THOMSON Omnidrive Series Installation Manual page 181

C-6 Electromagnetic Compatibility Guidelines for Machine Design
1. A ferrite toroid or "doughnut" around a signal cable may attenuate common mode noise, particu-
larly RS-232 communication problems. However, a ferrite toroid will not help differential mode
noise. Differential mode noise requires twisted wire pairs.
2. Suppress each switched inductive device near the servo amplifier. Switch inductive devices
include solenoids, relay coils, starter coils and AC motors (such as motor driven mechanical tim-
ers).
3. DC coils should be suppressed with a "free-wheeling" diode connected across the coil.
4. AC coils should be suppressed with RC filters (a 200 Ohm ½ Watt resistor in series with a 0.5
uF, 600 Volt capacitor is common).
Following these guidelines can minimize noise problems. However, equipment EMC performance must
meet regulatory requirements in various parts of the world, specifically the European Union. Ultimately,
it is the responsibility of the machine builder to ensure that the machine meets the appropriate requirements
as installed.
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