Planning the electrical installation 55
Protecting the relay output contacts and attenuating
disturbances in case of inductive loads
Inductive loads (relays, contactors, motors) cause voltage transients when switched
off.
The relay contacts on the RMIO board are protected with varistors (250 V) against
overvoltage peaks. In spite of this, it is highly recommended to equip inductive loads
with noise attenuating circuits [varistors, RC filters (AC) or diodes (DC)] in order to
minimize the EMC emission at switch-off. If not suppressed, the disturbances may
connect capacitively or inductively to other conductors in the control cable and form
a risk of malfunction in other parts of the system.
Install the protective component as close to the inductive load as possible. Do not
install protective components at the RMIO board terminal block.
24 V DC
230 V AC
X25
1RO1
2RO1
3RO1
X26
1RO2
2RO2
3RO2
X27
1RO3
2RO3
3RO3
Relay outputs
RMIO
230 V AC
Diode
Varistor
RC filter
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