Page 77 - Ferraz semiconductor DIN

Semiconductor fuses
Semiconductor (AC) fuses

Protistor Square-body Fuses
®
PSC aR sizes 3x - 450V to 700 VAC
Curves set

Size 31

Cut-off characteristics
Below, right: Curves indicating for each rated
current the peak value I that the current may
c
reach as a function of the prospective fault
current I .
p

Size Time-current characteristics
31
Above, left: Curves indicating pre-arcing time for
each rated current as a function of RMS value of pre-
arcing current I.
- Tolerances on this current ± 8 %.
- Beyond 30 sec or 10 sec, small overloads must be
eliminated by another device.
- Curve CC’ represents the maximum times taken by
the associated device to clear small overloads; only its
horizontal line is represented. Its oblique line must be
plotted according to sketch, top right corner.
- The intersection of the fuse and CC’ curves
indicates the minimum breaking current Ipm of the
fuse.

Maximum values of total
2
operating I t and total operating
times
Left: Horizontal curves indicating the maximum
values of total operating I t (I t ) as function of the
2
2
t
prospective current I at 660 V, cos ϕ = 0.15.
p
The oblique lines indicate the corresponding total
operating time T , with pre-arcing time in brackets.
t
SCAC86 12/04