UNDERSTANDING UPS OPERATION
Eaton
Power Xpert 9395P-600 (380V-600V) UPS Installation and Operation Manual
S
P-164000710 Rev 1
www.eaton.com/powerquality
6-6
Static
Switch
K5
Rectifier
Inverter
K1
K3
Battery
Converter
Battery
Battery
Breaker
Main Power Flow
Trickle Current
Energized
De-Energized
Closed
Open
Breakers
Contactors
K2
Bypass Input
Rectifier
Input
Output
Input
Breaker
(CB1
NOTE
On a UPS configured as an IOM, the bypass input, static switch, bypass breaker (CB4), and K5 are not present.
NOTE
On a UPS configured with a Continuous Static Switch (CSS), bypass breaker (CB4) is not present.
Figure 6‐3. Path of Current Through the UPS in Bypass Mode
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 ten minute period). The fourth transfer locks the
critical load to the bypass source and requires operator intervention to transfer.
6.2.6
Battery Mode
The UPS automatically transfers to Battery mode 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 6‐4 shows the path of electrical power through the UPS system when
operating in Battery mode.
During a utility power failure, the rectifier no longer has an AC utility source from
which to supply the DC output current required to support the inverter. The input
contactor K1 opens and the battery instantaneously supplies energy to the battery
converter. The converter boosts the voltage so that the inverter can support the
customer's load without interruption. If bypass is common with the rectifier input, the
backfeed protection contactor K5 also opens. The opening of contactors K1 and K5
prevent system voltages from bleeding backwards through the static switch and
rectifier snubber components and re-entering the input source.
