Parker OEM750, Руководство пользователя

Страница: 79 / 96

OEM750/OEM750X • EMC INSTALLATION GUIDE
71
C
ONTROL
S
IGNAL
C
ONNECTIONS
High-quality braided-screen cable should be used for control
connections. In the case of differential inputs, it is preferable
to use cable with twisted pairs to minimize magnetic coupling.
This applies to both analog and digital signals. Control cables
leaving the enclosure should have the cable screen returned
to a local ground point near the product. Where screened
leads are used in control circuits that are only opto-isolated at
one end, the screen must be referenced to earth at the non-
isolated end. Where there is isolation at both ends of the
connection, earth the screen at the receiving end. This is to
give protection against coupled noise impulses and fast
transient bursts.
Remember to route control signal connections well away from
relays and contactors—at least 8 inches (200 mm). Control
wiring should not be laid parallel to power or motor cables
and should only cross the path of these cables at right angles.
Bear in mind that control cables connected to other
equipment within the enclosure may interfere with the
controller or drive, particularly if they have come from outside
the cabinet. Take particular care when connecting external
equipment with the cabinet door open, for instance a
computer or terminal; static discharge may cause damage to
unprotected inputs.
M
OTOR
C
ABLING
In order to prevent electrical cross-talk, motor cables not
incorporating a braided screen shield must remain within
earthed metal conduit the entire exposed length of travel. It is
advised that each high power motor cable utilize its own
conduit.
F
ERRITE
A
BSORBER
S
PECIFICATIONS
The absorbers described in these installation recommenda-
tions are made from a low-grade ferrite material which has
high losses at radio frequencies. They therefore act as a lossy
element in this waveband.
The recommended components are produced by Parker
Chomerics (617-935-4850) and are suitable for use with cable