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5.2
Power supply
Note
Galvanic isolation of the power supply unit
To ensure dielectric strength according to IEEE 802.3, the supplying 24 V power supply unit
must be galvanically isolated with a dielectric strength of 1500 VAC. The galvanic isolation
must also not be bridged by other devices connected to the same power supply unit.
Note
All power supplies (24 V power supply unit or PoE) must not be connected to a mains supply
higher than 300 V and the overvoltage category II.
Information on the power supply
● For the power supply, there are two options with the SCALANCE W778/W738:
– Direct feed in via the four-pin M12 socket (position
– Power over Ethernet via the M12 Ethernet interface P2 (position
● For the direct feed-in of the power supply use copper cables with the following properties:
– Round cable cross-section with 6 to 8 mm diameter.
– Two-wire cable with 0.5 to 1.5 mm2 cross-section per wire.
– Permitted tensile load at least 100 N. - UL
– Listing of the cables according to the national installation regulations. In areas where
● To connect the functional ground, use a copper cable of category 20 AWG or a cable with
a cross-section ≥ 0.75 mm².
SCALANCE W778-1 /W738-1
Operating Instructions, 07/2019, C79000-G8976-C450-04
The power supply can be connected redundantly. The inputs L1/L2 are decoupled
There is no distribution of load. The power supply unit with the higher output voltage
supplies the device alone.
The power supply cannot be connected redundantly.
NEC or CEC applies: Type PTLC or ITC
5.2 Power supply
①
)
②
).
Connection
41
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