Technical data

9
7 Electronic Static Switch
MASTERGUARD Series SIII
UPS Systems from 60 to 800 kVA
MKA4CAT0UKSIII/Rev. 11-11/2004/UK
• Uninterrupted automatic retransfer
from the reserve supply, as soon
as the inverter regains the capacity
to supply the load.
•The uninterrupted transfer from the
inverter to the reserve supply shall
be inhibited in the following
situations:
- reserve supply voltage outside
limits
-failure of electronic bypass switch.
•The uninterrupted automatic
retransfer may be inhibited in the
following situations:
- manual switching to reserve supply
via the maintenance switch
-failure in output switch behind
inverter
-UPS output overload.
7. 1 .1 Voltage
The nominal voltage of the reserve line
shall be 230/400V
RMS
. Any transfer
from inverter to reserve line will be
inhibited if the voltage is beyond a limit
of ±10% (standard setting) of the
nominal voltage.
7. 1.2 Transfer time (double conversion)
The switching time for a transfer from
the inverter to the reserve supply or
vice versa shall be less than 0.5ms
when synchronised. The system shall
ensure that the inverter is stable and
operating normally before permitting a
retransfer of the load back to inverter.
This automatic retransfer delay time
back to inverter from reserve shall be 5
seconds. The transfer time when out
of synchronisation shall be 20
milliseconds to prevent damage to the
load by phase reversal.
7. 1 .3 Overload
The electronic static switch shall be
capable of supporting the following
overloads:
125% for 10 minutes
150% for 1 minute
700% for 600 milliseconds
1000%for 100 milliseconds
7. 1 .4 Manual maintenance bypass
It shall be possible to implement a
manual uninterrupted bypass of the
complete system in order to enable
maintenance work to be carried out on
the system. The reserve supply will
continue to feed the load. In this case
the UPS will be voltage-free as it will
be disconnected from the supply
networks. In this case, maintenance
work on the UPS can be carried out
without affecting the connected
electric load.
7.1 General
The electronic static switch shall be a
fully rated, high speed, solid-state
transfer device and rated for
continuous duty operation. Each AC
phase of the input shall be individually
fitted with fast acting fuses to prevent
cascading failures.
The following transfer and retransfer
operations shall be provided by the
electronic static switch:
• Uninterrupted automatic transfer to
the reserve supply in the event of:
-inverter output overload
- DC voltage outside limits
-over-temperature
-inverter failure
• If inverter and reserve supply are
not synchronised at the time of a
necessary transfer, a switching
delay can be set to protect the
critical load. This prevents possible
damage to the load by
unintentional phase shift. A delay
of 20ms will be preset as a
standard value.
• Uninterrupted manual transfer/
retransfer to and from the reserve
supply shall be initiated from the
control panel.
• Uninterrupted automatic transfer/
retransfer to and from the reserve
supply by activation of the line
interactive mode.
Tecnico-SIII-MG 10-11-2004 8:22 Pagina 9