5.7.2. 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 manufacturers 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 cov-
erage.
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 thick-
ness.
5. How to Install
VLT
®
HVAC Drive Design Guide
108
MG.11.B2.02 - VLT
®
is a registered Danfoss trademark
5
Содержание VLT series
Страница 78: ...4 How to Order VLT HVAC Drive Design Guide 78 MG 11 B2 02 VLT is a registered Danfoss trademark 4...
Страница 120: ...7 RS 485 Installation and Set up VLT HVAC Drive Design Guide 120 MG 11 B2 02 VLT is a registered Danfoss trademark 7...
Страница 152: ...8 Troubleshooting VLT HVAC Drive Design Guide 152 MG 11 B2 02 VLT is a registered Danfoss trademark 8...