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.
a.
Aluminium-clad with copper wire.
b.
Twisted copper wire or armoured steel wire cable.
c.
Single-layer braided copper wire with varying
percentage screen coverage.
This is the typical Danfoss reference cable.
d.
Double-layer braided copper wire.
e.
Twin layer of braided copper wire with a
magnetic, screened/armoured intermediate layer.
f.
Cable that runs in copper tube or steel tube.
g.
Lead cable with 1.1mm wall thickness.
175ZA166.13
0,01
0,1
1
10
100 MHz
10ˉ2
10ˉ3
10ˉ1
1
101
102
104
103
105
a
b
c
d
e
f
g
The lo
w
er the Z the bett
er the cable scr
eening per
for
manc
e
Transfer impedance, Z
t
mOhm/m
Electrical Installation
FC 300 Design Guide
MG.33.BD.02 - VLT
®
is a registered Danfoss trademark
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