Safety - ABB PP882 Hardware And Installation Manual

Safety

Safety
Most of the operator panels are fed with 24 V DC.
If a power supply that meets safety standards is used and only feeds the operator
panel, there is no problem. See 1 in drawing above.
However, if a 24 V unit that also feeds other units is used, there is reason to be
cautious, see 2 in drawing above. The operator panel does not have insulation
that meets safety requirements in the event of a potential short circuit between
230 V AC and 24 V DC. It is assumed that the 24 V feed is secure, for example,
SELV according to EN 60950 (protection against electric shock) and UL 950.
Here is an example that explains why a secure 24 V DC feed can be ruined
by mixing 24 V relay contacts with 230 V AC relay contacts in a smaller
controller. Check that the clearances and creepage distances between 24 V DC
and 230 V AC fulfill EN 60950 or UL 950. If not, input a separate 24 V unit
into the operator panel.
40
Power supply
230 V AC to 24 V DC
+24 V
1
0 V
4
Power supply
230 V AC to 24 V DC
+24 V
2
0 V
4
Distance?
Power supply
230 V AC to 24 V DC
+24 V
3
0 V
4
230 V AC
Section 7 Additional Installation Tips
Operator panel
Operator panel
Operator panel
Small controller with expansion unit
COM1 Ch0
Ch1
COM100
Ch100
Ch101
5355
3BSE069462-600 Rev D