8
SALICRU
4.3.3. Bypass Mode
If the inverter overload capacity is exceeded under Normal mode,
or if the inverter becomes unavailable for any reason, the static
transfer switch will perform a transfer of the load from the inverter
to the bypass source, with no interruption in power to the critical
AC load. Should the inverter be asynchronous with the bypass, the
static switch will perform a transfer of the load from the inverter
to the bypass with power interruption to the load. This is to avoid
large cross currents due to the paralleling of unsynchronized AC
sources. This interruption is programmable but typically set to be
less than 3/4 of an electrical cycle, e.g., less than 15ms (50Hz) or
less than 12.5ms (60Hz). The action of transfer/re-transfer can also
be done by the command through monitor.
Rectifier
AC/DC
Main
Static Bypass
Manual Bypass
Inverter
DC/AC
Charger
DC/DC
Output
Battery
Bypass
Fig. 5.
Bypass mode operation diagram
4.3.4. Maintenance Mode (Manual Bypass)
A manual bypass switch is available to ensure continuity of supply
to the critical load when the UPS becomes unavailable e.g. during
a maintenance procedure. (See Fig. 6).
Rectifier
AC/DC
Main
Static Bypass
Manual Bypass
Inverter
DC/AC
Charger
DC/DC
Output
Battery
Bypass
Fig. 6.
Maintenance mode operation diagram
Danger:
During Maintenance mode, dangerous voltages are present on
the terminal of input, output and neutral, even with all the mo-
dules and the LCD turned off.
4.3.5. ECO Mode
To improve system efficiency, UPS rack system works in Bypass
mode at normal time, and inverter is standby. When the uti-
lity fails, the UPS transfers to Battery Mode and the inverter
powers the loads.
Rectifier
AC/DC
Main
Static Bypass
Manual Bypass
Inverter
DC/AC
Charger
DC/DC
Output
Battery
Bypass
Fig. 7.
ECO Mode operation diagram
Note:
There is a short interruption time (less than 10ms) when
transfer from ECO mode to battery mode, it must be sure that
the interruption has no effect on loads.
4.3.6. Auto-restart Mode
The battery may become exhausted following an extended
AC mains failure. The inverter shuts down when the battery
reaches the End of Discharge Voltage (EOD). The UPS may
be programmed to “System Auto Start Mode after EOD”. The
system starts after a delay time when the AC mains recovers.
The mode and the delay time are programmed by the commis-
sioning engineer.
4.3.7. Frequency Converter Mode
By setting the UPS to Frequency Converter mode, the UPS could
present a stable output of fixed frequency (50 or 60Hz), and the
bypass static switch is not available.
4.4. UPS STRUCTURE
4.4.1. UPS Configuration
The UPS configuration is provided in Table 1
