GEK-106310AB F650 Digital Bay Controller 5-41
5 SETTINGS 5.4 PROTECTION ELEMENTS
5
5.4.2.4 ANSI CURVES
This family of curves complies with the American Standard ANSI C37.90 for Extremely inverse, Very inverse, Normally
inverse and Moderately inverse curves. The formulas that define these curves are as follows:
where:
T = Operation time (in seconds).
Dial = Multiplying factor
I = Input current
I
pickup
= Current pickup setting
A, B, C, D, E = Constants
T
reset
= Reset time (in seconds) assuming a 100% of power capacity and that the reset is activated
T
r
= Characteristic constant
The different constants that define the above-mentioned curves are:
Table 5–36: CONSTANTS FOR ANSI CURVES
ANSI CURVE SHAPE A B C D E TR
ANSI Extremely Inverse 0.0399 0.2294 0.5 3.0094 0.7222 5.67
ANSI Very Inverse 0.0615 0.7989 0.34 -0.284 4.0505 3.88
ANSI Normally Inverse 0.0274 2.2614 0.3 -4.1899 9.1272 5.95
ANSI Moderately Inverse 0.1735 0.6791 0.8 -0.08 0.1271 1.08
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