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General System Information
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1.2 General System Description
The Liebert FS is a flywheel energy storage system, a mechanical battery that stores energy in the
form of a rotating mass. This energy is immediately convertible to useful electric power.
The Liebert FS is available with a wide performance range up to 190 kW as a single unit configura-
tion.
Figure 1 Liebert FS
The Liebert FS is configured as a two-terminal plus ground DC flywheel power system and is used as
a functional replacement for or an availability supplement to a bank of chemical batteries for an
Uninterruptible Power System. Like a chemical battery bank, Liebert FS receives charge and float
power from the two terminal UPS DC bus and returns power to the same DC bus whenever the bus
voltage droops below a programmable threshold level.
Integrated into a UPS, the Liebert FS is used as the alternate source of power to supply DC power to
the UPS inverter if the AC supply voltage (UPS input) is outside the acceptable range. The Liebert FS
supplies power to the UPS inverter until the utility power is restored, until an alternate power source
is available, or until the Liebert FS’ energy is exhausted.
One or more Liebert FS units may be integrated into UPS and can be put in parallel as shown in
Figures 2 and 3, to achieve higher power output or higher ride-through duration.