Siemens SITOP PSE200U, SITOP SEL1200, SITOP SEL1400 User manual
Brochure
Edition
/
SITOP power supply
Electronic protection and
fast fault localization in
V DC load circuits
SITOP SEL, SEL, PSEU
selectivity modules
usa.siemens.com/sitop
The SITOP selectivity modules distribute the load current
across several 24 V DC load circuits and monitor them
reliably for overload and short-circuit conditions. The
electronics permit brief current peaks caused, for example,
by high inrush currents, but isolate load circuits in the event
of an extended overload. This is ensured even on highresistance lines. In such cases, miniature circuit breakers
fail to trip, or trip too late, even if the power
supply unit could deliver the required tripping current. The
SITOP expansion modules continue to reliably supply 24 V
to the load circuits not affected by an overload and can
prevent a total system failure.
The new SITOP SEL selectivity modules, which have more
outputs, an additional tripping characteristic and detailed
diagnostics, now offer even more efficient protection for
your plant.
Miniature circuit breakers with high current consumption
Miniature circuit breakers are often still used for the selective
protection of 24 V DC load circuits. In many cases, however,
when interacting with switched-mode power supply units, they
do not offer reliable protection. They require several times the
rated current in order to trip within a few milliseconds. Because
stabilized power supplies limit their output current
electronically when there is a critical overload, the tripping
current is not always guaranteed. This can cause the 24-V
supply to break in and the PLC to go to Stop. Even if the power
supply unit could supply the current, immediate tripping is not
necessarily assured, because with this high current
requirement, the line resistance can no longer be neglected. It
prevents the required tripping current from flowing. Therefore
fast tripping is only possible up to certain cable lengths and
starting from larger cable cross-sections. In addition to the line
resistance, the overall circuit design (e.g. contact resistances at
terminals) must be taken into consideration when configuring
miniature circuit breakers.
SITOP selectivity modules – optimized for switched-mode
power supply units
The selectivity modules are specially designed to protect
24 V DC individual load circuits supplied by switched-mode
power supplies. Individual setting of the tripping current allows
optimum adaptation to the respective load circuit. Engineering
effort is minimal since the switch-off characteristic always
guarantees reliable tripping – even with high line impedances
that limit the short-circuit current.
HMI
Selectivity
Power supply
As an electronic monitor, the SITOP selectivity module switches faulty 24 V DC load circuits off immediately, and continues to supply the other loads
without any interruption.
module
24 V DC
Actor/SensorPLC
G_KT01_XX_01567
SITOP PSE200U and SEL1400 – limiting characteristic offers
maximum safety
In terms of the tripping characteristic, the new 8-channel
SEL1400 modules behave like the tried and tested 4-channel
PSE200U modules. They limit the output current to 150% of the
set value, corresponding to the overload behavior of the SITOP
power supplies of the Advanced and Standard product lines.
This means that, even in the case of a short circuit, no overload
can occur and consequently no voltage drop at the output of
the power supply unit.
Even when a power supply without overload reserves is used,
the patented SITOP concept ensures reliable protection: The
electronics continuously monitor the 24 V DC input voltage. As
soon as the 24 V DC threatens to fail, the path with a higher
current than the set current is disconnected immediately. All
other load circuits continue to be supplied without interruption.
Even loads that do not comply with the PLC standard and can
only bridge a few milliseconds of undervoltage, continue to
operate without any problem.
Tripping characteristics
SITOP SEL1200 – switching characteristic for standard
protection
The new SEL1200 8-channel selectivity modules also allow
higher, brief overload currents. The higher the current, the
faster the output is shut down. It is possible that the power
supply is loaded for a few milliseconds with a current
significantly higher than that which is set. If the power
supply unit only has limited overload reserves, it may result in
a momentary drop in the 24 V supply. For loads that comply
with the PLC standard, however, this is not critical. For standard applications, the SEL1200 selectivity module therefore
offers very efficient protection.
For 24 V loads with a high inrush current, the switching
characteristic even offers advantages, since whatever applies
at shutdown also applies when switching on. High currents
are not limited, but can be permitted for a short time. In addition, two outputs of the SITOP SEL1200 or 1400 selectivity
modules can be connected in parallel for a 15 A rated
current.
Time in
seconds
100
Normal operation
Switch-off after approx. 5 s
0.1
0.01
10
5
1
Current limitation to 150% for approx. 100 ms,
then switching off the faulty output
0
SITOP SEL1400 / PSE200U characteristic: limiting
Shutdown response for current requirement per output
circuit relative to set value (I/I set value = 100%):
Power requirement: Shutdown after:
From 0 A to 100% (set value) No shutdown
From set value to 150%
Above 150%
Above set value with
simultaneous collapse of supply
voltage below 20 V DC
1)
1)
of set value Current limiting to approx.
Approx. 5 seconds
1)
150%
for typ. 100 ms, then
shutdown
Immediate shutdown
Switching
SITOP SEL1200
Limiting
SITOP SEL1400/PSE200U
The higher the current,
the faster the trip
250% I-set200%180%150%100%
SITOP SEL1200 characteristic: switching
Shutdown response: The higher the current, the faster the
faulty output is shut down, in line with the limit load
2
integral i
t.
Startup characteristics: Supports loads with high inrush
current, whereby the supply voltage can drop to 15 V
G_KT01_XX_01573
Startup characteristics: Load ramp-up to 150% of set value
with stable voltage supply of at least 20 V
1)
SITOP PSE200U versions with NEC Class 2: 110%
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