GE Industrial Solutions Galaxy Pulsar Edge - Manual (Page 177)

Galaxy Pulsar Edge Power System Controller
Issue 3 October 2011
177
This feature may be used by customers to determine if the load being served is greater than N
rectifiers worth, in an N+1 system. That is, the load requirements have changed such that the
power system is no longer operating as a redundant power system. An additional rectifier may be
required to ensure continuous redundant operation. More rectifiers may be required if more than
N+1 redundancy is configured and required.
If enabled, this feature will be disabled during battery discharge and recharge conditions. It will
be enabled when the battery charging current falls below 5A.
Battery Voltage Imbalance Detection
This feature requires the use of the ES771A Remote Voltage Monitoring Module. Note that this
feature is automatically enabled if the controller detects the presence of the ES771A module. This
module is to be placed in the electronics cabinet and utilizes the QS873A VT-Probes to measure
the mid-string voltage of the particular battery string being monitored. The VT-Probe is to be
placed on the negative battery terminal of the battery located in the middle of the battery string.
The Pulsar Edge controller has data on the system DC bus voltage. The half-string voltage
measurement obtained from the ES771 monitoring the battery string is compared to the system
DC bus voltage minus the value of the half-string voltage measurement. If the comparison results
in a difference of greater than 1.7V or the value configured for this threshold for longer than 12
hours, the alarm is asserted. The alarm may be retired by initiating the Clear Events command.
After this feature has been enabled, the system waits for 12 hours to ensure the battery strings are
stable. A battery string is considered to be stable if the charging current is less than 3A. If a stable
battery string yields a difference measurement greater than 1.7V or the value configured for this
threshold for over 12 continuous hours, a Battery Voltage Imbalance alarm is generated.
When the alarm is issued, the Float Set-Point (fsp) and the Battery On Discharge (BD) threshold
values are reduced by fsp/Number of Cells per string. Thus, for an fsp=54.5 the system DC bus
voltage would be reduced by 54.5/24 or approximately 2.27V. Once the alarm has been cleared
by the Clear Events (CLE) command, the plant reverts to its normal fsp; however, the BD
threshold is maintained at the new threshold for up to four minutes before reverting back to the
old threshold. This is done to ensure the batteries have had enough time to charge up to the
nominal fsp and to prevent any spurious BD alarm conditions.
This feature may be used by customers as part of their overall battery maintenance program in
determining the health of battery strings. A voltage imbalance of 1.7V or the value configured for
this threshold between half-string voltages may mean a shorted-cell exists somewhere in the
string. A service person can be sent out to the site and determine if the string is bad and should be
replaced.
Battery Recharge Current Limit
The battery recharge current limit feature enables the Pulsar Edge controller to limit the recharge
current flowing into a battery section during the charge cycle. The recharge current flowing into
the battery section can be limited to any value between 5A and 1000A.
Note that this feature will not have any impact on the current being delivered to the load. Further,
there will be no effect on the discharge current flowing from the battery strings to the load during
an ac fail condition. The controller will try and maintain the recharge current to within 10% of the
set level.