Rockwell Automation 1391 USER MNL/DIGITAL AC SERVO DR - Manual (Page 64)

Chapter 7
Installation
7-3
Wiring Recommendations General Information
The information supplied in this manual on wire sizes, practices, layouts,
system configurations and grounding/shielding techniques for the
1391-DES Servo Drive are presented as guidelines. Due to the diversity of
applications and systems, no single method of wiring is completely
applicable.
Important: This information represents common PWM servo system
wiring configurations, size and practices that have proven satisfactory in a
majority of applications. The National Electrical Code, local electrical
codes, special operating temperatures, duty cycles or system configurations
will take precedence over the values and methods listed. Refer to Chapter 5
for detailed descriptions of input and output terminations before beginning
the task of wiring.
Wire Sizes
Unless noted, the wire sizes in this manual are recommended minimums
and assume type MTW wire (machine tool wire, 75
°
C, minimum) per
NFPA 79. Since ambient conditions vary widely, on certain applications, a
derating factor has to be taken into account. Also, wiring to drives or
motors exceeding 50 feet (15.2 meters) in length (total includes to and
from device) may cause excessive voltage drops. Consult the National
Electrical (or local) Code for factors on ambient conditions, length etc. or
the Allen-Bradley Sales Representative in your area for further
information.
Shielding
Reasonable care must be taken when connecting and routing power and
signal wiring on a machine or system. Radiated noise from nearby relays
(relay coils should have surge suppressors), transformers, other electronic
drives, etc. may be induced into the velocity command signal lines causing
undesired movement of the servomotor.
To help alleviate the problem, machine power and signal lines must be
routed separately. The 1391-DES power and signal lines must be shielded,
twisted and routed in separate ferrous metal conduit or harnesses spaced at
least 12” (304.8 mm) apart. Power leads are defined here as the transformer
primary and secondary leads, motor leads and any 115V AC or above
control wiring for relays, fans, thermal protectors etc. Signal wiring is
defined as velocity command, resolver feedback, enable lines and low level
logic signal lines.
Feedback, command signal and other shields must be insulated from each
other and connected at a common machine or system earth ground in a
“star” fashion (i.e. all shields connected to a single earth ground point).
This helps to minimize radiated and induced noise problems and ground
loops. Refer to the paragraph entitled “Grounding” and Appendix B.