Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 71)

Chapter 4
Installation
4-6
Grounding Procedures The purpose of grounding is to:
•
Limit dangerous voltages on exposed parts to ground potential in the
event of an electrical fault.
•
To facilitate proper overcurrent device operation when ground fault
conditions are incurred.
•
To provide for electrical interference suppression.
The general grounding concept for the 1395 is shown in Figure 4.3 and
explained below.
Safety Ground (PE) – is the safety ground required by code. The ground
bus can be connected to adjacent building steel (girder, joist) or a floor
ground loop, provided grounding points comply with NEC regulations.
Multiple connections are permitted, but Do Not ground at the same point as
the Signal Ground (TE). The minimum distance between Signal and
Safety Ground is 10 feet (3 meters). The ground bus requires a maximum
of 1 ohm resistance to ground.
Power Feeder – Each power feeder from the substation transformer to the
drive must be provided with properly sized ground cables. Simply utilizing
the conduit or cable armor as a ground is not adequate. The conduit or
cable armor and ground wires should be bonded to substation ground at
both ends. Each transformer enclosure and/or frame must be bonded to
ground at a minimum of two locations.
Motor Connection – Each DC motor frame must be bonded to grounded
building steel within 20 feet (6 meters) of its location and tied to the drives
PE via ground wires within the power cables and/or conduit. Bond the
conduit or cable armor to ground at both ends. The ground wire size and
installation must be per NEC Article 250.
Signal Ground (TE) – must be connected to an earth ground by a
continuous separate lead (insulated #6 AWG or larger).
The PLC I/O Communication Link must be run in grounded steel conduit.
The conduit should be bonded to ground at both ends. Ground the cable
shield at the drive end only.
Encoder Connections – if required, must be routed in grounded steel
conduit. The conduit must be grounded at both ends. Ground the cable
shield at the motor only.
Tachometer Connections – if required, must be routed in grounded steel
conduit. The conduit must be grounded at both ends. Ground the cable
shield at the drive end Only.
Refer to the auxiliary device instruction manual for special grounding
recommendations.