UNDERSTANDING UPS OPERATION
Eaton
Power Xpert 9395P UPS (300 kVA, 300 kW) Installation and Operation Manual
S
P-164000563 Rev 1
www.eaton.com/powerquality
6-5
VMMS's UPM automatic scheduling rotates the idle UPMs every month with the
ABM cycle. This allows the UPMs to have equal load-share time and also conducts a
periodic UPM readiness test. The automatic ABM scheduler selects the next UPM in
turn after each charge-to-float transition. If ABM is disabled, the scheduler selects the
next UPM after conducting the automatic battery test. If ABM and automatic battery
tests are disabled, the scheduler selects the next UPM at the beginning of each
month.
In High Alert mode, the UPS defaults to double-conversion Online mode and all UPMs
go active for one hour (customer configurable). At the completion of the hour, the
UPS defaults back to VMMS mode. If the High Alert command is received during the
one hour, the one hour timer will be restarted.
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.
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The critical load is not protected from voltage or frequency fluctuations or power outages while the UPS is in
Bypass mode.
MISE EN GARDE!
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.
