Powerware 5075 kVA - Manual (Page 50)

42 Powerware BPIII Harsh Environment UPS 50--75 kV Installation and Operation
164291261 Rev. F 111503
Bypass Mode
The UPS automatically switches to Bypass mode if it detects an overload, load
fault, or internal failure. The bypass source supplies the commercial AC power to
the load through an internal switch and an internal transformer.
CAUTION:
The critical load is not protected while the UPS is in Bypass mode.
Figure 19 shows the path of electrical power through the UPS system when the UPS
is operating in Bypass 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 19. Path of Current Through the UPS in Bypass Mode
You can transfer the UPS from Normal mode to Bypass mode manually. However,
the UPS switches automatically to Bypass mode whenever the inverter can no
longer supply the critical load. If the UPS transfers to Bypass mode from Normal
mode due to any reason other than operator intervention, the UPS automatically
attempts to transfer back to Normal mode (up to three times within a 10-minute
period).
Bypass mode is a normal operating mode, and not an alarm condition. However, if
the UPS is unable to return to Normal mode following an automatic transfer to
Bypass mode, an alarm condition will be recorded.