Bypass Mode - Powerware 9330 Installation And Operation Manual

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.
MAINTENANCE
BYPASS SWITCH
CB1 K1
Breakers Contactors
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
6--6
BYPASS MODE
STATIC
K5
SWITCH
RECTIFIER
CHARGER
Closed
Open
BATTERY
BOOST
CONVERTER
K2
CB2
Powerware 9330 (10 kVA- -40 kVA) Installation and Operation
INVERTER
K3
MAINTENANCE
BYPASS SWITCH
Main Power Flow
Trickle Current
Energized
De- -Energized
164201300 REV. G 061502