Lucent Technologies Lineage
®
2000 ECS-6U Controller J85501E-1
2 - 8 Product Description
Issue 4 August 1998
the external alarm system. HV is considered a Major alarm, so
all Power Major alarm groups are also issued.
When reporting the alarm, the controller sends a simultaneous
shutdown signal to all rectifiers. Since the outputs of all rectifiers
are paralleled in the plant, their output voltages are forced to be
the same. Their output currents, however, may vary widely. In a
high voltage condition caused by an individual rectifier failure,
the failed rectifier will be supplying more current than any other
rectifier. When the high voltage shutdown signal is sent by the
controller, the rectifier supplying the most current, i.e., the failed
rectifier, will shut down, causing the plant voltage to drop to
normal and the HV alarm to retire. All other rectifiers will
remain on. If a high voltage condition exists without an
individual rectifier failure, e.g., because of incorrect setting of
the HV-threshold DIP switches or lightning-induced high
voltage, the rectifier with the highest output current will shut
down, but the HV condition will remain. The rectifier with the
highest output current of those remaining on will shut down
next, but again the HV condition will remain. This will continue
until all rectifiers have shut down. Note that although it is a
sequential shutdown of rectifiers, the timing is very fast, and it
will appear as if all rectifiers have shut down simultaneously.
The detection of the high voltage condition and sending of the
shutdown signal are functions of the controller, while the
selection of the rectifier with the highest output current for
shutdown is a function of the rectifiers.
If the rectifiers have load sharing, the HV shutdown operates
differently. In this case, if a single rectifier fails, its output
current will try to increase and the HV signal will shut down
only that rectifier. If the entire bus goes high, the rectifiers will
still share current equally and no shutdown will occur unless the
bus voltage reaches the backup high voltage shutdown.
CAUTION
Do not use the load share option for a single rectifier.
The high voltage shutdown threshold voltage should be set by
the user to a prescribed margin above the plant float voltage.
(See Section 4, “High Voltage Shutdown Thresholds.”) This
margin is typically 1.0 volts for nominal 48V battery plants and
0.5 volts for nominal 24V battery plants. Since voltage
fluctuations are greater in batteryless plants, the shutdown
margin is typically set at 3 volts above float in 48V batteryless
plants or 1.5 volts for 24V batteryless plants. The actual
threshold voltage is set with a group of DIP switches on the