Rockwell Automation 1397 DC Drive Firmware 2.xx - Manual (Page 26)

2–8 Installation
Publication 1397-5.0 — June, 2001
The purpose of grounding is to:
•
Limit dangerous voltages to ground potential on exposed parts in
the event of an electrical fault.
•
To facilitate proper operation of overcurrent device when ground
fault conditions are incurred.
•
To provide suppression of electrical interference.
The general grounding concept for the 1397 is shown in Figure 2.6
and explained below. Specific Drive ground point locations are
detailed in Figures 2.7, 2.8 and 2.9.
Safety Ground – Is the safety ground required by code. The
ground bus can be connected to adjacent building steel (girder, joist)
or a floor ground grid, provided grounding points comply with NEC
regulations. Multiple connections are permitted, but Do Not ground
at the same point as a Signal Ground. The minimum distance
between Signal and Safety Ground is 10 feet (3 meters). The ground
bus is limited to 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 Safety Ground 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.
Encoder Connections – If used, must be routed in grounded steel
conduit. The conduit must be grounded at both ends. Ground the
cable shield at the motor only (See Figure 2.6).
Tachometer Connections – If used, must be routed in grounded
steel conduit. The conduit must be grounded at both ends. Ground
the cable shield at the Drive end Only (See Figure 2.6).
(CE) Line Filter Connections – For grounding reqirements in CE
compliant applications, refer to page B.8 in this manual.
(CE) AC Line Inductor Connections – For grounding reqirements
in CE compliant applications, refer to page B.8 in this manual.
Grounding Procedures