Danfoss VLT 6000 HVAC

VLT
®
6000 HVAC
55MG.60.B1.02 - VLT is a registered Danfoss trade mark
Installation
■■
■■
■ Use of EMC-correct cables
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
value is more
effective than a screen with a higher Z
T
. Z
T
is rarely
stated by cable manufacturers, but it is possible to
estimate Z
T
by looking at the cable and assessing its
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%.
- The screen type, i.e. braided or twisted pattern. A
braided pattern or a closed tube is recommended.
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.