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Figure 6-1
Parallel connection
6.2.2 Parallel
Redundant
Mode
At this mode if one of the UPS fails, the other UPS continues to feed load.
Assume that UPS1 on figure 6-1 is failed, SB1 and SB2 static switches shall turn off and the UPS 1
is isolated from load.
The SB4 static switch of the UPS 2 shall stay in conducted position and it continues to feed the
load.
If UPS 1 is operating after a delay this UPS will join the system.
If two UPSs fail than SB3 static switches shall turn on and load is transferred to bypass
This is a 3 level redundancy UPS1+UPS2,UPS2 ,mains
Current sharing is active in this mode.
Hot
Standby
Mode
In this mode UPS 1 feeds the load and the UPS 2 waits spare, there is no current, it is in standby
mode but it is ready to work.
If a failure occurs on UPS 1, static switch system shall isolate UPS 1 from load and activate the
UPS 2, this is a very fast response.
Current sharing is not active in this mode.
MB1
SB1
UPS1
CB1
AC/DC -1
BATT.1
INVERTER 1
SB2 CB2
MB2
SB3
UPS2
CB3
AC/DC -2
BATT.2
INVERTER 2
SB4 CB4
LINE
OUTPUT
