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3
Operation Modes
3.6 Normal Mode (Parallel)
The UPS can be paralleled (at maximum eight) to increase capability and redundancy.
UPSs with the same capacity, voltage and frequency can be paralleled.
BYPA.
BYPA.
UPS 1
LOAD
UPS 2
MAIN
MAIN
Q3 Switch
Q2 Switch
Q1 Switch
Rectifier Inverter
Circuit
Breaker
Batteries
STS
Q4 Switch
Q3 Switch
Q2 Switch
Q1 Switch
Rectifier Inverter
Circuit
Breaker
Batteries
STS
Q4 Switch
(Figure 3-6: Path of Electrical Power through the Parallel UPSs in Normal Mode)
In normal mode (parallel), the total load will be equally shared by parallel UPSs. If one of
the parallel units fails and its load is less than the total capacity of the remaining parallel
units, the failing UPS output will be switched off and its load will be equally shared by the
other units. If the failing UPS load is larger than the total capacity of the remaining parallel
units, all UPSs’ inverters will turn off and the total load will be supplied by bypass power.
During normal mode, all parallel UPSs’ LEDs illuminate as follows.
Fault
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