VLT
®
5000 FLUX
■
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 transfer
impedance (Z
T
). The screen of a cable is normally
designed to reduce the transfer of electric noise;
however, a screen with a lower transfer impedance
(Z
T
) value is more effective than a screen with a
higher transfer impedance (Z
T
).
Transfer impedance (Z
T
) is rarely stated by
cable manufacturers, but it is often possible to
estimate transfer impedance (Z
T
) by assessing
the physical design of the cable.
Transfer impedance (Z
T
) can be assessed on the
basis of the following factors:
-
The conductibility of the screen material.
-
The contact resistance between the individual
screen conductors.
-
The screen coverage, i.e. the physical area
of the cable covered by the screen - often
stated as a percentage value.
-
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
percentage screen coverage.
This is the typical Danfoss reference cable.
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.
MG.55.A6.02 - VLT is a registered Danfoss trademark
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