User Manual Owner's manual

Rockwell Automation Publication 280E-UM001B-EN-P - July 2012 47
Installation and Wiring Chapter 2
• Using an EMI filter, with any drive rating, may result in relatively high
ground leakage currents. Therefore, the filter must only be used in
installations that are solidly grounded (bonded) to the building power
distribution ground. Grounding must not rely on flexible cables and
should not include any form of plug or socket that would permit
inadvertent disconnection. Some local codes may require redundant
ground connections. The integrity of all connections should be
periodically checked.
Wiring
Wire in an industrial control application can be divided into three groups: power,
control, and signal. The following recommendations for physical separation
between these groups is provided to reduce the coupling effect:
• Minimum spacing between different wire groups in the same tray should
be 6 in. (16 cm).
• Wire runs outside an enclosure should be run in conduit or have shielding/
armor with equivalent attenuation.
• Different wire groups should be run in separate conduits.
• Minimum spacing between conduits containing different wire groups
should be 3 in. (8 cm).
Grounding
An effectively grounded product is one that is “intentionally connected to earth
through a ground connection or connections of sufficiently low impedance and
having sufficient current-carrying capacity to prevent the buildup of voltages
which may result in undue hazard to connected equipment or to persons” (as
defined by the US National Electric Code NFPA70, Article 100B). Grounding
is done for two basic reasons: safety (defined above) and noise containment or
reduction. While the safety ground scheme and the noise current return circuit
may sometimes share the same path and components, they should be considered
different circuits with different requirements.
Grounding Safety Grounds
The object of safety grounding is to ensure that all metalwork is at the same
ground (or Earth) potential at power frequencies. Impedance between the drive
and the building scheme ground must conform to the requirements of national
and local industrial safety regulations or electrical codes. These will vary based
on country, type of distribution system and other factors. Periodically check the
integrity of all ground connections.