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Power Supplies for Programmable Controllers and I/Os
3.4
Power Supplies for Programmable Controllers and I/Os
3.4.1
Power Supplies for Control
Systems with SIMATIC S5
Power supply for the PLC
circuits
Load power supply for the
I/Os
Ratings of load power supplies The electronic short-circuit protection of digital output modules only
3 - 22
This section describes:
• • Which circuits you must distinguish in the control system and
which demands are made on the power supply.
• • Connection and grounding concept with higher-level infeed from
grounded, centrally grounded and ungrounded supplies.
• • Connecting the power supply to non-isolated and isolated modules.
For control systems with SIMATIC S5, you will need:
• • A power supply for the internal PLC circuits (control power
supply)
• • and a load power supply for the input and output circuits.
The power supply for the internal PLC circuits powers the CPU and
the modules used.
Note
Ensure that the control power supply is not overloaded. Make a
current addition and estimate the current drawn by all modules.
The load power supply feeds the input and output circuits (load
circuits) as well as sensors and actuators. Only a power supply which
offers safe electrical isolation from the AC system may be used for the
24 V DC supply.
Caution
Only safety-separated low voltage DC ≤ 60 V may be used for the
24 V DC supply. The safety separation can be implemented
according to the requirements of, amongst other sources,
VDE 0100, Part 410/HD 384-4-41/IEC 364-4-41 (functional
extra-low voltage with safety separation) or
VDE 0805/EN 60950/IEC 950 (safety extra-low voltage SELV) or
VDE 0106, Part 101.
responds when 3-times the rated current is exceeded. You should
therefore so design the load power supply units that the unit can
supply the current required for shutting down in the event of a
short-circuit at one output.
System Manual
C79000-B8576-C199-03
- Quick Links:
- S5-135U/155U
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