Rockwell Automation 7000 PowerFlex Medium Voltage Air-Cooled (B Frame) Installation - ForGe Control - Manual (Page 62)

62 Rockwell Automation Publication 7000-IN007E-EN-P - June 2014
Chapter 3 Drive Installation
Grounding Practices Grounding:
• increases personnel safety
• limits dangerous voltages on exposed parts with respect to ground
• facilitates proper over-current device operation under ground fault
conditions, and
• provides electrical interference suppression
Generally, all external equipment grounding should meet the Canadian Electrical
Code (CEC) C22.1, or the NEC NFPA 70, and applicable local codes.
Refer to the following diagrams for ground connections. Do not connect the
drive’s main ground bus to the system ground. This ground bus is the common
ground point for all grounds internal to the drive.
Figure 54 - Ground connection diagram with isolation transformer
Figure 55 - Ground connection diagram with line reactor
Provide each power feeder from the substation transformer to the drive with
properly sized ground cables. Using conduit or cable armor as a ground on its
own is insufficient. Note that if you use a drive isolation transformer, do not
ground the WYE secondary neutral point.
Bond each AC motor frame to grounded building steel within 6 m (20 ft) of its
location and tie it to the drive's ground bus via ground wires within the power
cables and/or conduit. The conduit or cable armor should bond to ground at
both ends.
ISOLATION
TRANSFORMER AC
MOTOR
U (T1)
V (T2)
W (T3)
2U
2V
2W
GROUND BUS
Connected to the neutral point
of the output capacitor
OUTPUT
GROUND
NETWORK
ISOLATION
TRANSFORMER AC
MOTOR
U (T1)
V (T2)
W (T3)
2U
2V
2W
GROUND BUS
Connected to the neutral point
of the output capacitor
OUTPUT
GROUND
NETWORK
AC
MOTOR
U (T1)
V (T2)
W (T3)
2U
2V
2W
GROUND BUS
AC LINE
REACTOR
TRANSFORMER
Connected to the neutral point
of the output capacitor
GROUND
FILTE R
AC
MOTOR
U (T1)
V (T2)
W (T3)
2U
2V
2W
GROUND BUS
AC LINE
REACTOR
TRANSFORMER
Connected to the neutral point
of the output capacitor
GROUND
FILTE R