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PROTECTION
MULTIPLIER
CURRENT (I/I
(TDM)
1.5
0.5
3.220
1.0
6.439
2.0
12.878
4.0
25.756
6.0
38.634
8.0
51.512
10.0
64.390
Table 4-23: ANSI CURVE TRIP TIMES (IN SECONDS)
MULTIPLIER
CURRENT (I/Ipickup)
(TDM)
1.5
ANSI EXTREMELY INVERSE
0.5
2.000
1.0
4.001
2.0
8.002
4.0
16.004
6.0
24.005
8.0
32.007
10.0
40.009
ANSI VERY INVERSE
0.5
1.567
1.0
3.134
2.0
6.268
4–174
)
pickup
2.0
3.0
4.0
1.902
1.216
0.973
3.803
2.432
1.946
7.606
4.864
3.892
15.213
9.729
7.783
22.819
14.593
11.675
30.426
19.458
15.567
38.032
24.322
19.458
ANSI CURVES
The ANSI time overcurrent curve shapes conform to industry standards and the ANSI
C37.90 curve classifications for extremely, very, and moderately inverse. The ANSI curves
are derived from the following formulae:
Where:
T = operate time (in seconds)
TDM = Multiplier setting
I = input current
I
= Pickup Current setting
pickup
A to E = constants
T
= reset time in seconds (assuming energy capacity is 100% and RESET is
RESET
"Timed")
t
= characteristic constant
r
Table 4-22: ANSI INVERSE TIME CURVE CONSTANTS
ANSI CURVE SHAPE
ANSI Extremely Inverse
ANSI Very Inverse
ANSI Normally Inverse
ANSI Moderately Inverse
2.0
3.0
4.0
0.872
0.330
0.184
1.744
0.659
0.368
3.489
1.319
0.736
6.977
2.638
1.472
10.466
3.956
2.208
13.955
5.275
2.944
17.443
6.594
3.680
0.663
0.268
0.171
1.325
0.537
0.341
2.650
1.074
0.682
5.0
6.0
7.0
0.844
0.763
0.706
1.688
1.526
1.412
3.377
3.051
2.823
6.753
6.102
5.647
10.130
9.153
8.470
13.507
12.204
11.294
16.883
15.255
14.117
A
B
C
0.0399
0.2294
0.5000
0.0615
0.7989
0.3400
0.0274
2.2614
0.3000
0.1735
0.6791
0.8000
5.0
6.0
7.0
0.124
0.093
0.075
0.247
0.185
0.149
0.495
0.371
0.298
0.990
0.742
0.596
1.484
1.113
0.894
1.979
1.483
1.192
2.474
1.854
1.491
0.130
0.108
0.094
0.260
0.216
0.189
0.520
0.432
0.378
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
8.0
9.0
10.0
0.663
0.630
0.603
1.327
1.260
1.207
2.653
2.521
2.414
5.307
5.041
4.827
7.960
7.562
7.241
10.614
10.083
9.654
13.267
12.604
12.068
D
E
t
r
3.0094
0.7222
5.67
-0.2840
4.0505
3.88
-4.1899
9.1272
5.95
-0.0800
0.1271
1.08
8.0
9.0
10.0
0.063
0.055
0.049
0.126
0.110
0.098
0.251
0.219
0.196
0.503
0.439
0.393
0.754
0.658
0.589
1.006
0.878
0.786
1.257
1.097
0.982
0.085
0.078
0.073
0.170
0.156
0.146
0.340
0.312
0.291
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