Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 53)

Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014 53
Grounding Chapter 3
Figure 18 - Fully Grounded Scheme
The installation and grounding practices to reduce common mode noise issues
can be categorized into three ratings. The scheme used must consider additional
costs against the operating integrity of all scheme components. If no sensitive
equipment is present and noise is not an issue, the added cost of shielded cable
and other components is not always justified.
Acceptable Grounding Practices
The scheme shown below is an acceptable ground layout for a single drive
installation. However, conduit does not offer the lowest impedance path for any
high frequency noise. If the conduit is mounted so that it contacts the building
steel, it is likely that the building steel offers a lower impedance path and causes
noise to inhabit the ground grid.
Earth Ground Potential
X0
R
S
T
U
V
W
PE PE
A
B
C
PE
Input Transformer AC Drive Conduit
Motor Frame
Motor
Connection to Drive
Structure or Optional
Cabinet Via Conduit
Connector
Strap
Incidental Contact
of Conduit Strap
Motor Frame
Ground
Connection to Ground Grid,
Girder, or Ground Rod
Connection to Cabinet Ground Bus
or Directly to Drive PE Terminal
Panel Ground Bus
Optional Enclosure
Building Ground Potential