ABB OmniCore C30, Product Manual

Page: 90 / 606

Example 1:
• Where a good earth connection is available on all units, the best shielding
is obtained by grounding all screens at both ends on all units.
Example 2:
• If the cable is terminated where a good earth connection is not available a
noise suppression capacitor can be used. The screens of the 2 cables must
be connected as shown in the figure, but not connected to the chassis of the
unit.
Interference elimination
Internal relay coils and other units that can generate interference inside the control
cabinet are neutralized. External relay coils, solenoids and other units must be
clamped in a similar way. The illustration below shows how this can be done.
Note that the turn-off time for DC relays increases after neutralization, especially
if a diode is connected across the coil. Varistors give shorter turn-off times.
Neutralizing the coils lengthens the life of the switches that control them.
0 V
+24 V DC
1)
2)
3)
0 V
+24 V AC/DC
xx1200000961
1 The diode should be dimensioned for the same current as the relay coil, and
a voltage of twice the supply voltage.
2 The varistor should be dimensioned for the same energy as the relay coil,
and a voltage of twice the supply voltage.
3 When AC voltage is used, the components needs to be dimensioned for >500
V max voltage and 125 V nominal voltage.
The resistor should be 100 Ω, and the capacitor should be 1W 0.1 - 1 µF
(typically 0.47 µF).
90 Product manual - OmniCore C30
3HAC060860-001 Revision: P
© Copyright 2019-2022 ABB. All rights reserved.
3 Installation and commissioning
3.5.2 Connecting cables to the controller
Continued