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Let-through current curve


With very high currents, the fusible elements of the fuse links melt so quickly that the peak short-circuit current Ip can no longer occur.
The highest instantaneous value which is reached by the current during the breaking process is referred to as the maximum let-through current.
The limited currents are indicated on so-called peak let-through current charts.
They start at the root-mean-square value of the solid short-circuit current Irms, at which the rated-current line In intersects the line of the unlimited peak short-circuit current Ic (figure below).

NEOZED let-through current chart.jpg

NEOZED let-through current chart (SOURCE: Siemens)