2: General Description
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TS_616_08 PW8000DPA ST (S2) User Manual 21/4/22
In a parallel-module installation (i.e. where two or more UPS modules fitted to the frame) the inverter control logic also
ensures balanced load sharing between the on-line modules together with inter-module frequency synchronisation.
Static switch
The static switch provides a means of connecting the UPS AC output directly to the unregulated bypass mains supply.
Working in conjunction with the inverter and output relay, the static switch control logic is able to transfer the UPS AC
output (load) between the inverter and bypass supply without a break in the load supply. Load transfer between the
inverter and bypass can be selected manually from the operator control panel and takes place automatically following a
UPS fault that prevents the inverter from providing its correct output (including temporary overload situations).
Note: A brief load break will occur when transferring from bypass to inverter following a bypass supply failure, or if the
bypass/inverter are not synchronised when a transfer is demanded. (See ‘Off Line Mode’ in section 2.3.3).
Automatic battery changeover switch
If the UPS mains input supply fails, or undergoes a sustained dip (brownout), the automatic battery switch will close to
connect the battery to the DC boost converter input. This enables the inverter to continue its normal operation and
maintain the UPS output load supply from battery power.
2.3.2 UPS module operational states
Under normal circumstances the UPS module will operate in one of three states: On Inverter, On Battery or ON Bypass –
these are described below.
UPS ON-INVERTER mode
Figure 2.4 illustrates the UPS
ON-INVERTER
mode, which is usually considered the ‘normal’ mode of operation:
• The input relay is closed.
• The rectifier and DC boost converter are turned on to supply controlled DC power to the inverter input.
• The battery charger is operational and provides controlled battery charging.
• The inverter is operational and provides an AC output.
• The output relay is closed to connect the inverter output to the UPS AC output terminals to provide the load with
processed power.
• The static switch is off.
Figure 2.4 UPS ON-INVERTER
AC/DC (PFC)
CONVERTER
DC BOOST
CONVERTER
DC/AC
INVERTER
BATT. CHARGER
STATIC
SWITCH
UPS AC
Output
UPS
Bypass
Mains
UPS
Input
Mains
BATTERY
UPS MODULE
Input
Relay
Automatic
Batt. Switch
Output
Relay