Datasheet

7
(generally 100,000 times)
②Obtain load ratio from Pulse resistance characteristics.
(Fig. D)
Example : 100,000 times is required against inrush current
applied.
The load ratio is 35% or less from Fig. D.
4–5 Calculation from Joule integral and load ratio
Use Formula 4 to calculate the standard I
2
t for the fuse to be
used.
Standard I
2
t of fuse > (I
2
t of inrush current/load ratio) ..........
..........Formula 4
Example : I
2
t of pulse = 60 A2s,
Pulse applied = 2 ms, Required load ratio = 35%
From Formula 4,
Standard I
2
t of fuse > 60/0.35 = 171.4 (A2s)
The standard I
2
t of the fuse should be 171.4 (A2s) or more.
Since the rush pulse applied is 2 ms, obtain the intersection
of 2 ms (horizontal axis) and 171.4 A2s (vertical axis) from Fig.
E (refer to the arrow shown in Fig. E).
Select a fuse whose curve is above the intersection. Type JHC
with rated current of 50 A and 40A should be selected.
5. Final determination of rated value
Determine the rated current of micro fuse. Rated
current should meet all the calculation results.
Example : Rated current of 50 A and 40A meets the all requirement.
6. Operation check using actual device
After selecting rating, confirm if the device works properly under
pre-determined conditions.
Fig. D
JOULE INTEGRAL VS. FUSING TIME
10
100
1000
10000
100000
1000000
0 10 20 30 40 50 60 70 80 90 100
Load ratio (%)
Number of resistance (cycle)
Fig. E
10
100
1000
10000
100000
1000000
0.001 0.01 0.1 1 10 100
Fusing time (s)
Joule Integral (A
2
s)