Siemens SINAMICS G120 Hardware Installation Manual page 25

TT Power System
L1
L2
L3
N
Figure 4-5
A TT power system has one point directly grounded, the exposed conductive parts of the
installation being connected to a ground, which is electrically independent of the ground of
the power system.
IT Power System
L1
L2
L3
N
Figure 4-6
An IT power system has no direct connection to ground - instead the exposed parts of the
electrical installation are grounded.
It will be necessary to provide a mechanism for disconnecting the "DC link midpoint to
ground" capacitor.
Note
TT-/IT power systems can only be used with unfiltered drives.
Power Modules PM240
Hardware Installation Manual, 2006-04-04, A5E00807525B AA
L1 L2 L3
Exposed Conductive Parts
TT power system
L1 L2 L3
Exposed Conductive Parts
IT power system
PE
PE
Installing/Mounting
4.2 Electrical Installation
4-7