Recommended power cable types
Symmetrical shielded cable with three phase conductors and a concentric PE conductor
as the shield. The shield must meet the requirements of IEC 61439-1, see General
rules (page 52). Check with local/state/country electrical codes for allowance.
Symmetrical shielded cable with three phase conductors and a concentric PE conductor
as the shield. A separate PE conductor is required if the shield does not meet the re-
quirements of IEC 61439-1, see General rules (page 52).
Symmetrical shielded cable with three phase conductors and symmetrically constructed
PE conductor, and a shield. The PE conductor must meet the requirements of IEC
61439-1, see General rules (page 52).
Power cable types for limited use
A four-conductor system (three phase conductors and a protective conductor on a cable
tray) is not allowed for motor cabling (it is allowed for input cabling).
A four-conductor system (three phase conductors and a PE conductor in a PVC conduit)
is allowed for input cabling with phase conductor cross-section less than 10 mm
2
(8 AWG) or motors ≤ 30 kW (40 hp). Not allowed in the USA.
Corrugated or EMT cable with three phase conductors and a protective conductor is
allowed for motor cabling with phase conductor cross section less than 10 mm
2
(8 AWG)
or motors ≤ 30 kW (40 hp).
Not allowed power cable types
Symmetrical shielded cable with individual shields for each phase conductor is not allowed
on any cable size for input or motor cabling.
ï¿ Motor cable shield
If the motor cable shield is used as the sole protective earth conductor of the motor, make
sure that the conductivity of the shield is sufficient. See section General rules (page 52)
above, or IEC 61439-1.
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.
54 Planning the electrical installation
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