21
A
C
in
pu
t
N
R
-S
-T
A
C
by
pa
ss
A
C
in
pu
t
N
R
-S
-T
N
R
-S
-T
N
U
-V
-W
A
C
sal
id
a
N
U
-V
-W
A
C
out
put
(Q5)
Maintenance line (manual Bypass).
(Q1a)
Emergency line (static Bypass).
(Q2)
(Q3)
Normal operating.
Mains fault.
Operating with inverter non-active (EPO condition to «Off»).
Operating over manual bypass.
Fig. 20.
UPS single line diagram with operating flows.
(Q5)
(Q4a)
(Q1a)
Maintenance line (manual Bypass).
Emergency line (static Bypass).
(Q2)
(Q3)
Normal operating.
Mains fault.
Operating with inverter active (EPO condition to «On»).
Operating over manual bypass.
Fig. 21.
UPS-B single line diagram with operating flows.
4.3.5. Static bypass stage.
When the inverter can't keep the voltage to the critical loads due to
overloads, short-circuits, current limits or faults, the UPS has a
bypass circuit, which supplies isolation for the inverter and supplies
the critical loads directly from
electrical mains.
The UPS controls the availability of inverter and bypass mode
permanently in order to make the shifting between them.
The bypass stage is based on six double thyristors in semipack
format, working as AC switches, three of them are for s
hifting the
input over the output and the other three are for shifting the inverter
over the output.
The managing system of the SCR switches is based on drivers
designed with a shifting system that responds to the following
requirements:
Full static shifting system.
Shifting with no high transient currents.
Shifting with no transfer time.
The control algorithm of the triggering signals of the thyristors
assures a nil transfer time, and avoids short-circuits between the
thyristors of bypass and inverter (shifting with zero cross current).
4.3.6. Maintenance or manual Bypass.
.
All UPSs from this series are foreseen with an auxiliary line
protected by a circuit breaker switch, which makes an electrical
bridge between the input and output terminals.
Managing this switch, properly together with the input and output,
allows isolating electrically all the UPS elements from the electrical
lines.
The type of maneuvering of the maintenance bypass is “make
before break”, with the purpose of keeping the critical loads fed,
even during the maintenance tasks.