Kruger Ecowatt K320 Series Operation Manual page 355

Ecowatt Drive K320 series
®
D.4 Cables
D.4.1 Power cables
The sizes of the input power cables and motor cables must meet the local regulation.
The input power cables and motor cables must be able to carry the corresponding load

currents.
The maximum temperature margin of the motor cables in continuous operation cannot be

lower than 70°C.
The conductivity of the PE grounding conductor is the same as that of the phase

conductor, that is, the cross-sectional areas are the same.
For details about the EMC requirements, see Appendix B Technical data

To meet the EMC requirements stipulated in the CE standards, you must use symmetrical
shielded cables as motor cables (as shown in the following figure).
Four-core cables can be used as input cables, but symmetrical shielded cables are
recommended. Compared with four-core cables, symmetrical shielded cables can reduce
electromagnetic radiation as well as the current and loss of the motor cables.
Note: If the conductivity of the shield layer of the motor cables cannot meet the requirements,
separate PE conductors must be used.
To protect the conductors, the cross-sectional area of the shielded cables must be the same as
that of the phase conductors if the cable and conductor are made of materials of the same type.
This reduces grounding resistance, and thus improves impedance continuity.
To effectively restrict the emission and conduction of radio frequency (RF) interference, the
conductivity of the shielded cable must at least be 1/10 of the conductivity of the phase
conductor. This requirement can be well met by a copper or aluminum shield layer. The
following figure shows the minimum requirement on motor cables of a VFD. The cable must
consist of a layer of spiral-shaped copper strips. The denser the shield layer is, the more
effectively the electromagnetic interference is restricted.
Symmetrical shielded cable
PE conductor and
shield layer
Conductor
Jacket
PE
Insulator
Optional peripheral accessories
Shield layer
Conductor
Jacket
Insulator
-346-
-
Four-core cable
Conductor
Jacket
PE
Insulator