P4083ENb
Time t
100 ms
1 x I>
1.13 x I>
Current I
40 ms
Figure 31: Definite time overcurrent element
Setting guidelines
T
o prevent operation during starting the instantaneous element is usually set to 1.25 times the maximum starting
current.
The timer setting is system dependent and can be set to a value in the region of 100 ms. A time delay setting of
less than 2 cycles duration is not realistic due to the fact that a minimum confirmation time, equivalent to two
cycle duration, is required before tripping.
Note:
If the motor is controlled by a fused contactor it needs to be coordinated with the fuse. This prevents the contactor attempting
to interrupt current in excess of its breaking capacity.
Setting example
Utilizing the pr
eviously specified motor parameters, set:
I>Current Set = (1.25 x 4.7 x 293)/300 = 5.7 In
I> Time Delay = 100 ms
Chapter 6 - Current Protection Functions P24xM
100 P24xM-TM-EN-2.1
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