Connecting up 
  5.4 24 VDC power supply 
SCALANCE XR-300WG 
Operating Instructions, 05/2017, C79000-G8976-C454-01 
41 
 
24 VDC power supply 
Safety extra low voltage 
 
The device is designed for operation with a directly connectable safety extra-low voltage 
(SELV). 
 
 
Suitable fusing for the power supply cables 
The current on the terminal may not exceed 5 A. Use a fuse that protects against currents > 
5 A. The fuse must meet the following requirements: 
•  In areas where NEC or CEC applies: 
–  Suitable for DC (min. 60 V / max. 5 A) 
–  Breaking current at least 10 kA 
–  Approval according to ANSI/UL 248-1 or CSA C22.2 No. 248.1 
–  Classes R, J, L, T or CC 
–  Suitable for the protection of DC power supply circuits 
•  In other areas: 
–  Suitable for DC (min. 60 V / max. 5 A) 
–  Breaking current at least 10 kA 
–  Approval in compliance with IEC 60127-1 / EN 601127-1 
–  Switch off characteristics: B or C for circuit breakers and fuses 
–  Suitable for the protection of DC power supply circuits 
You do not need to fuse the supply cable if you only use power sources with a limited 
power source (LPS) or power sources according to NEC Class 2 for the power supply of 
the devices.