VLT
®
FCD Series
■
Use of EMC compliant cables
In order to comply with requirements for EMC immu-
nity of the control cables and EMC emissions from
the motor cables screened/armoured cables must be
used.
The ability of a cable to reduce the amount of ingo-
ing and outgoing radiation of electric noise depends
on the transfer impedance (Z
T
). The screen of a ca-
ble 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 as-
sessing 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 ca-
ble 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.
MG.04.A1.02 - VLT is a registered Danfoss trade mark
35
Installation
