Danfoss FC 300 Design Manual page 191

FC 300 Design Guide
8.9.2 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
designed to reduce the transfer of electric noise; however, a screen with a lower transfer impedance (Z
higher transfer impedance (Z ).
T
Transfer impedance (Z ) is rarely stated by cable manufacturers but it is often possible to estimate transfer impedance (Z
T
design of the cable.
Transfer impedance (Z ) can be assessed on the basis of the following factors:
T
- 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.
MG.33.BC.02 - VLT ® is a registered Danfoss trademark
8 Electrical Installation
). The screen of a cable is normally
T
) value is more effective than a screen with a
T
) by assessing the physical
T
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