OMD91046 rev D
15
1.4 STATIC
SWITCH
The static switch, the diagram of which is shown in picture 6, is composed of
thyristors, rated to work continuously at 200% of nominal output power.
The components connected to the bypass line are protected by ultra-quick fuses.
The static switch is provided with a protection which minimizes the risk caused by a
possible return of the inverter voltage in case of emergency mains failure (back-feed
protection). Thanks to the transfer logic integrated in the control, the load is supplied by
the bypass line even in case of microprocessor failure. The overload capacity of the
static switch is shown below.
Overload capacity:
200% continuous
1000%
for
1
cycle
1.4.1 Inverter
Emergency Line Transfer
The transfer is activated only if the emergency line is in tolerance (in less than 0.5
ms), for the following reasons:
CAUSES
COMMUTATION CONDITIONS
Output short-circuit
Emergency line within tolerance limits
Fault of inverter or inverter voltage out of tolerance
Emergency line within tolerance limits
DC voltage out of tolerance (Inverter OFF)
Emergency line within tolerance limits
Overtemperature
Emergency line within tolerance limits
Thermal image shut down
Emergency line within tolerance limits
Forced commutation by “BYPASS SWITCH” (test or
service)
Emergency line within tolerance limits and
SYNCHRONIZED inverter
1.4.2 Emergency Line
Inverter transfer
As soon as inverter is correctly working and synchronized, UPS automatically
switches the load to inverter in less than 1 msec. If UPS switches back and forth more
than 6 times in two minutes an alarm will be generated, to inform the user, and the load
will be locked to emergency line. A manual reset is necessary to switch the supply back
to the inverter.
1.5 MANUAL
BYPASS
To safely allow maintenance and repair of the unit, UPS is provided with a manual
bypass switch.
In this mode all the testing activities to verify the efficiency of the system can be
carried out safely. Manual bypass must be inserted by following the instructions given in
the operating manual. During the transfer to manual bypass there is no interruption of
the supply to the load.