Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 74)

Publication GMC-RM001A-EN-P — July 2001
8-2 Motor Wiring
Shielding Motor Power
Cables The benefits of using shielded cable are listed below (also refer to
Figure 8.2).
• The shield strongly attenuates the electric field (E field) noise.
• Core to shield capacitance is added to the stray capacitance at A &
C increasing ground currents in the loop A, C, D, E, and F.
• These currents generate a magnetic field (H field).
It is important to minimize the area of this loop as far as possible by
routing the cable close to grounded metalwork.
Figure 8.2
Shielded motor power cable
Grounding Motor Power
Cable Shields Observe the following guidelines when bonding the motor power
cable shield to ground. Bond motor power cable shields:
• At the motor frame.
• To the panel at entry to the cabinet (optional).
• To the drive (amplifier) chassis. If a connection point is not
provided, bond to the adjacent panel.
These connections must be made at the circular section, not by
creating pigtails. Refer to the section Grounding Cable Shields in
Appendix A for examples of grounding at the circular section.
Cable shield
grounded both
ends
Heatsink
(connected to
chassis)
Cable shield
introduces more stray
capacitance to ground
A C
DC+
DC-
Panel Machine Structure
Windings
F
D
E
Drive Motor