High Speed Fuses
General applications
Rated Voltage
The ac voltage rating of Cooper Bussmann
®
fuses is given in
volts rms. Fuses tested to IEC are tested at 10% above their
rated voltage. British Style BS 88 fuses are tested at 5%
above its rated voltage. UL recognition tests are performed
at
the rated voltage.
Rated Current
Rated current is given in amperes rms. Cooper Bussmann
fuses can continuously carry the rated current.
Melting Characteristic
The melting char-
acteristic shows
the virtual melting
time in seconds as
a function of the
prospective current
in amperes rms.
The fuses are spe-
cially constructed
for short-circuit pro-
tection against high
level fault currents.
Loading and opera-
tion of the fuse in
the non-continu-
ous/dashed section
of the melt curve
must be avoided.
The curve can also
be read as the real
melting time as a
function of the
RMS value of the
pre-arc current.
Clearing Integrals
The total clearing I
2
t at
rated voltage and at
power factor of 15% are
given in the electrical
characteristics. For
other voltages, the
clearing I
2
t is found by
multiplying by correction
factor, K, given as a
function of applied work-
ing voltage, Eg, (rms).
1.5
K
1.0
10
4
6
4
2
10
3
6
4
2
10
2
6
4
2
Virtual Pre-Arcing Time In Seconds
10
1
6
4
2
10
0
6
4
2
10
–1
6
4
2
10
–2
6
4
2
10
–3
6
4
2
10
–4
10
1
2
4
6
8 10
2
2
4
6
8 10
3
For other power factor
values, the total clearing
integral can be calculat-
ed as a multiple of the
clearing integrals, the
correction factor K and
the correction factor X.
X
1.0
0.9
0.8
Arc Voltage
This curve gives the
peak arc voltage, U L ,
which may appear
across the fuse during its
operation as a function
of the applied working
voltage, E g , (rms) at a
power factor of 15%.
Power Losses
0.7
0.1
0.2
0.3
0.4
0.5
COS
1.4
1.2 U
L
10
3
9
8
7
6
5
4
3
E
g
200 300
1.0
K
p
0.8
0.6
0.5
0.4
0.3
0.2
400
500
600 660
Prospective Current In Amperes RMS
Watts loss at rated cur-
rent is given in the electri-
cal characteristics. The
curve allows the calcula-
tion of the power losses
at load currents lower
than the rated current.
The correction factor, K p ,
is given as a function of
the RMS load current, Ib ,
in % of the rated current .
Cut-Off Current
0.1
30 40 50
60
70
I
b
80 90 100%
0.5
0.4
0.3
A fuse operation relating to short-circuits only. When a fuse
operates in its current-limiting range, it will clear a short-cir-
cuit in less than
1
⁄
2
cycle. Also, it will limit the instantaneous
peak let-through current to a value substantially less than
that obtainable in the same circuit if that fuse were replaced
with a solid conductor of equal impedance.
10
5
Peak Let-Through Current
0.2
E
g
100 200 300 400 500 600 660
10
4
10
3
A
B
2
≈
10
2
10
2
10
3
10
4
Prospective Current in Amperes RMS
10
5
10
6
A asymmetrical current
B symmetrical current
88
For product data sheets, visit www.cooperbussmann.com/products/datasheet.asp
COOPER [ COOPER BUSSMANN, INC. ]
