Connection
6.2 Power supply
SCALANCE W778-1 / W738-1
54 Operating Instructions, 03/2022, C79000-G8976-C450-07
6.2 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
Note
All power supplies (24 V power supply unit or PoE) must not be connected to a main
supply higher than 300 V and the overvoltage category II.
Information on the power supply
• There are two options for the power supply:
– Direct infeed via the four-pin M12 connection socket ①
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.
– Power over Ethernet via the M12 Ethernet interface P2 ②.
The power supply cannot be connected redundantly.
• For the direct infeed 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 mm
2
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 NEC or CEC applies: Type PTLC or ITC
• To connect the functional ground, use a copper cable of category 20 AWG or a cable
with a cross-section ≥ 0.75 mm².
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