Siemens SENTRON - Page 48

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Fault locations in section 1 (upstream of the FC)
Line-frequency AC residual currents occur between the RCCB and the frequency
converter (see gure 18). Protection against these purely sinusoidal 50 Hz residual
currents is provided by all RCCBs (types AC, A, F and B). The section at risk is dis-
connected when the tripping value in the range 0.5 to I
Δn
is reached.
Fault locations in section 2 (in the FC)
Practically smooth DC residual currents occur in the frequency converter (be-
tween the input rectier and the output electronics, i.e. in the DC link circuit)
(see gure 19). There is reliable disconnection in the range from 0.5 to 2 2 I
Δn
if a Type B universal current-sensitive RCCB is used.
Notes on installation and use
Figure 18: Residual current waveform at fault location 1
Figure 19: Residual current waveform at fault location 2