Siemens SCALANCE XR-300WG Series Operating Instructions Manual page 42

Connecting up
5.4 24 VDC power supply
Overvoltage protection for the power supply cables
If SCALANCE XR-300WGs are supplied over long 24 V power supply lines or networks,
measures are necessary to prevent interference by strong electromagnetic pulses on the
supply lines. These can result, for example, due to lightning or switching of large inductive
loads.
One of the tests used to attest the immunity of the SCALANCE XR-300WG to
electromagnetic interference is the "surge immunity test" according to EN 61000-4-5. This
test requires overvoltage protection for the power supply lines. The following type is, for
example, suitable:
Dehn Blitzductor BVT AVD 24, order number 918 422
Manufacturer: DEHN + SÖHNE GmbH + Co. KG, Hans Dehn Str. 1, Postfach 1640, D-
92306 Neumarkt, Germany.
Information on the power supply
● The power supply is connected using two 2-pin plug-in terminal blocks). The terminal
blocks ship with the device.
● The power supply can be connected redundantly. Both inputs are isolated. There is no
distribution of load. When a redundant power supply is used, the power supply unit with
the higher output voltage supplies the SCALANCE XR-300WG alone.
● The power supply is connected over a high resistance with the enclosure to allow an
ungrounded set up. The two power inputs are non-floating.
● Note the wiring rules.
Position and assignment
Figure 5-1
Contact
L1
M
42
CAUTION
Position of the terminal block on the SCALANCE XR-300WG
Assignment
+24 VDC
Ground
Contact
L2
M
Operating Instructions, 05/2017, C79000-G8976-C454-01
Assignment
+24 VDC
Ground
SCALANCE XR-300WG