ICP-S Technical Manual
Overcurrent Protection Elements
Rev.A
10/13
Joule Integral Calculation of Irregularly Increasing or Decreasing Current
Current mode: Irregular wave form + triangular wave form
Model: ICP-S1.2
Wave form:
Wave form approximation: The above wave form (electric charge wave form) is approximated as an
irregular wave form to calculate the Joule integral of the wave form.
Test:
Plotting test:
Test results: The steady-state current is between lines B and A. Therefore, it is considered that the
ICP-S will deteriorate or break the current due to the repetitive pulses.
Actual wave form
Approximation curve for Joule
integral calculation
10A
8A
6A
2A
3.5A
0.1ms
0.35ms
0.25ms
0.55ms
0.06ms
Item
Peak
current
Im
(A)
t
(ms)
(ms)
(A
2
•
ms)
Formula
Coefficient
×
Im
2
×
t A
2
•
ms)
No.
1
10
0.06
0.06
4.88
9.81
17.88
19.81
20.54
4.88
10
×
8
×
0.06+1/3
×
(10
−
8)
2
×
0.06=
8
×
6
×
0.1+1/3
×
(8
−
6)
2
×
0.1=
6
×
3.5
×
0.35+1/3
×
(6
−
3.5)
2
×
0.35=
3.5
×
2
×
0.25+1/3
×
(3.5
−
2)
2
×
0.25=
1/3
×
(2)
2
×
0.55=
4.93
8.07
1.93
0.73
0.16
0.51
0.76
1.31
0.1
0.35
0.25
0.55
8
6
3.5
2
2
3
4
5
Segmented
period
Lapsed
time
Joule integral
Accumu-
lation
1
3
2
4
5
0.001
0.1
1
10
100
1000
10000
100000
0.01
I
2
t (A
2
- ms)
0.1
1
10
100
1000
10000
100000
Time (msec)
I
2
t-t Characteristic Curve
(ICP-S1.2)
Ta=25
°
C
A : Effective pulse breaking
line (with no margin)
B : Effective pulse critical
line (with no margin)
C : Effective pulse recommended
line (with margin)
