Electromagnetic Compatibility (EMC)
Installation Manual PSSuniversal
21262-EN-07
13
3.2.5
Screening
Interference currents must be diverted to cable shields via shield bars.
Please note:
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Connect the shields with low impedance to the shield bar or earth bar.
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Use cables with braided shield, with a minimum cover area of 80 %.
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When laying cables without equipotential bonding or using foil shields: Connect the
shield at one end.
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If possible, use metal or metallised plugs to connect cables for serial data transfer. Al-
ways refer to the regulations relating to the fieldbus systems.
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If the shield is not to be connected at the end of the cable, it must have no connection
to the connector housing.
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At the point where the cable enters the cabinet, connect the shield to the earth bar,
without making a break in the cable. Use metal cable clamps which cover the shield
over a wide surface area. Take the screen as far as the PSSuniversal, but do not lay it
on top of the PSSuniversal.
Digital inputs and outputs on the PSSu system do not need shielded cables. However, if the
connection cables have a shield, it should be connected at one end.
Analogue inputs and outputs plus the inputs and outputs on the counter modules should al-
ways be connected using shielded cables.
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On base modules with C-rail:
– Connect the shield to the terminals on the C-rail.
– Connect the C-rail with low impedance to the functional earth.
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On analogue modules and base modules without C-rail:
– Connect the shield as shown in the terminal configuration section of the configura-
tion data sheets.
– The module connects the shield to the functional earth via the mounting rail.
3.2.6
Suppression on inductive loads
Suppression should not be used to protect the digital semiconductor outputs.
Digital semiconductor outputs on the PSSuniversal do not need suppression. With FS out-
puts on the PSSuniversal, suppression can lead to errors on the on/off tests and test
pulses.
However, inductive loads that are not switched by the PSSuniversal should be wired with
suppression elements for EMC reasons.
3.2.7
Installing within an enclosure or wall-mounting
Care must be taken to avoid interference when installing the unit within an enclosure or
wall-mounting:
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Earth bars, earth conductors and the housing should be attached to metal parts in order
to divert any coupled interference on to large metal areas. For wall-mounting we recom-
mend: that the overall potential surfaces are made of steel.