VLT
®
2800 Series
Installation
■ Use of EMC compliant cables
In order to comply with requirements for EMC immunity
of the control cables and EM C emissions from the
motor cables screened/armoured cables must b e used.
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.
MG.28.E9.02 - VLT is a registered Danfoss trademark
45
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