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5.3.6 DISCHARGE Mode
Starting from either CHARGE or READY mode, the Liebert FS will enter the DISCHARGE mode if
the UPS DC Bus Voltage goes below Vcharge. In DISCHARGE mode, the Liebert FS will regulate the
DC bus at Vreg.
Figure 50 DISCHARGE mode diagram
The Liebert FS will be in DISCHARGE mode as long as:
• UPS DC Bus Voltage < Vcharge and
• Liebert FS’s SOC is more than 0%.
The Liebert FS will leave the DISCHARGE mode and transition into CHARGE mode if the UPS DC
bus recovers (UPS DC Bus Voltage = Vcharge) before the Liebert FS’s SOC reaches 0%. In case the
UPS DC bus doesn’t recover before the Liebert FS’s SOC reaches 0%, the Liebert FS will transition
into SHUTDOWN mode.
5.3.7 SHUTDOWN Mode
In SHUTDOWN mode, the flywheel will actively spin down.
There are two ways the Liebert FS can transition into SHUTDOWN mode, by a complete discharge
and by a user command.
Following a Liebert FS Discharge Down to SOC = 0%
This is the most common SHUTDOWN process. This occurs when the Liebert FS’s SOC drops below
0% and the UPS System DC Bus voltage is less than Vcharge. If the Liebert FS entered the SHUT-
DOWN mode after leaving DISCHARGE mode, the Liebert FS will automatically transition into
STARTUP mode provided the UPS System DC Bus voltage returns to a value greater than Vcharge
(i.e., when the electric grid returns or the standby generator supplies power to the UPS).
Figure 51 SHUTDOWN mode diagram - shutdown after full discharge
State of Charge < 0 State of Charge > 0
0%
1
00%
99.5%
Note: UPS DC Bus Voltage = Vreg
State of Charge < 0 State of Charge > 0
0%
1
00%
99.5%
Note: UPS DC Bus Voltage < Vcharge
DISCONTINUED
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