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Pick-up characteristic
The IDMT characteristic is applied when the operation of the UVS1 element is required
inversely in accordance with the level of input voltage. The IDMT characteristic curve is
illustrated in Figure 2.25-2 using a value of time multiplier is set for [UV1-TMS]. It is followed
to Equation (2.25-1) in conformed in IEC 60255-127
where,
t = operating time (seconds),
V = energizing voltage (voltage),
Vs = pickup voltage setting (voltage),
TMS = time multiplier setting.
Figure 2.25-2 IDMT characteristics curves depending on TMS
Drop-off characteristic
The user should set the time for resetting in the IDMT characteristic. Figure 2.25-3 shows
examples of the pick-up and the drop-off relevant to both the fault occurrences and the
1.000
10.000
100.000
1000.000
0 0.2 0.4 0.6 0.8 1
Operating Time (secs)
Applied Voltage (x Vs)
Undervoltage Inverse Time Curves
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