K: Thermal overload equal to (Ieq. / k* IFLA)
Where:
Ieq: Equivalent current corresponding to the largest phase current
IFLA: Full load current rating (settable)
k : Settable (1 to 1.5 step 0.01)
A: Initial thermal state. If the initial thermal state is 30% then A =0.3
Th. Trip: Trip thermal state. If the trip thermal state is set at 100%, then Th. Trip is 1
The calculation of the thermal state is given by the following formula:
Èi+1 = (Ieq /k*IFLA) ² · [1 – exp (-t/Te)] + Èi · exp (-t/Te)
TRIPPING CURVE FUNCTION OF THE PREFAULT LOAD (K = 1.1 & Te = 10 Mins)
TIME IN SEC
10000.00
1000.00
100.00
10.00
1.00
0.10
1
10
MULTIPLES OF THERMAL THRESHOLD SETTINGS Iθ>
A: No. of prefault load, thermal state = 0%
B: Thermal state = 30%
C: Thermal state = 50%
D: Thermal state = 70%
E: Thermal state = 90%
P5005ENa
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