Emerson 115-120 Manuel D’Utilisation

The UPS is designed to operate as an on-line, double-conversion, reverse-transfer system in the 

following modes:

• Normal  Mode
• Battery  Mode
• Auto-Restart Mode
• Bypass Mode
• Battery Start Mode
• Maintenance Mode (Manual Bypass)
• Sleep  Mode
• Paralleling Mode

Operating in normal mode, the Liebert

®

 APM

™

’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.

When utility AC power fails, the Liebert APM protects the critical load by instantaneously channeling 

battery power to the inverter which continues supporting the critical load without interruption. When 

utility power returns and is within acceptable limits, the Liebert APM automatically shifts back to 

Normal mode, with the rectifier powering the critical load.

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.

When the Liebert APM is in bypass mode, the load is directly supported by utility power and is 

without battery backup protection.
The Liebert APM’s static transfer switch will shift the load from the inverter to bypass mode without 

an 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 

The battery start option permits starting the Liebert APM with power supplied only by the batteries 

(at charged condition).

NOTE
If the inverter is asynchronous with the bypass, the static switch will transfer the load from the