GE Industrial Solutions Galaxy Vector Controller GCM3 - Manual (Page 44)

Galaxy Vector Controller GCM2, GCM3
3 - 10 Operation Issue 4 January 2008
Additionally, there must be no active ac failure and rectifier
phase alarms, since the load would immediately disconnect
after reconnecting. At power up, there is an 18-second delay
before the load is reconnected to allow the rectifiers to walk
in.
Refer to the Alarm Descriptions section for alarms associated
with these two contactors (Contactor Open and Contactor Fail).
Refer to the associated plant documentation for information on
connecting these Load and Battery Disconnect driver circuits to
the BLJ3 terminal connection board or the BTJ2/BTJ3
connection board.
Thermal Compensation Features and Alarms
The Vector has a flexible Thermal Compensation feature which
provides voltage compensation from that level established by the
Plant Float Set-Point (FSP), dependent on the highest
temperature monitored by thermistors located at the plant
batteries. Thermal Compensation should only be enabled when
the controller is used in a plant containing “sealed” or valve
regulated “maintenance free” batteries. This feature requires the
use of external thermistors at the plant batteries to monitor cell
temperatures. Refer to the Installation section for more details on
wiring and configuring this feature.
Thermal Compensation lowers plant voltage from the FSP for
monitored battery temperatures which are above the ideal
temperature established during configuration as the Battery
Thermal Slope Nominal Temperature. Lowering the plant
voltage helps to keep the batteries at their optimum state of
charge while protecting them from thermal runaway. Thermal
runaway is a complex sealed battery phenomenon where, for a
number of reasons, one or more cells in a string are unable to
dissipate the internal heat generated by their charging current
and experience an increase in internal temperature. By lowering
the float voltage as cell temperature increases, the float current
is lowered to a point where this destructive behavior can be
avoided. If a cell failure is imminent and the cell temperature
continues to rise above the threshold configured for Battery
Thermal Step Temperature, the plant voltage drops in a single
step to a level which helps keep from overcharging and
damaging the remaining cells in the string. Refer to Figure 3-1
for a graphical view of Battery Thermal Compensation and the
relationship of its various set points. Figure 3-2 shows the same
information for the Flexent system.