The operate times for the ANSI and IEC IDMT curves are defined with the
coefficients A, B and C.
The values of the coefficients can be calculated according to the formula:
t s
A
I
I
B k
c
[ ] =
>
−
+
⋅
1
A060821 V2 EN (Equation 77)
t[s] Operate time in seconds
I measured current
I> set
Start value
k set
Time multiplier
Table 707: Curve parameters for ANSI and IEC IDMT curves
Curve name
A B C
(1) ANSI Extremely
Inverse
28.2 0.1217 2.0
(2) ANSI Very Inverse 19.61 0.491 2.0
(3) ANSI Normal
Inverse
0.0086 0.0185 0.02
(4) ANSI Moderately
Inverse
0.0515 0.1140 0.02
(6) Long Time
Extremely Inverse
64.07 0.250 2.0
(7) Long Time Very
Inverse
28.55 0.712 2.0
(8) Long Time Inverse 0.086 0.185 0.02
(9) IEC Normal Inverse 0.14 0.0 0.02
(10) IEC Very Inverse 13.5 0.0 1.0
(11) IEC Inverse 0.14 0.0 0.02
(12) IEC Extremely
Inverse
80.0 0.0 2.0
(13) IEC Short Time
Inverse
0.05 0.0 0.04
(14) IEC Long Time
Inverse
120 0.0 1.0
1MRS758755 A Section 11
General function block features
REC615 and RER615 717
Technical Manual
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