Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 58)

58 Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014
Chapter 4 Best Practices
In an industrial control cabinet, the equivalent to the copper ground layer of a
printed circuit board (PCB) is the mounting panel. A panel made of zinc-plated,
mild steel functions well as a ground plane. If painted, remove the paint at each
mounting and grounding point.
Zinc-plated steel is strongly recommended due to its ability to bond with the
drive chassis and resist corrosion. The disadvantage with painted panels, apart
from the cost in labor to remove the paint, is the difficulty in making quality
control checks to verify if the paint has been properly removed, and any future
corrosion of the unprotected mild steel can compromise noise performance.
Plain stainless steel panels are also acceptable but are inferior to zinc-plated mild
steel due to their higher ohms-per-square resistance.
Though not always applicable, a plated cabinet frame is also highly desirable
because it makes a high frequency bond between panel and cabinet sections more
reliable.
Doors
For doors 2 m (78 in.) in height, ground the door to the cabinet with two or three
braided straps.
EMC seals are not normally required for industrial systems.
EMC Specific Installations
A steel enclosure is recommended to help guard against radiated noise to meet
EMC standards. If the enclosure door has a viewing window, a laminated screen
or a conductive optical substrate can block EMC.
Do not rely on the hinge for electrical contact between the door and the
enclosure. Install a grounding wire. For doors 2 m (78 in.) in height, use two or
three braided grounding straps between the door and the cabinet. EMC gaskets
are not normally required for industrial systems.
Layout
Plan the cabinet layout so that drives are separated from sensitive equipment.
Choose conduit entry points that allow any common mode noise to remain away
from programmable logic controllers (PLCs) and other equipment that can be
susceptible to noise. Refer to
Moisture on page 72 for additional information.