To avoid common-mode currents at fundamental and high frequencies at the same time, use multicore symmetric motor cables
with 3 ground conductors with a shield.
Applying common-mode cores
Common-mode cores across motor cable conductors effectively reduce high-frequency motor bearing currents. On motors with a
power rating of approximately 100 kW and onwards, the result of reduction of bearing currents is most evident.
High-frequency common-mode cores may have an oval or round shape and they are easy-to-install components.
Install common-mode cores in a way that only unshielded power cores of the motor cable are wired through the core. The PE and
shielding wires must be placed outside of the core. It is also important that all 3 motor phase wires are wired through the same core.
Otherwise, the cores do not provide the required functionality.
PE
U
V
W
e
3
0
b
d
8
3
9
.1
0
Illustration 18: Installing Common-mode Cores
Depending on the power rating of the drive installation and the quantity of motor cables connected in parallel, several same-size
common-mode cores might be used. In dedicated product manuals, preselection tables advise on the required minimal quantity of
single common-mode cores to install. The number of cores depend on the power rating, the nominal voltage of the drive installa-
tion, and the length of the applied motor cables.
Applying common-mode cores on motor cables connected in parallel
If many motor cables connected in parallel are used and the power wires of all cables cannot be fitted through the common-mode
cores, place the required number of cores on each individual motor cable. This ensures the saturation of the core due to likely un-
equal current sharing between cables. Wire all 3-phase conductors of each cable through 1 set of cores.
AJ300847815559en-000101 / 130R0337 | 33
Danfoss A/S © 2020.09
Product Overview
VLT® AQUA Drive FC 202
Design Guide