Metal Conduit; Power Cable Shield; Selecting The Control Cables; Shielding - ABB ACS880 Electrical Planning Instructions

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 NEC 70, 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.
1
1 Insulation jacket
2 Helix of copper tape or copper wire
3 Copper wire shield
4 Inner insulation
5 Cable core

Selecting the control cables

￭

Shielding

Only use shielded control cables.
Use a double-shielded twisted pair cable for analog signals. This type of cable is
recommended for the pulse encoder signals also. Employ one individually shielded pair for
each signal. Do not use common return for different analog signals.
Electrical planning guidelines 23
Notes
Prefer symmetrical shielded VFD cable.
Allowed internally in enclosures when in accordance
with UL.
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