Powerware 5075 kVA - Manual (Page 49)

41 Powerware BPIII Harsh Environment UPS 50--75 kVA Installation and Operatio n
164201261 Rev. F 111503
Normal 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 through a DC to DC voltage
converter. The battery charge condition is monitored by the UPS and reported by a
status indicator on the Monitor Panel. The message “System Normal” appears in
the status area of the LCD screen.
Figure 18 shows the path of electrical power through the UPS system when the UPS
is operating in Normal mode.
Bypass
Rectifier
K4
Input
Input
K3 CB1
(closed)
BATTERY
Path of electrical power
RECTIFIER INVERTER
Output
TRANSFORMER
BYPASS
DC/DC
CONVERTER
CB2
(closed)
(MBP)
(open)
Input
Isolation
Transformer
(BIB)
(closed)
(MIS)
(closed)
OUTPUT
Figure 18. 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 system becomes overloaded, 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.