14
Instantaneous Function
The instantaneous trip point establishes the value of current that
will trip the breaker without intentional time delay. Instantaneous
trip times are 50 milliseconds or less. Instantaneous trips are the
result of severe overcurrent or short-circuit conditions and dam-
age to the power system is minimized by immediate tripping.
Standard settings are adjustable in multiples of the rating plug
amp value (X). See Table 21.1 for allowable values. Maximum
setting is dependent on breaker frame size and the inclusion of a
short time function on the trip unit. Instantaneous trips are stan-
dard on WavePro breakers and can be used in conjunction with
or be replaced by the short time function. At 480 and 600 volts,
WavePro circuit breakers have the same interrupting ratings with
and without instantaneous trips. This means that the instanta-
neous trips on the breakers can be eliminated with no impact on
interrupting rating. This is beneficial when selecting the trip
characteristics of main and tie breakers, and feeders that must
coordinate with instantaneous trips downstream. There are no
“hidden” instantaneous trips on WavePro breakers when the
instantaneous function is eliminated.
Instantaneous function
Short-Time Functions (Optional)
Short-Time Pickup —
The short-time pickup function controls
the level of high current the breaker will withstand for short peri-
ods of time to allow downstream devices to clear faults without
tripping the breaker. Settings are adjustable in increments of the
breaker current setting (C). See Table 21.1 for allowable values.
If the instantaneous setting is set for lower values of current than
the short-time function, the instantaneous function prevails.
Short-time pickup function
Trip Characteristics — Power+™
Long-Time Protective Functions
Long-Time Function/Current Setting (Standard)
The adjustable long-time setting is based on multiples of “X,” the
rating plug ampere rating. There are eight possible settings from
50% to 110% of rating plug amps. This setting established the
current setting of the breaker which is the current the breaker
will carry continuously without tripping. Multiplying the long-
time setting by the rating plug value establishes the value of “C.”
For example, a breaker with a 95% long-time setting and 500
amp rating plug (X) would have a 475 amp current setting, or
value of C.
Long-time current setting (C) = (0.50 to 1.10) x rating plug (X)
Long-time function, or current setting
Long-Time Delay (Standard)
Long-time delay varies the time it will take the breaker to trip
under sustained overload conditions. It permits the breaker to
ride through momentary predictable overloads (e.g., motor start-
ing) without tripping. There are four time bands that provide
nominal delays from 3 to 25 seconds at 600% of the breaker’s
current setting, or value of C.
Long-time delay
.5
.6
.7
1.1
.8
.9
.95
1.0
1
2
3
4
1.5
2
3
5
7
9
10
13
15
1.5
2
2.5
3
4
5
7
9
