ABB OmniCore C30 Product Manual page 90

3 Installation and commissioning
3.5.2 Connecting cables to the controller
Continued
Example 1:
Example 2:
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.
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• 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.
• 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.
+24 V DC
+24 V AC/DC
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).
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Product manual - OmniCore C30
3HAC060860-001 Revision: P