Transmitter
96 97
99
98
91 92 93 95
50
12
L1 L2
L1
PE
L3
W PE
V
U
F1
L2
L3
N
PE
130BA175.12
18
53
37
55
54
M
3
5 kΩ
Illustration 6.63 Electrical Connection Diagram
6.8.2 Use of EMC-Correct Cables
Danfoss recommends braided screened/armoured cables 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 transfer
impedance (Z
T
). The screen of a cable is normally designed
to reduce the transfer of electric noise; however, a screen
with a lower transfer impedance (Z
T
) value is more
effective than a screen with a higher transfer impedance
(Z
T
).
Transfer impedance (Z
T
) is rarely stated by cable manufac-
turers, but it is often possible to estimate transfer
impedance (Z
T
) by assessing the physical design of the
cable.
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 1.1 mm 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
Illustration 6.64 Transfer Impedance
Electrical Installation
Design Guide
118
Danfoss A/S © Rev. 06/2014 All rights reserved.
MG11BC02
6
6
