Symmetrical shielded cable reduces electromagnetic emission of the whole drive system
as well as the stress on motor insulation, bearing currents and wear.
Metal conduit reduces electromagnetic emission of the whole drive system.
The protective conductor must always have an adequate conductivity.
Unless local wiring regulations state otherwise, the cross-sectional area of the protective
conductor must agree with the conditions that require automatic disconnection of the
supply required in 411.3.2. of IEC 60364-4-41:2005 and be capable of withstanding the
prospective fault current during the disconnection time of the protective device. The
cross-sectional area of the protective conductor can either be selected from the table
below or calculated according to 543.1 of IEC 60364-5-54.
This table shows the minimum cross-sectional area of the protective conductor related
to the phase conductor size according to IEC/UL 61800-5-1 when the phase conductor
and the protective conductor are made of the same metal. If this is not so, the
cross-sectional area of the protective grounding conductor shall be determined in a
manner which produces a conductance equivalent to that which results from the
application of this table.
Minimum cross-sectional area of the corres-
ponding protective conductor
S
p
(mm
2
)
Cross-sectional area of the phase conduct-
ors
S (mm
2
)
S
1)
S ≤ 16
1616 < S ≤ 35
S/235 < S
1)
To comply with standard IEC/EN 61800-5-1 (UL 61800-5-1)
• use a protective earth conductor with a minimum cross-sectional area of 10 mm
2
Cu or 16 mm
2
Al (as an
alternative when aluminum cables are permitted),
or
• use a second protective earth conductor of the same cross-sectional area as the original protective earth
conductor,
or
• use a device that automatically disconnects the supply if the protective earth conductor is damaged.
If the protective earth conductor is separate (that is, it does not form part of the input power cable or the input
power cable enclosure), the minimum cross-sectional area must be:
• 2.5 mm
2
when the conductor is mechanically protected,
or
• 4 mm
2
when the conductor is not mechanically protected.
￭ Typical power cable sizes
See the technical data.
70 Guidelines for planning the electrical installation
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