5 Electrical connections
5.2.3 Interference elimination
84 A 3HAC 16245-1
5.2.3 Interference elimination
External units External relay coils, solenoids, and other units that will be connected to the controller must
be neutralized. The figure below illustrates how this can be done.
The turn-off time for DC relays increases after neutralisation, especially if a diode is connected
across the coil. Varistors give shorter turn-off times. Neutralising the coils lengthens the life of
the switches that control them
Clamping with a
diode
The diode should be be dimensioned for the same current as the relay coil, and a voltage of
twice the supply voltage.
xx0100000163
Clamping with a
varistor
The varistor should be be dimensioned for the same current as the relay coil, and a voltage of
twice the supply voltage.
xx0100000164
Clamping with an
RC circuit
R 100 ohm, 1W C 0.1 - 1 mF. >500V max. voltage, 125V nominal voltage.
xx0100000165
+24V
0V
+24V 0V
+24V DC,
or AC voltage 0VRC
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