Eaton Power Xpert 9395P 250 kVA, User And Installation Manual

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64 9395P 250 kVA / 275 kVA / 300 kVA
User’s and Installation Guide
6.2.3 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 directly. Figure 6-3 shows the path of
electrical power through the UPS system when operating in Bypass mode.
CAUTION
The critical load is not protected while the UPS is in Bypass mode.
Figure 6-3. Path of current through the UPS in bypass mode
NOTE
On a UPS configured as an IOM, the bypass input, static switch, and K5 are not present.
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 transient 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 solid-state, silicon-controlled rectifier (SCR) static switch (SSW)
and a backfeed protection contactor K5. The static switch is rated as a continuous-duty device that is
used anytime the inverter is unable to support the applied load. The static switch is wired in series with
the backfeed protection contactor, and together they are wired in parallel with the rectifier and inverter.
The static switch, being an electronically-controlled device, can be turned on immediately to pick up the
load from the inverter while the inverter output contactor K3 opens to isolate the inverter. The backfeed
protection contactor is normally always closed, ready to support the static switch unless the bypass
input source becomes unavailable.
(Optional)