Operation
2.4.2Input Power Failure—Load on DC Source
If the utility AC power source fails or is outside the acceptable range, the DC source 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 DC source voltage compared to the shutdown value. The time the DC source can sustain the load depends on the size of the load and the size and condition of the DC source.
The battery block in the UPS module Monitor/Mimic Display indicates Charge or Discharge and the current in amperes.
Figure 16 Input power fail, load on DC source
Module Bypass |
|
AC Input |
|
| BFB |
Module Rectifier | DC |
AC Input | |
| Bus |
UPS Module
|
|
| UPS Output |
| Critical |
|
|
|
| ||
|
|
|
|
| Load |
To DC Supply
2.4.3Off DC Source
The DC source can be disconnected from the UPS, if required for maintenance, by opening the module battery disconnect (MBD) circuit breaker. In this situation, the UPS module will continue to supply conditioned power to the critical load, but if input power fails, the UPS system cannot supply power to the load.
NOTICE
Risk of unexpected power loss to the connected load. Can cause equipment damage.
When the UPS is operating with the module battery disconnect (MBD) circuit breaker(s) open, the critical load is not protected from loss of the utility source power.
Figure 17 Load on UPS, DC source not available
Module Bypass |
|
AC Input |
|
| BFB |
Module Rectifier | DC |
AC Input | |
| Bus |
UPS Module
UPS Output Critical
Load
To DC Supply
Liebert®NX™ | 16 |
