RFL 9300 RFL Electronics Inc.
January 30, 2002 6-68 (973) 334-3100
6.8.2 EQUATIONS FOR IEC CURVES
t
M
= curve operating time in seconds
TD = time dial setting
M = multiples of pickup. For curve operating time (t
M
), M > 1.
Curve IEC1: Standard Inverse - See Figure 6-37
t
M
= TD [ 0.14/(M
0.02
- 1) ]
Curve IEC2: Very Inverse - See Figure 6-38
t
M
= TD [ 13.5/(M - 1) ]
Curve IEC3: Extremely Inverse - See Figure 6-39
t
M
= TD [ 80.0/(M
2
- 1) ]
Curve IEC4: Long Time Backup - See Figure 6-40
t
M
= TD [ 120.0/(M - 1) ]
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