VLT® 7000 Booster
Installation
■ 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
T
). The screen of a cable is normally
designed to reduce the transfer of electric noise;
however, a screen with a lower Z
T
valueismore
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 assessing
the physical design.
Z
T
can be assessed on the basis of the following factors:
- 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. 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
percentage 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
coverage.
MG.70.A1.02 - VLT is a registered Danfoss trademark
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General