51
Figure 22 shows a typical example of the frequency components that can ow
across a fault impedance of 1 kΩ in the area of fault location 3 (see gure 21).
The clock frequency accounts for a smaller percentage of the total residual
current as the motor frequency increases, while the motor frequency accounts
for a correspondingly higher percentage.
This behavior is characteristic of many different frequency converter versions.
Figure 22: Frequency components in the residual current based on the example of
a frequency converter
Frequency with three-phase supply
Residual currents with R =1kΩ
250
200
150
100
50
0
10 20
30
40 50
60
0
r.m.s. value (mA)
Motor frequency (Hz)
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