GE Industrial Solutions WavePro Low-Voltage Power Circuit Breakers - Manual (Page 23)

MicroVersaTrip Plus™ and MicroVersaTrip PM™ Trip Units
Chapter 2. Setup Mode
15
Figure 12. Time-current curve illustrating short-time pickup.
Short-Time Delay
The Trip Unit display for short-time delay is shown in
Figure 13. This function delays the breaker trip on a short-
time trip. The choices of time-delay bands are listed in
Table 11. The delay with
I
2
T IN is for a current of 600% of
xLT at the lower limit of the band. The delay with I
2
T OUT
is for the lower limit of each band.
On ANSI Trip Units ordered with the user-selectable,
switchable instantaneous overcurrent and ground-fault
option, “X,” an additional value of
OFF appears at the end
of the delay band settings. Choosing OFF disables short-
time protection. The short-time OFF band is interlocked
with instantaneous pickup, so that only one function can
be turned off at a time.
The I
2
T OUT function, illustrated in Figure 14, establishes
a constant time delay. I
2
T IN biases the delay with a con-
stant slope, as shown in Figure 15.
Figure 13. Trip Unit display for short-time delay.
Band Time Delays, sec
1 0.10
2 0.21
3 0.35
Table 11. Lower-limit delays for I
2
T OUT short-time delay bands.
Figure 14. Time-current curve for short-time delay with I
2
T OUT .
Figure 15. Time-current curve for short-time delay with I
2
T IN .
Instantaneous Pickup
Instantaneous overcurrent protection, with Trip Unit dis-
play illustrated in Figure 16, causes an immediate breaker
trip when the chosen current level is reached. The pickup
value may be set in steps of 0.5 xIn from 1.5 xIn to a maxi-
mum dependent on the frame size and the presence of the
short-time function, as listed in Table 12.
Note the difference from short-time pickup, which is based
on a multiple of xLT. The time-current characteristic is
shown in Figure 17.
Figure 16. Trip Unit display for instantaneous pickup.