Emerson Liebert NX 480V - Manual (Page 63)

Operation
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Maintenance Mode
For maintenance or repair, the Liebert NX may be operated in maintenance mode. To place the Lie-
bert NX in maintenance mode, the load must be transferred to bypass and the inverter must be
turned off. When those conditions are met, the CB3 may be turned on and the UPS may be shut down,
permitting disconnecting the batteries for maintenance.
Parallel Redundancy Mode (System Expansion)
For higher capacity, higher reliability or both, the outputs of up to four UPS modules can be pro-
grammed for directly paralleling while a built-in parallel controller in each UPS ensures automatic
load-sharing.
Frequency Converter Mode
The Liebert NX can be programmed into frequency converter mode for either 50Hz or 60Hz stable
output frequency. The input frequency may vary from 57Hz to 66Hz. In this mode, the static bypass
operation is disabled and the battery becomes optional, depending on any requirement to operate in
battery mode (stored energy mode).
!
CAUTION
The internal maintenance bypass must not be used when the UPS system is in a parallel
system.
!
WARNING
The UPS input and output must be protected with external overcurrent protection devices. In
maintenance mode, the input and output busbars remain energized.