Rockwell Automation 1398-DDM-xxx USE MNL/ULTRA 200 DIG.SERVO.DR - Manual (Page 286)

Publication 1398-5.0 – October 1998
E-6 Electromagnetic Compatibility Guidelines for Machine Design
Shielding and Segregation
The EMI radiating from the drive enclosure drops off very quickly
over distance. Mounting the drive in an enclosure, such as an
industrial cabinet, further reduces the radiated emissions.
The primary propagation route for EMI emissions from a drive is
through cabling. The cables conduct the EMI to other devices, and can
also radiate the EMI. For this reason, cable segregation and shielding
are important factors in reducing emissions. Cable shielding can also
increase the level of immunity for a drive.
The following suggestions are recommended for all installations,
especially since they are inexpensive.
1. 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.
2. Signal cables from other circuits should not pass within 1 foot of
the drive.
3. The length or parallel runs between other circuit cables and the
motor or power cable should be minimized. A rule of thumb is 1
foot of separation for each 30 feet of parallel run. The 1 foot sepa-
ration can be reduced if the parallel run is less than 3 feet.
4. Cable intersections should always occur at right angles to mini-
mize magnetic coupling.
5. Do not route any cables connected to the drive directly over the
drive vent openings. Otherwise the cables will pick up the emis-
sions leaked through the vent slots.
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. Allen-Bradley offers encoder
cables in various lengths that have special terminations.
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.