Rockwell Automation 1395 Digital DC Drive FRN 5-10.10/9.30 - Manual (Page 132)

Chapter 6
Installation
6-8
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 6.4 and
explained below.
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 Zero
Potential Bus (TE). The minimum distance between Ground and Zero
Potential Bus 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.
Zero Potential Bus (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. Connect 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. Connect 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. Connect the cable
shield at the drive end Only.
Refer to the auxiliary device instruction manual for special grounding
recommendations.