UNDERSTANDING UPS OPERATION
7.1.1Normal Mode
In Normal mode, utility AC power is supplied to the rectifier. The rectifier supplies DC power to the inverter, which then supplies the critical load with AC power. The rectifier also provides charging power to the battery. The battery charge condition is monitored by the UPS and reported by a status indicator on the control panel. The message System Normal appears in the status area of the control panel LCD screen.
Figure 7‐2 shows the path of electrical power through the UPS system when the UPS is operating in Normal mode.
CB4
(open)
Bypass
Static Switch
FBP
Bypass |
|
Input | (closed) |
|
Rectifier | Inverter |
| DC |
CB1 | Link |
Rectifier |
|
Input |
|
(closed) |
|
Input | Output |
Transformer | Transformer |
CB3 | Output |
(closed) |
|
CB2
(closed)
Path of Electrical Power
Battery
Figure 7‐2. Path of Current Through the UPS in Normal Mode
If the utility AC power is interrupted or is out of specification, the UPS automatically switches to Battery mode to support the critical load with no interruption. When utility power returns, the UPS returns to Normal mode.
If the UPS becomes overloaded or unavailable, the UPS switches to Bypass mode. The UPS automatically returns to Normal mode when the error condition is cleared and system operation is restored within specified limits.
If the UPS suffers an internal failure, it switches automatically to Bypass mode and remains in that mode until the failure is corrected and the UPS is back in service.
EATON Powerware® 9315 UPS |
