
Commissioning
Operating Instructions SCALANCE W 744-1PRO
20 C79000-G8976-C185-03
Notes on Power Supply and Grounding
!
Warning
The SCALANCE W744-1PRO device is designed for operation with safety extra-
low voltage (SELV). This means that only safety extra-low voltages (SELV) with
limited power source (LPS) complying with IEC950/EN60950/ VDE0805 can be
connected to the power supply terminals.
The power supply unit to supply the SCALANCE W744 must comply with NEC
Class 2 (voltage range 18 - 32 V, current requirement 1 A)
The subject unit is to be supplied by a Class 2 power source complying with the
requirements of the National Electrical Code, table 11 (b). If power is redundant
supplied (two individual power sources) the power sources together should comply
with the requirements of the National Electrical Code, table 11 (b).
Exceptions:
Power supply with PELV (according to VDE 0100-410) is also possible if the gen-
erated rated voltage does not exceed the voltage limits 25 V AC or 60 V DC.
Power supply by a SELV power source (according to IEC 60950) or PELV power
source (according to VDE 0100-410) without limited power is also permitted if
suitable fire protection measures are taken by:
- Installation in a cabinet or suitable enclosure
- Installation is a suitably equipped, closed room
Caution
There must be no potential difference between the following parts, otherwise there
is a risk that the device could be destroyed:
• Ground potential of the power supply and the ground potential of the antenna
ground.
• Ground potential of the power supply and a grounded enclosure.
• Ground potential of the power supply and the ground potential of the device
connected to Industrial Ethernet (for example, PC, AS-300, AS-400 etc.).
Connect both grounds to the same foundation earth or use an equipotential bond-
ing conductor.
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