Surge Tolerant Fuses
2. UL1459/1950
3. GR 1089
Test circuit
Test circuit
t = 1,5 s/5 s/ 30 Min.
R
I
267 µH
D
puls
R
D
68 Ω
+
20 µF
Fuse
Fuse
50 kΩ
R
M
I
= 40 A/7 A/2.2. A
sc
Fig. 4
Test 1:
Pulse current
Generator no load
The fuse in the test current circuit is loaded with a test current
of ISC = 40 A .
The AC 600 V / 50 Hz source voltage is applied for a total
of 1.5 sec.
50%
t1=10µs
Requirement: The fuse shall interrupt the circuit.
t2=1000µs
Test 2:
The fuse in the test current circuit is loaded with a test current
of ISC = 7 A .
Fig. 5
The AC 600 V / 50 Hz source voltage is applied for a total
of 5 sec.
Test:
1. The pulse amplitude (generator no-load) is set to 1000 V
and the pulse shape to 10 µs / 1000 µs.
Requirement: The fuse shall interrupt the circuit.
Test 3
2. The pulse current Ipuls is set to the value Ipuls max. stated in
the data sheet with limiting resistor RD.
The fuse in the test current circuit is loaded with a test current
of ISC = 2,2 A .
3. Test mode: 50 single pulses, at an interval of 60 sec.
alternating polarity.
The AC 600 V / 50Hz source voltage is applied for at least
30 minutes, or until stable thermal conditions are achieved
in the telecom unit or until the fuse interrupts the circuit.
This test is performed together with the equipment in which the
fuse is installed.
Requirement: The fuse shall not interrupt the circuit.
5) Note: With a charge voltage of UC = 1000 V, the standar-
dized pulse generator in Fig. 5 supplies a maximum pulse
current Ipuls = 14 A, providing the current limiting resistor is
RD = 0Ω. The shunt RM for the current monitoring has a very
low resistance and has no notable influence to the current
amplitude. This means that the data sheet current 14 A (5) does
not represent the maximum permissible pulse amplitude of the
fuse in question, but the maximum current amplitude which can
be supplied by the pulse generator. If a max. current higher
than 14 A is to be expected in a circuit, the
I2t- values of the fuse can be calculated using the formula I2t =
0,72 x i2peak x t2, as a good approximation in order that the
selected fuse can accept the expected current pulse without
interrupting the circuit.
Schurter, Inc. • Phone 707-778-6311 • Fax 707-778-6401 • E-mail: info@schurterinc.com • Website http://www.schurterinc.com
161
SCHURTER [ SCHURTER INC. ]
