Use Of Emc-Compatible Cables - Danfoss VLT FC 102 Series Design Manual

Electrical Installation
Figure 6.63 Electrical Connection Diagram

6.8.2 Use of EMC-Compatible 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 ). The shield of a cable is normally designed
T
to reduce the transfer of electric noise; however, a shield
with a lower transfer impedance (Z
effective than a shield with a higher transfer impedance
(Z ).
T
Transfer impedance (Z ) is rarely stated by cable manufac-
T
turers, but it is often possible to estimate transfer
impedance (Z ) by assessing the physical design of the
T
cable.
MG11BC22
Design Guide
) value is more
T
Danfoss A/S © Rev. 06/2014 All rights reserved.
Transfer impedance (Z ) can be assessed on the basis of
T
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 0.043 in [1.1 mm] wall thickness
Figure 6.64 Transfer Impedance
6 6
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