Rockwell Automation 1398-DDM-xxx ULTRA 100 Series Drives Installation Manual - Manual (Page 281)

Publication 1398-5.2 – PDF 1997
Electromagnetic Compatibility Guidelines for Machine Design E-8
1. Motor cables must have a continuous shield and be terminated at
both ends. The shield must connect to the ground bus bar or drive
chassis at the drive end, and the motor frame at the motor end. Use
of a properly shielded motor cable is essential to meet European
EMC requirements.
2. Signal cables (encoder, serial, analog) should be routed away
from the motor cable and power wiring. Separate steel conduit can
be used to provide shielding between the signal and power wiring.
Do not route signal and power wiring through common junctions
or raceways.
3. Signal cables from other circuits should not pass within 300 mm
(1 ft.) of the drive.
4. The length or parallel runs between other circuit cables and the
motor or power cable should be minimized. A rule of thumb is
300 mm (1 ft.) of separation for each 10 m (30 ft.) of parallel run.
The 30 mm (1 ft.) separation can be reduced if the parallel run is
less than 1 m (3 ft.).
5. Cable intersections should always occur at right angles to mini-
mize magnetic coupling.
6. The encoder mounted on the brushless servo motor should be con-
nected to the amplifier with a cable using multiple twisted wire
pairs and an overall cable shield. Encoder cables are offered in
various lengths that have correct terminations.
Persistent EMI problems may require additional countermeasures.
The following suggestions for system modification may be attempted.
1. A ferrite toroid or “doughnut” around a signal cable may attenuate
common mode noise, particularly RS-232 communication prob-
lems. 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 timers).
3. DC coils should be suppressed with a “free-wheeling” diode con-
nected 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.