Danfoss VLT 8000 AQUA Guide d'installation télécharger pdf (Page 22)

VLT® 8000 AQUA

■ Use of EMC-correct cables

Braided shielded/armored cables are recommended

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

). The shield of a cable is normally

designed to reduce the transfer of electric noise;

however, a schield with a lower transfer impedance

) value is more effective than a shield with a

higher transfer impedance (Z

Transfer impedance (Z

) is rarely stated by

cable manufacturers, but it is often possible to

estimate transfer impedance (Z

) by assessing

the physical design of the cable.

Transfer impedance (Z

) 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.

Aluminium-clad with copper wire.

Twistedcopperwireorarmouredsteelwirecable.

Single-layer braided copper wire with varying

percentage shield coverage.

This is the typical Danfoss reference cable.

Double-layer braided copper wire.

Twin layer of braided copper wire with a magnetic,

shielded/armored intermediate layer.

Cable that runs in copper tube or steel tube.

Lead cable with 1.1 mm wall thickness.

MG.80.A6.22 - VLT is a registered Danfoss trademark

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Danfoss VLT 8000 AQUA Guide d'installation Page 22