Tyco Electronics Galaxy SC Controller J85501F-1
Issue 13 February 2001 Glossary Appendix G - 3
since attention is required in a limited time, BD is considered a Power
Major alarm, by default.
It should be noted here that a BD alarm does not necessarily indicate that
rectifier output current has been lost or reduced. A BD alarm can be
caused by mis-adjusted rectifier output voltage during otherwise normal
operation. It can also be caused by current overload on normally
functioning rectifiers.
A BD alarm will turn on all rectifiers turned off by the energy
management algorithm, as well as rectifiers temporarily held off, after
loss of one phase of the AC.
Since the plant voltage is different in float and boost or BTP modes,
there are two thresholds for BD. One user configurable threshold for
float mode, and one user configurable threshold for boost or BTP mode.
The BD threshold for each mode is typically at least 1 volt below the
plant voltage set point for nominal 48 volt plants, or 0.5 volts below the
plant voltage set point for 24 volt plants. This threshold should be
adjusted to avoid nuisance alarms due to component tolerances,
variations in load, and other transient conditions.
In plants that have Slope Thermal Compensation enabled, special
attention must be paid to the setting to avoid nuisance alarms. STC
decreases the plant voltage at maximum 0. 1 volts for each cell in the
battery string. The BD setting should be below the maximum the plant
voltage will decrease to. For example, in a 48V plant with 24 cells the
maximum change will be (0.1 x 24) = 2.4 volts. Subtracting 2.4 from the
nominal plant voltage of 54.50 volts = 52.1V. The BD level should be
set below 52.1 volts.
Very Low
Voltage
If the battery reserve has almost ended, and the plant voltage has
dropped to a point where the equipment will soon cease to operate or be
damaged, the controller will create the very low voltage alarm (VLV) to
warn of the impending equipment loss. Some form of corrective action
is imperative.
VLV is considered a Power Critical alarm, by default.
The VLV alarm threshold setting should be near the end of the battery
discharge, where operator intervention or notification is required. Refer
to the equipment and battery product manuals for an appropriate
threshold.
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