Page 224 - Ferraz semiconductor DIN

Semiconductor fuses
Semiconductor (AC) fuses

Protistor Square-body Fuses
®
PSC aR sizes 7x - 650 V to 1300 VAC
Curves set

Time-current characteristics
Size 72

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

Time-current characteristics

Above, left: Curves indicating pre-arcing time for Size
each rated current as a function of RMS value of pre- 72
arcing current I.
- Tolerances on this current ± 8 %.
- Beyond 30 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 accord-
ing to sketch, top right corner.
- The intersection of the fuse and CC’ curves indicates
the minimum breaking current I pm of the fuse.

Maximum values of total operating
I t and total operating times
2
Left: Horizontal curves indicating the maximum
2
2
values of total operating I t (I t ) as function of the
t
prospective current I at 1000V or 850 V(*),
p
cos ϕ = 0.15.
The oblique lines indicate the corresponding total
operating time T , with pre-arcing time in brackets.
t
SCAC137
12/04