Bypass Mode - Eaton Power Xpert 9395P-900 Series Installation And Operation Manual

6.2.5

Bypass Mode

NOTE Bypass mode is not available on a UPS configured as an IOM.
The UPS automatically switches to Bypass mode if it detects an overload, load fault, or internal failure. The UPS
can also be transferred from Normal mode to Bypass mode manually. The bypass source supplies the
commercial AC power to the load directly. Figure 6-3 shows the path of electrical power through the UPS
system when operating in Bypass mode.
In Bypass mode, the output of the system is provided with three-phase AC power directly from the system
input. While in this mode, the output of the system is not protected from voltage or frequency fluctuations or
power outages from the source. Some power line filtering and spike protection is provided to the load but no
active power conditioning or battery support is available to the output of the system in the Bypass mode of
operation.
The internal bypass is comprised of a SCR continuous static switch, and a backfeed protection contactor K5.
The static switch is used instantaneously anytime the inverter is unable to support the applied load. The
continuous static switch is wired in series with the backfeed protection contactor, and together they are wired
in parallel with the rectifier and inverter.
The critical load is not protected from voltage or frequency fluctuations or power outages while
the UPS is in Bypass mode.
Les charges critiques ne sont pas protégées des fluctuations de tension ou de fréquence ni des
pannes de courant lorsque l'onduleur est en mode Contournement.
The static switch, being an electronically-controlled device, can be turned on immediately to pick up the load
from the inverter while inverter output contactor K3 opens to isolate the inverter. The backfeed protection
contactor is normally closed, ready to support the static switch unless the bypass input source becomes
unavailable
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Eaton Power Xpert 9395P-900 UPS Installation and Operation Manual P-164000501—Rev 09
CAUTION
ATTENTION!
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Understanding UPS Operation
6-5