Galvanic Isolation - ABB PP885 Hardware And Installation Manual

Section 7 Additional Installation Tips
If there is a substantial distance between the relay contacts for 24 V DC and
230 V AC, it is OK to use the same 24 V devices for all feeds. See 3 in drawing
above.
Connect 0 V on the 24 V feed to the ground, see 4 in drawing above. This offers
three advantages:
• Safety is increased. The 24 V feed is not live in the event of a faulty connection
or short circuit between 0 V (24 V) and 230 V phase.
• Transients on the 24 V feed are connected to the ground.
• No risk that the 24 V feed is at a high level in relationship to the ground. This
is not unusual since there is high static electricity.

Galvanic Isolation

The operator panel has galvanic isolation against the 24 V DC feed but no galvanic
isolation between the communication ports for RS232, RS422/485 and USB. Only
the Ethernet connection has galvanic isolation.
3BSE069463-600 Rev C
DC/DC
galvanic isolation
Filter
+24 V DC
0 V
1.5 m
Operator panel
RS422 RS232
*
PC
*
Internal electronics
VCC
0 V (GND)
RS422/485 RS232
Modular controller
USB
*
*
Different ground potential
*
= Internal 0 V (GND) connection
Galvanic Isolation
Ethernet
DC/AC
CFL
USB USB
Printer
Power CPU COM COM2
* * *
*
PC
*
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