Guidelines for planning the electrical installation 55
Recommended power cable types
Power cable types for limited use
Not allowed power cable types
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 on page 53,
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.
Symmetrical shielded cable with three phase conductors and a concentric PE
conductor as shield. The shield must meet the requirements of IEC 61439-1,
see section Motor cable shield on page 53. Check with local / state / country
electrical codes for allowance.
Symmetrical shielded cable with three phase conductors and a concentric PE
conductor as shield. A separate PE conductor is required if the shield does not
meet the requirements of IEC 61439-1, see section Motor cable shield on page
53.
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 section Motor cable shield on page 53.
A four-conductor system (three phase conductors and a protective conductor on
a cable tray) is not allowed for motor cabling (allowed for input cabling).
Symmetrical shielded cable with individual shields for each phase conductor is
not allowed on any cable size for input and motor cabling.
1 Insulation jacket
2 Helix of copper tape or copper wire
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