6-2
Engineering Guide CDA3000
6 Selection of supplementary components
6.1 Line choke
6.1.1 Effect of the line
choke
Based on the example of a 4 kW inverter CDA34.010
A line impedance of 0.6 mH was assumed for the calculation. This
value results from IEC1800-3 para. 6.1.2 (short-circuit current of
system = 250 times fundamental current of load).
A line impedance of 6 mH was assumed for the calculation. This value
results from IEC1800-3 para. 6.1.2 and from the use of a line choke with
4 % short-circuit voltage (U
K
).
Harmonics load
Function Effect
Use of the line choke reduces the
voltage distortion in the system.
The limit values to be observed for
variable-speed electric drives are
laid down in the standards
EN61800-3 and IEC1800-3.
Of course, the line choke also offers
protection against transient system
voltage peaks.
Reduction of voltage distortion
(THD)
1
Reduction of commutation notches
Reduction of the amplitude of the
line charging current
Increase in service life of the DC-
link capacitors
Attenuation of transient voltage
peaks from contaminated systems
1) THD = Total Harmonic Distortion
Harmonic
Percentage
without line
choke
Percentage
with line choke
Amplitude
without line
choke
Amplitude with
line choke
1
(fundamental)
100% 100% 8.58 A 8.31 A
5 76% 30% 6.4 A 2.55 A
7 57% 8.9% 4.9 A 0.74 A
11 21% 6% 1.85 A 0.5 A
13 to 41 36% 10.9% 3.15 A 0.91 A
Table 6.1 Percentage shares of currents due to harmonics based on the
example of a 4 kW inverter CDA34.010
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