Rockwell Automation 20D DC SCR Precharge Module - Manual (Page 13)

Installation/Wiring 1-3
AC Supply Source
Considerations The DC SCR Precharge Modules are suitable for use on a circuit capable of
delivering a short circuit rating up to a maximum of 65,000 rms
symmetrical amperes.
If a Residual Current Detector (RCD) is used as a system ground fault
monitor, only Type B (adjustable) devices should be used to avoid nuisance
tripping.
For Unbalanced or Ungrounded Distribution Systems where the potential
exists for abnormally high phase-to-ground voltages (in excess of 125% of
nominal) or the supply system is ungrounded, please refer to Wiring and
Grounding Guidelines for Pulse Width Modulated (PWM) AC Drives
(Allen-Bradley Publication No. DRIVES-IN001…).
For Input Power Conditioning information, please refer to Chapter 2 of
Wiring and Grounding Guidelines for Pulse Width Modulated (PWM) AC
Drives (Allen-Bradley Publication No. DRIVES-IN001…).
General Grounding
Requirements The Safety Ground Terminal (PE) must be connected to the building
grounding scheme. Ground impedance must conform to the requirements
of national and local industrial safety regulations and/or electrical codes.
The integrity of all ground connections should be periodically checked.
For installations within a cabinet, a single safety ground point or ground bus
bar connected directly to building steel should be used. All circuits
including the AC input ground conductor should be grounded
independently and directly to this point or bus bar.
Figure 1.3 shows a
typical grounding scheme.
Figure 1.3 Typical Grounding Scheme
Safety Ground Terminal – PE: The DC SCR Precharge Module safety
ground (PE) must be connected to the customer grounding scheme or earth
ground. This is the safety ground for the DC SCR Precharge Module that is
required by code. This point must be connected to adjacent building steel
Input Transformer AC Drive
DC SCR Precharge
Converter
R
+DC
-DC
S
T
U
M
V
W
A
PE
XFMR Enclosure
Connection to Ground Grid,
Girder or Ground Rod
(Building ground Potential)
Connection to Cabinet
Ground Bus
Panel Ground Bus
Drive Enclosure
Motor Frame
Building Ground Potential
B
X0
C
Inverter
AC Motor
PE