5.11.2 Use of EMC-Compliant Cables
Danfoss recommends braided shielded/armored cables to optimize 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 shield of a cable is normally
designed to reduce the transfer of electric noise; however, a shield with a lower transfer impedance (Z
T
) value is more effective than a shield 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 shield material.
- The contact resistance between the individual shield conductors.
- The shield coverage, i.e., the physical area of the cable covered by the shield - often stated as a percentage value.
- Shield type, i.e., braided or twisted pattern.
a. Aluminum-clad with copper wire.
b. Twisted copper wire or armored steel wire cable.
c. Single-layer braided copper wire with varying percentage shield
coverage.
This is the typical Danfoss reference cable.
d. Double-layer braided copper wire.
e. Twin layer of braided copper wire with a magnetic, shielded/
armored intermediate layer.
f. Cable that runs in copper tube or steel tube.
g. Lead cable with 0.43 in [1.1 mm] wall thickness.
5 How to Install VLT
®
AQUA Drive Design Guide
5-56
MG.20.N5.22 - VLT
®
is a registered Danfoss trademark
5
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