Filtration; Interference Suppression Of Inductors - Siemens SIROTEC Planning Manual

7 Filtration

The filtration is a supplementary EMC measure for shielding and is used to
decouple the grid-bound interference sizes. Because of this, the filters are inserted
into the grid-bound transmission path between the interference source and
interference sink. Filters reduce the grid-bound radio interferences and increase
the noise immunity of electrical facilities without the disadvantageous influence of
the transmission of the information signals.

7.1 Interference suppression of inductors

Inductive interference sources
Relays, contactors, valves, motor brakes, principally all solenoids (inductors),
generate inductive voltages when shutting down and must be therefore
radioshielded by wiring.
Induction voltages of 800 volts arise in 24 V coils and in 230 V coils several 1000 V
can be adjacent to the switch when the coil is switched off.
Interference suppression by wiring
When using, for example, RC wirings the very high interference voltages of
switched coils can be prevented. The wiring considerably reduces the interference
voltage and thus also their decoupling in lines which are routed parallel to the coil
line.
Notes
·
On assemblies are only suitable for the wiring of the line inductivity. They do
not replace the direct coil wiring.
·
The coil wiring must be performed directly on the coil.
© Siemens AG, 2004. All rights reserved
EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition
7-45