High Speed Fuses
General applications
X
Rated Voltage
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.
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.
1.0
0.9
0.8
0.7
Rated Current
Rated current is given in amperes rms. Cooper Bussmann
fuses can continuously carry the rated current.
Melting Characteristic
Arc Voltage
104
The melting char-
0.1
0.2
0.3
0.4
0.5
6
COS
4
acteristic shows
the virtual melting
time in seconds as
a function of the
prospective current
in amperes rms.
This curve gives the
2
1.4
1.2
103
9
peak arc voltage, U ,
103
L
UL
6
4
which may appear
across the fuse during its
operation as a function
of the applied working
2
102
8
7
6
4
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
2
6
5
voltage, E , (rms) at a
101
100
g
6
4
power factor of 15%.
4
3
2
Power Losses
Eg
6
4
200 300 400
500 600 660
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 ,
is given as a function of
the RMS load current, I ,
in % of the rated current.
2
10–1
1.0
0.8
6
4
Kp
2
0.6
0.5
10–2
6
4
0.4
0.3
2
10–3
6
4
0.2
p
2
10–4
101
2
4
6
8
102
Prospective Current In Amperes RMS
2
4
6
8
103
RMS value of the
pre-arc current.
b
Ib
80 90 100%
0.1
30 40 50 60
70
Cut-Off Current
Clearing Integrals
1.5
2
A fuse operation relating to short-circuits only. When a fuse
The total clearing I t at
K
operates in its current-limiting range, it will clear a short-cir-
rated voltage and at
1.0
1
cuit in less than ⁄
2
cycle. Also, it will limit the instantaneous
power factor of 15% are
given in the electrical
characteristics. For
other voltages, the
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.
0.5
0.4
2
clearing I t is found by
105
0.3
multiplying by correction
factor, K, given as a
function of applied work-
0.2
104
Eg
100 200 300 400 500 600 660
ing voltage, E , (rms).
g
103
A
B
2
≈
102
102
103
104
105
106
Prospective Current in Amperes RMS
A asymmetrical current
B symmetrical current
For product data sheets, visit www.cooperbussmann.com/products/datasheet.asp
88
COOPER [ COOPER BUSSMANN, INC. ]
