Understanding UPS Operation
7.3.4 Battery Mode – Parallel
The UPMs transfer to Battery mode automatically if a utility power outage occurs, or if the utility power does not conform to specified parameters. In Battery mode, the battery provides emergency DC power that the inverter converts to AC power.
Figure 7-7 shows the path of electrical power through the parallel system when operating in Battery mode.
Bypass Input | UPM Input |
| UPM 1 |
Battery |
|
| UPM 2 |
Battery |
|
| UPM 3 |
Battery |
|
UPM 4
Battery
Breakers
Closed
Main Power Flow
Open
Module Tie Cabinet |
UPM 1 Output |
UPM 2 Output |
UPM 3 Output |
UPM 4 Output |
Output to
Critical
Load
Figure 7-7. Path of Current through the UPMs in Battery Mode – Parallel
While in Battery mode, the UPMs sound an audible horn, illuminate a visual indicator lamp on the front panel (System Normal, On Battery), and create an entry into the alarm event history. As the battery discharges, the boost converter and inverter constantly make minute adjustments maintaining a steady output. The UPMs remain in this operating mode until the input power to the rectifier is again within the specified voltage or frequency acceptance windows.
