GE Industrial Solutions ProTrip Trip Units for Low-Voltage - Manual (Page 12)

ProTrip™ Trip Units
Chapter 2. Trip Unit Setup
6
2–4 Short-Time Pickup
The short-time pickup function establishes the current at
which short-time trip is activated. Short-time pickup is
coupled with long-time pickup and the choices of pickup
settings are 1.5, 2, 2.5, 3, 4, 5, 7, and 9 times the long-time
setting. The time-current curves for short-time pickup is
illustrated in Figure 5.
Figure 5. Time-current curves illustrating short-time pickup.
2–5 Short-Time Delay
This function delays the breaker trip when the short-time
pickup function is activated. The switch settings MIN , INT ,
and MAX correspond to nominal time delays of .10, .21,
and .35 second, respectively. The delay with I 2 T IN is for a
current of 600% of C at the lower limit of the band. The
delay with I 2 T OUT is for the lower limit of each band.
The I 2 T OUT function, illustrated in Figure 6, establishes a
constant time delay. I 2 T IN biases the delay with a constant
slope, as shown in Figure 7.
2–6 Instantaneous Pickup
Instantaneous overcurrent protection causes an imme-
diate breaker trip when the chosen current setting is
reached. The pickup current may be set to 1.5, 2, 3, 5, 7,
and 9 times the rating plug current, X. Additional settings
of 10, 13, and 15 times X are also available, depending on
the breaker frame size.
Note the difference from short-time pickup, which is based
on a multiple of the long-time pickup setting, C, while
instantaneous pickup is based on the rating plug current,
X. The time-current characteristic is illustrated in Figure 8.
Figure 6. Time current curve illustrating short-time delay with I 2 T
OUT.
Figure 7. Time current curve illustrating short-time delay with I 2 T
IN.
Figure 8. Time-current curve illustrating instantaneous pickup.