Powerware 9330 - Manual (Page 82)

6--8 Powerware 9330 (10 kVA--40 kVA) Installation and Operation
164201300 REV. G 061502
6.2.3 High Efficiency Mode
When the UPS is operating in High Efficiency mode, the bypass source supplies
the commercial AC power to the load directly.
Figure 6---4 shows the path of electrical power through the UPS system when
operating in High Efficiency mode.
CB1
CB2
K1
K5
K3
K2
Open
Closed
Breakers Contactors
Main Power Flow
Energized
De--Energized
Trickle Current
RECTIFIER
BOOST
CONVERTER
INVERTER
HIGH EFFICIENCY MODE
CHARGER
BATTERY
STATIC
SWITCH
MAINTENANCE
BYPASS SWITCH
MAINTENANCE
BYPASS SWITCH
Figure 6---4. Path of Current Through the UPS in High Efficiency Mode
In High Efficiency mode, the output of the system is provided with three phase AC
power directly from the system bypass input. 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 High Efficiency mode of
operation. However if the bypass source falls outside of a predetermined voltage
or frequency window, the system forward transfers and the inverter assumes the
load. The transfer takes place in less than 4 ms (quarter cycle), to ensure loads
being fed by the system output are not interrupted.
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. The static switch is wired in series with the back
feed protection contactor and together they are wired in parallel with the inverter.
In the High Efficiency mode, the static switch is turned on to supply the majority of
the load current directly to the load while the Inverter remains on line, ready to
assume suppling the load.
High Efficiency mode is a normal operating mode, and not an alarm condition.
While the UPS is in High Efficiency mode, the NORMAL light on the front display
will illuminate.