Use Of Emc-Correct Cables - Danfoss VLT 6000 HVAC Series Design Manual

Use of EMC-correct cables

Braided screened/armoured cables are recommended
to optimise EMC immunity of the control cables and
the EMC emission from the motor cables.
The ability of a cable to reduce the in- and outgoing
radiation of electric noise depends on the switching
impedance (Z ). The screen of a cable is normally de-
T
signed to reduce the transfer of electric noise; howev-
er, a screen with a lower Z
a screen with a higher Z .
T
Z is rarely stated by cable manufacturers, but it is of-
T
ten possible to estimate Z
design.
76
value is more effective than
T
by assessing the physical
T
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VLT 6000 HVAC Series
Z can be assessed on the basis of the following fac-
T
tors:
- The contact resistance between the individ-
ual screen conductors.
The screen coverage, i.e. the physical area
-
of the cable covered by the screen - often
stated as a percentage value. Should be min.
85%.
- Screen type, i.e. braided or twisted pattern.
Aluminium-clad with copper wire.
Twisted copper wire or armoured steel wire cable.
Single-layer braided copper wire with varying per-
centage screen coverage.
Double-layer braided copper wire.
Twin layer of braided copper wire with a magnetic,
screened/armoured intermediate layer.
Cable that runs in copper tube or steel tube.
Lead cable with 1.1 mm wall thickness with full cov-
erage.
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MG.61.B5.02 - VLT is a registered Danfoss trademark