2 Engineering
2.3 Cable cross-sections
DC1…20… and DC1…OE1 Variable Frequency Drives
02/20 MN040059EN
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2.2.4 Total Harmonic Distortion (THD)
The THD value (THD = Total Harmonic Distortion) is defined in standard
IEC/EN 61800-3 as the ratio of the rms value of all harmonic components to
the rms value of the fundamental frequency.
2.2.5 Reactive power compensation devices
Compensation on the power supply side is not required for the variable
frequency drives of the DC1 series. From the AC power supply network they
only take on very little reactive power of the fundamental harmonics
(cos
ϕ
~ 0.98).
2.3 Cable cross-sections
The mains cables and motor cables must be sized as required by local
standards and by the load currents that will be involved.
The PE conductor’s cross-sectional area must be the same as the phase
conductors’ cross-sectional area. The connection terminals marked with
must be connected to the earth-current circuit.
If there are leakage currents greater than 3.5 mA, a reinforced earthing (PE)
must be connected, as required by standard EN 61800-5-1. The cable cross-
section must be at least 10 mm
2
, or the earthing system must consist of two
separately connected earthing cables.
￫
In order to reduce the THD value (up to 30%), it is
recommended to use a DX-LN… mains choke
(
Section 2.5, “Mains chokes“, page 43).
￫
In the AC supply systems with non-choked reactive current
compensation devices, current deviations can enable parallel
resonance and undefinable circumstances.
In the project planning for the connection of variable frequency
drives to AC supply systems with undefined circumstances,
consider using mains chokes.
NOTICE
The specified minimum PE conductor cross-sections
(EN 61800-5-1) must be maintained.
￫
c rated operational data“, page 149
provides the leakage currents for the individual models.
￫
Section 3.5, “EMC installation“, page 70 goes over the EMC
requirements for the motor cables.
