3.3.8 Use of EMC Compliant Cables
To comply with requirements for EMC immunity of the control cables and EMC emissions for the motor cables, use
screened/armoured cables.
The ability of a cable to reduce the amount of ingoing and outgoing radiation of electric noise depends on the transfer
impedance (Z
T
). The screen of a cable is normally designed to reduce the transfer of electric noise, and a screen with a
lower Z
T
is more effective than a screen with a higher Z
T
.
Z
T
is rarely stated by cable manufacturers, but it is often possible to estimate Z
T
by looking at and assessing the physical
design of the cable.
Z
T
can be assessed on the basis of the following factors:
•
The contact resistance between the individual screen conductors.
•
Screen coverage, i.e. the physical area of the cable covered by the screen. Is often stated as a percentage and
should be no less than 85%.
•
The screen type, i.e. braided or twisted pattern. A braided pattern or closed pipe is recommended.
Illustration 3.18 Cable Comparison
Installation
Design Guide
42
Danfoss A/S © Rev. May/2014 All rights reserved.
MG27E402
3
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