56 Planning the electrical installation
Sine filters
Sine filters protect the motor insulation system. Therefore, du/dt filter can be replaced with a sine filter. The
peak phase-to-phase voltage with the sine filter is approximately 1.5 · U
N
.
Selecting the power cables
General rules
Dimension the input power and motor cables according to local regulations:
• Dimension the cable to carry the drive load current. See chapter Technical data for the
rated currents.
• Select a cable rated for at least 70 °C maximum permissible temperature of conductor
in continuous use. For US, see Additional US requirements, page 58.
• The inductance and impedance of the PE conductor/cable (grounding wire) must be
rated according to permissible touch voltage appearing under fault conditions (so that
the fault point voltage will not rise excessively when a ground fault occurs).
• 600 V AC cable is accepted for up to 500 V AC
Use symmetrical shielded motor cable, see page 58. Ground the shield(s) of motor
cable(s) 360° at both ends.
Note: When continuous metal conduit is employed, shielded cable is not required. The
conduit must have bonding at both ends as with cable shield.
A four-conductor system is allowed for input cabling, but shielded symmetrical cable is
recommended. To operate as a protective conductor, the shield conductivity requirements
according to IEC 60439-1 are shown below when the protective conductor is made of the
same metal as the phase conductors:
Compared to a four-conductor system, the use of symmetrical shielded cable reduces
electromagnetic emission of the whole drive system as well as the stress on motor
insulation, bearing currents and wear.
Keep the motor cable and its PE pigtail (twisted shield) as short as possible to reduce
high-frequency electromagnetic emissions.
Cross-sectional area of the phase
conductors
S (mm
2
)
Minimum cross-sectional area of the
corresponding protective conductor
S
p
(mm
2
)
S <
16 S
16 < S <
35 16
35 < S S/2
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