ABB OmniCore V400XT Product Manual page 77

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.
xx1200000961
Product manual - OmniCore V400XT
3HAC081697-001 Revision: A
+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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3 Installation and commissioning
3.5.2 Connecting cables to the controller
0 V
1)
2)
0 V
3)
Continued
77