Connecting the PSSu system
Installation Manual PSSuniversal
21262-EN-07
42
WARNING!
Risk of electrocution!
If voltages higher than 50 VAC or 120 VDC are connected to the PSSuni-
versal, e.g. to switch contacts on relay modules, please note the following:
– Specific accident prevention regulations apply.
– The C-rail of the supply group should only be connected to the pro-
tective earth (PE).
6.2
Power supplies
Please note:
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The external power supplies must conform to EN 60950, 03/97, section 2.3, EN 60742,
9/95 or EN 50178, 10/97.
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On supply groups with an earthed supply: The module supply and periphery supply re-
quire a common 0 V reference potential.
– Connect together the 0V connections on all the external power supplies and earth
the 0 V mains at a single point.
– Earthed supply voltages offer the best noise immunity.
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On floating supply groups: Do not earth the 0 V supply on the module supply and peri-
phery supply.
– Please note the regulations on insulation monitoring and safe electrical isolation.
– The 0 V supply on the module supply is always looped through across the whole
module bus of a PSSu system, even when the supply groups are different.
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The connection of the 0 V supply to the central earth bar or earth fault monitor must be
in accordance with national regulations (e.g. EN 60204-1, NFPA 79:17-7, NEC: Art-
icle 250).
