Danfoss VLT DMS 300 Manual page 76

Use of EMC compliant cables
In order to comply with requirements for EMC immunity
of the control cables and EMC emissions from the
motor cables shielded/armoured cables must be used.
The ability of a cable to reduce the amount of ingoing
and outgoing radiation of electric noise depends
on the transfer impedance (Z
cable is normally designed to reduce the transfer of
electric noise, and a shield with a lower Z
effective than a shield with a higher Z
Z is rarely stated by cable manufacturers, but it
T
is often possible to estimate Z
assessing the physical design of the cable.
76
). The shield of a
T
is more
T
.
T
by looking at and
T
Decentral Solutions
Z can be assessed on the basis of the following factors:
T
- the contact resistance between the individual
shield conductors.
- Shield coverage, i.e. the physical area of the
cable covered by the shield. Is often stated as a
percentage and should be no less than 85%.
- The shield type, i.e. braided or twisted pattern. A
braided pattern or closed pipe is recommended.
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