Operation
Liebert
®
eXM
™
56
Normal Mode
Operating in normal mode, the Liebert eXM’s rectifier derives power from a utility AC source and
supplies regulated DC power to the inverter, which regenerates precise AC power to supply the
connected equipment. The rectifier also uses the utility source power to charge the batteries.
Battery Mode—Requires Optional External Battery Cabinet
When utility AC power fails, the Liebert eXM protects the critical load by instantaneously channeling
battery power from optional External Battery Cabinets to the inverter, which continues supporting
the critical load without interruption. When utility power returns and is within acceptable limits, the
Liebert eXM automatically shifts back to Normal mode, with the rectifier powering the critical load.
Auto-Restart Mode
The battery may become exhausted following an extended AC utility failure. The inverter shuts down
when the battery reaches the End of Discharge voltage (EOD). The UPS may be programmed to “Auto
Recovery after EOD” after a delay time if the AC utility recovers. This mode and any delay time may
be programmed by the commissioning engineer.
Bypass Mode
When the Liebert eXM is in bypass mode, the load is directly supported by utility power and is
without battery backup protection.
The Liebert eXM’s static transfer switch will shift the load from the inverter to bypass mode without
interruption in AC power if the inverter is synchronous with the bypass and any of the following occurs:
• inverter fails
• inverter overload capacity is exceeded
• inverter is manually turned off by user
ECO Mode
When ECO Mode is enabled, the Liebert eXM switches inverter power from the UPS input to the
bypass input to save energy by improving UPS efficiency. In this mode, the bypass is the preferred
source. If the bypass voltage or frequency becomes outside preset limits, the UPS load is transferred
back to the inverter.
Battery Start Mode
The battery start option permits starting the Liebert eXM with power supplied only by the batteries
(at charged condition).
Maintenance Mode
For maintenance or repair, the Liebert eXM may be operated in maintenance mode. To place the
Liebert eXM in maintenance mode, follow the instructions in 7.4 - Switching the UPS from
Normal Operation to Maintenance Bypass.
NOTE
This unit refers to some modes and conditions that are set or adjusted using proprietary service
software. To take advantage of all the available features for the Liebert eXM, the unit must be
commissioned by an Emerson-authorized engineer.
NOTE
If the inverter is asynchronous with the bypass, the static switch will transfer the load from the
inverter to the bypass WITH interruption in AC power to the critical load. This interruption
will be less than 15ms (in 50Hz), or less than 13.33ms (in 60Hz). This interruption time may be
altered by modifying the Output transfer interrupt time setting.
WARNING
Risk of arc flash and electric shock. Can cause equipment damage, injury and death
The UPS input and output must be protected with external overcurrent protection devices. In
maintenance mode, the input and output busbars remain energized and present an electric
shock hazard.
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