias circuit sends a correction signal to the Load Sharing and Speed Control. The
correction signal increases or decreases engine speed depending on whether
the generator is lagging or leading the bus. Correction signal amplitude is
proportional to the amount of lead or lag (phase difference).
The phase window, dwell time, and breaker close circuit receive inputs from the
phase detector. Using signals derived from the generator and bus inputs, the
phase window circuit checks the phase angle. When the phase angle is less than
the selected angle (inside the window) the dwell time circuit begins to measure
the amount of time (dwell) the input signals are in phase and makes sure the
signals remain in phase during breaker closure. When phase angle and dwell
time requirements are correct, the breaker closing circuit sends a signal to the
relay driver/inhibitor. The enable circuit gives a secondary relative phase angle
check and turns on an indicator. When both the breaker closure circuit and
enable circuit say the conditions have been satisfied, a signal is sent to the
breaker closure relay. Then the breaker changes state for about one second.
Connections for normally open contacts are provided.
The synchronizer, with or without voltage matching, will not close the circuit
breaker connecting the generator to a dead bus. If there is no voltage to the bus
then no correction signal is sent to the Load Sharing and Speed Control and no
breaker closure signal is sent to the breaker.
If a dead-bus relay is used to close the breaker, the synchronizer mode switch
must be in the OFF position until the synchronizer is required to synchronize and
close the breaker to a live bus.
Voltage Matching
The voltage comparator circuit compares the generator and bus voltages. If there
is a difference, the circuits issue appropriate raise or lower commands to the
voltage regulator through relay contacts (see Figures 1-3 and 1-4). A voltage
offset potentiometer (factory set with identical bus and generator inputs) is
included in the voltage matching circuit to compensate for internal circuit
differences. This voltage offset should be readjusted only when the bus and
generator are paralleled.
The voltage comparator circuit also provides input to the relay driver/inhibitor.
Any voltage difference between the generator and bus must be within the
selected voltage range before the close breaker command may be given.
The voltage matching circuit is disabled when the breaker closure signal is
issued.
