Notes on project planning
Discharge current for mobile systems
5.2
5.2.5

5.2−3
EDSVF9383V EN 7.1−04/2012
5.2.5 Discharge current for mobile systems
Frequency inverters with internal or external RFI filters usually have a
discharge current to PE potential that is higher than 3.5 mA AC or 10 mA DC.
Therefore, fixed installation as protection is required (see EN 61800−5−1).
This must be indicated in the operational documents.
If a fixed installation is not possible for a mobile consumer although the
discharge current to PE potential is higher than 3.5 mA AC or 10 mA DC, an
additional two−winding transformer (isolating transformer) can be included
in the current supply as a suitable countermeasure. Here, the PE conductor
is connected to the PEs of the drive (filter, inverter, motor, shieldings) and
also to one of the poles of the secondary winding of the isolating
transformer.
Devices with a three−phase supply must have a corresponding isolating
transformer with a secondary star connection, the star point being
connected to the PE conductor.
prim.
sec.
L1
N
PE
L1L1 LL2
N1 NN2
U
V
W
filter inverter
M
3~
8200vec017
Fig. 5.2−1 Installation of a two−winding transformer (isolating transformer)
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