Use Of Emc-Correct Cables; Earthing Of Screened Control Cables - Danfoss VLT AutomationDrive FC 300 Design Manual

Electrical Installation
L1
L2
L3
N
PE
F1
91 92 93 95
L1 L2 L3
U V W PE
96 97 98
7 7
M
3
Illustration 7.57 Electrical Connection Diagram (6-Pulse
Example Shown)

7.8.2 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 cable's ability to reduce the incoming and outgoing
radiation of electric noise depends on the transfer
impedance (Z
reduce the transfer of electric noise; however, a screen
with a lower transfer impedance (Z
effective.
Cable manufacturers rarely state transfer impedance (Z
but it is often possible to estimate transfer impedance (Z
by assessing the physical design of the cable. See
Illustration 7.58.
214
12
37
PE
18
50
53
55
54
99
Transmitter
). The cable's screen is normally designed to
T
) value is the most
T
®
VLT AutomationDrive FC 300 Design Guide 90-1200 kW
Transfer impedance, Z
mOhm/m
10
10
10
10
10
5 kΩ
1
10
10
10
0,01
Illustration 7.58 Transfer Impedance Z

7.8.3 Earthing of Screened Control Cables

Correct Screening
The preferred method is to secure control and serial
communication cables with screening clamps at both ends
to ensure best possible high frequency cable contact.
If the earth potential between the frequency converter and
the PLC is different, electric noise may occur. Solve this
problem by fitting an equalizing cable next to the control
cable. Minimum cable cross section is 16 mm
),
T
)
T
Illustration 7.59 Equalizing Cable next to a Control Cable
1
2
Table 7.72 Legend to Illustration 7.59
MG34S202 - Rev. 2013-08-19
t
0,1 1 10 100 MHz
T
PLC
PE PE
<10 mm
PE PE
1
2
Min. 16 mm 2
Equalizing cable
a
b
c
d
e
f
g
2
.
FC