Overload Protection In The 24 V Output Circuit - Siemens SITOP PSU100S Operating Instructions Manual

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9.4 Overload protection in the 24 V output circuit

9.4 Overload protection in the 24 V output circuit
If overload occurs, the electronic current limiting of the SITOP PSU100S power supply limits
the output current to a maximum value (refer to chapter Technical data (Page 39)). The
output cables are protected against a thermal overload if they are dimensioned
corresponding to the maximum rms output current, or protected using additional components
(for example, miniature circuit breaker, fuses).
However, a load circuit that fails as a result of overload, for instance, should frequently be
reliably and quickly identified and specifically switched off before the power supply goes into
current-limiting mode (in current-limiting mode, the supply voltage would also be reduced for
all of the remaining 24 V loads).
The SITOP PSE200U selectivity module with 4 channels (versions with adjustable output
current range for each channel from 0.5-3 A and 3-10 A) is available; this monitors the 24 V
branches for overloading and short-circuiting (Figure 9-4 Electronic protection of 24 V loads
using the SITOP PSE200U selectivity module (Page 64)). Brief current peaks, e.g. as a
result of a high inrush current, are permitted, and branches with a longer overload are
switched into a no-current condition. This is also ensured for cables in a high-ohmic
condition and for short-circuits that slowly develop over time.
When a channel fails, the fault is signaled using a group signal contact or as a single
channel signal, and the branch of the module involved is displayed using an LED.
For versions with single channel signaling, function blocks for evaluation purposes are
available for SIMATIC S7-1200/300/400, for STEP 7 Classik and TIA Portal at no charge.
You can find additional information at:
SITOP PSE200U selectivity module manuals
(http://support.automation.siemens.com/WW/view/en/10807226/130000)
Figure 9-4
64
Electronic protection of 24 V loads using the SITOP PSE200U selectivity module
Operating Instructions, 02.2013, C98130-A7589-A1-3-7629
SITOP PSU100S