Metal Conduit; Power Cable Shield - ABB ACS580 Series Hardware Manual

110 Guidelines for planning the electrical installation
Wiring method
2)
Free air
Enclosures, air handlers, etc.
1) Metallic conduit may be used as an additional ground path, provided this path is a solid path capable
of handling ground currents.
2) See NFPA NFPA 70 (NEC), UL, and local codes for your application.
3) Non-metallic conduit use underground is allowed; however, these installations inherently have an
increased chance for nuisance problems due to the potential for water/moisture in the conduit.
Water/moisture in the conduit increases the likelihood of VFD faults or warnings. Proper installation
is required to make sure there is no intrusion of water/moisture.

Metal conduit

Couple separate parts of a metal conduit together: bridge the joints with a ground
conductor bonded to the conduit on each side of the joint. Also bond the conduits
to the drive enclosure and motor frame. Use separate conduits for input power,
motor, brake resistor, and control wiring. Do not run motor wiring from more than
one drive in the same conduit.
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Power cable shield

If the cable shield is used as the sole protective earth (PE) conductor, make sure
that its conductivity agrees with the PE conductor requirements.
To effectively suppress radiated and conducted radio-frequency emissions, the
cable shield conductivity must be at least 1/10 of the phase conductor conductivity.
The requirements are easily met with a copper or aluminum shield. The minimum
requirement of the motor cable shield of the drive is shown below. It consists of
a concentric layer of copper wires with an open helix of copper tape or copper
wire. The better and tighter the shield, the lower the emission level and bearing
currents.
Notes
Prefer symmetrical shielded VFD cable.
Allowed internally in enclosures when in ac-
cordance with UL.