Rockwell Automation 7000L PowerFlex 7000 Medium Voltage AC Drive C Frame - Marine - Manual (Page 92)

2-62 Drive Installation
7000L-UM302B-EN-P – June 2013 7000 “C” Frame - Marine
Grounding Practices
The purpose of grounding is to:
• provide for the safety of personnel
• limit dangerous voltages on exposed parts with respect to ground
• facilitate proper overcurrent device operation under ground fault
conditions, and
• provide for electrical interference suppression
I M P O R T A N T I M P O R T A N T Generally, the means used for external grounding
of equipment should be in accordance with the
Canadian Electrical Code (CEC), C22.1 or the
National Electrical Code (NEC), NFPA 70 and
applicable local codes.
Refer to the grounding diagrams that follow for ground connections.
The drive‟s main ground bus must be connected to the system
ground. This ground bus is the common ground point for all grounds
internal to the drive.
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
Figure 2.66 – Ground Connection Diagram with Isolation Transformer
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
FILTER
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
FILTER
Figure 2.67 – Ground Connection Diagram with Line Reactor
Each power feeder from the substation transformer to the drive must
be provided with properly sized ground cables. Utilizing the conduit
or cable armor as a ground on its own is not adequate.