Planning the electrical installation 63Additional note for sine filtersSine filters protect the motor insulation system. Therefore, du/dt filter can be replacedwith a sine filter. The peak phase-to-phase voltage with the sine filter is approximately1.5 · UN.Selecting the power cables General rulesSelect the input power and motor cables according to local regulations:• Select a cable capable of carrying the drive nominal current. See section Ratings(page 137) for the rated currents.• Select a cable rated for at least 70 °C maximum permissible temperature ofconductor in continuous use. For US, see Additional US requirements, page 68.• The inductance and impedance of the PE conductor/cable (grounding wire) mustbe rated according to permissible touch voltage appearing under fault conditions(so that the fault point voltage will not rise excessively when a ground faultoccurs).• 600 V AC cable is accepted for up to 500 V AC. 750 V AC cable is accepted forup to 600 V AC. For 690 V AC rated equipment, the rated voltage between theconductors of the cable should be at least 1 kV.Use symmetrical shielded motor cable (see page 66) for drive frame size R5 andlarger, or motors larger than 30 kW (40 hp). A four-conductor system can be used upto frame size R4 with up to 30 kW (40 hp) motors, but shielded symmetrical motorcable is always recommended. Ground motor cable shields 360° at both ends. Keepthe motor cable and its PE pigtail (twisted shield) as short as possible to reduce high-frequency electromagnetic emissions.Note: When continuous metal conduit is employed, shielded cable is not required.The conduit must have bonding at both ends.A four-conductor system is allowed for input cabling, but shielded symmetrical cableis recommended.Compared to a four-conductor system, the use of symmetrical shielded cable reduceselectromagnetic emission of the whole drive system as well as the stress on motorinsulation, bearing currents and wear.The protective conductor must always have an adequate conductivity. The tablebelow shows the minimum cross-sectional area related to the phase conductor sizeaccording to IEC 61439-1 when the phase conductor and the protective conductorare made of the same metal.
