Operation

2.3.3Input Power Failure—Load on Battery

If the utility AC power source fails or is outside the acceptable range, the battery plant becomes the power source for the UPS module inverters. The UPS continues to supply power to the critical load and also to the UPS controls.

Use the Battery Time screen at the UPS modules to monitor the present battery voltage compared to the shutdown value. The time the battery can sustain the load depends on the size of the load and the size and condition of the battery plant.

Alarm messages that indicate battery status are Battery Discharge, Low Battery and Battery Shut- down. The voltage limits for these alarms are displayed on the UPS module Alarm Limit Settings screen. These limits were selected for your installation by Liebert Services during initial startup. The battery block in the UPS module Monitor/Mimic Display indicates Charge or Discharge and the cur- rent in amperes.

Figure 26 Input power fail, load on battery

Bypass

BFB

Input

DC Bus

CB1

CB2

Module Output

Battery System

MBD

21

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Emerson 250-400kVA manual Input Power Failure-Load on Battery, Input power fail, load on battery