Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 73)

Publication GMC-RM001A-EN-P — July 2001
Chapter
8
Motor Wiring
Chapter Objectives This chapter describes shielding, grounding, and splicing techniques
for use with motor wiring. This chapter covers the following topics:
• Understanding noise in motor power wiring
• Shielding motor power cables
• Grounding motor power cable shields
• Applying ferrite sleeves
• Splicing motor power cables
• Handling excess cable
• Installing long motor cables
Understanding Noise in
Motor Power Wiring The PWM Drive to motor power conductors are typically the most
intense noise source in a system. Proper implementation of shielding,
grounding, splicing, and treatment of excess cable is essential to
reducing noise in your system. In the figure below:
• The unshielded conductors radiate an electric noise field that
couples capacitively with adjacent wiring.
• Stray capacitance at A & C cause ground currents to flow creating
a magnetic noise field that couples inductively with adjacent
wiring.
Figure 8.1
Motor power cable noise
Radiation by E (electric) field
Unshielded motor cable
both conducts and
radiates noise
Heatsink
(connected
to chassis)
Radiation by
H (magnetic)
field from this
loop
Drive Motor
A
C
DC+
DC-
Panel Machine Structure
Windings