7
Ultron NT Series
When maintenance is needed and the reserve AC power is normal, the UPS can
be switched from inverter mode to bypass mode manually with continuous power
delivering to the loads. Under such conditions, the internal power will be completely
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As a result, risks will not exist in the UPS so service personnel can perform
maintenance safely (see
Figure 3-4
).
3.5 Normal Mode (Parallel)
Figure 3-5: Normal Mode Block Diagram_ Parallel Units
RECTIFIER INPUT
RESERVE
MAINS
BREAKER
RESERVE INPUT
BREAKER
MANUAL BYPASS
BREAKER
OUTPUT
BREAKER
Power Flow
BATTERY BANK
Power Flow
STATIC SWITCH
INVERTER
RECTIFIER
RECTIFIER INPUT
RESERVE
MAINS
BREAKER
RESERVE INPUT
BREAKER
MANUAL BYPASS
BREAKER
OUTPUT
BREAKER
Power Flow
BATTERY BANK
Power Flow
STATIC SWITCH
INVERTER
RECTIFIER
Power Flow
LOAD
UPS 1
UPS 2
Power Flow
Power Flow
Power Flow
Power Flow
Two or more UPS units operating in parallel mode have to satisfy requirements of
the same capacity, output voltage, frequency, and equal load share. If one of the
units fails and its loads are less than the sum of rated-load values of other units in
parallel, the rest of units can share the sum of loads; otherwise, all UPS units will
shut down inverters and switch to the reserve AC power to supply power to the
loads (see
Figure 3-5
).
