Page 208 - Ferraz semiconductor DIN

Semiconductor fuses
Semiconductor (AC) fuses

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

Cut-off characteristics Size 71
Time-current characteristics
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
Curves indicating pre-arcing time for each rated cur-
rent as a function of RMS value of pre-arcing current
I. Size
- Tolerances on this current ± 8 %. 71
- 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 according 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
Horizontal curves indicating the maximum values
of total operating I t (I t ) as function of the
2
2
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
136 12/04