Ungrounded Installation - Siemens SIMATIC Distributed I/O System DP/ASi Link Manual

Installing and Wiring the DP/ASi Link
4.2.2

Ungrounded Installation

Definition
With ungrounded installation of the 24V supply to the DP/ASi link, there is
no link between the external power supply (terminal G) and PI, thus resulting
in the protective conductor loosing its protective function.
Due to the internal design of the DP/ASi link, the supply voltage is connected
capacitively to the protective conductor. This results in high-frequency inter-
ference being diverted.
Rules
For ungrounded installation you must pay attention to the following points:
Warning
!
Ungrounded installation may be canceled by grounded machine parts or
grounded electrical apparatus.
Example: A grounded sensor or a grounded signal control element connects
the PI to the chassis ground potential of the PLC.
4-6
You have to provide a master switch (1) conforming to VDE 0100 for the
DP/ASi link.
For the connection of the external power supply (24 VDC) to the supply
system, you require a fuse (2).
For the power supply use a Siemens Series 6EV1 external power supply
(refer to catalog ET 1).
If you connect other external power supplies (24 VDC), make sure that
the voltage is between 20 and 30 V (including ripple). The external power
supply must generate a functional extra-low voltage with safe electrical
isolation in accordance with VDE 0106, Part 101. For non-stabilized ex-
ternal power supplies, you require a backup capacitor (200 F per 1 A
load current, (3)).
The 24 VDC supply should be fused separately (5).
With both grounded and ungrounded installation,connect the PI connec-
tion of the DP/ASi link in a low-resistance manner to the protective con-
ductor (6).
On the right side of the DP/ASi link and of the power supply connector
there is a screw for connecting the protective conductor.
The protective conductor terminal of the DP/ASi link is connected inter-
nally to a pin 9 of the circular connector (refer to Table 4-3).
Provide isolation monitoring to earth with voltage clamping (7).
Distributed I/O System DP/ASi Link
EWA 4NEB 710 6055-02b