ICP-S Technical Manual
Overcurrent Protection Elements
Rev.A
9/13
Joule Integral Calculation of Irregularly Increasing or Decreasing Current
Current mode: Irregular triangular wave form
Model: ICP-S1.0
Wave form:
Wave form approximation: The above wave form is approximated by electrically calculating the Joule
integral of each segment of the current wave form. In consideration of the heat
cycling and mechanical fatigue of the ICP-S, however, a practical Joule
integral value is calculated from an approximation curve obtained by
connecting the peak of each current wave form.
Test: Obtain the approximated value by substituting the values into the formula
(triangular wave form I
2
t = 1/3
•
Im
2
•
t).
I
2
t = 1/3
×
3
2
A
×
1ms = 3 (A
2
•
ms)
Plotting test:
Test results: The steady-state current does not exceed line C. Therefore, it is considered that the ICP-S
will not deteriorate or break the current.
1ms
3A
Actual wave form
Approximation curve for
Joule integral calculation
0.001
0.01
0.1
1
10
100
1000
10000
0.01
Time (msec)
I
2
t (A
2
- ms)
0.1
1
10
100
1000
10000
100000
I
2
t-t
Characteristic Curve (ICP-S1.0)
Graph 2
Ta=25
°
C
A :Effective pulse breaking
line (with no margin)
B: Effective pulse critical line
(with no margin)
C: Effective pulse recommended
critical line (with margin)
3 (A
2
ms) at 1ms
