Powerware 9330 - Manual (Page 80)

6--6 Powerware 9330 (10 kVA--40 kVA) Installation and Operation
164201300 REV. G 061502
6.2.2 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.
CB1
CB2
K1
K5
K3
K2
Open
Closed
Breakers Contactors
Main Power Flow
Energized
De--Energized
Trickle Current
RECTIFIER
BOOST
CONVERTER
INVERTER
BYPASS MODE
CHARGER
BATTERY
STATIC
SWITCH
MAINTENANCE
BYPASS SWITCH
MAINTENANCE
BYPASS SWITCH
Figure 6---3. Path of Current Through the UPS 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 solid state silicon controlled rectifier (SCR)
static switch (SSW), and a back feed protection contactor (K5). The static switch is
rated as a continuous duty device that is used anytime the boost converter and
inverter is unable to support the applied load. The static switch is wired in series
with the back feed protection contactor and together they are wired in parallel with