System information
™
Masterpact™ NT and NW Universal Power Circuit Breakers
Micrologic™ Electronic Trip Systems
33
05/2014
© 2000–2014 Schneider Electric
All Rights Reserved
Micrologic Trip Unit Functions
Long-Time Trip Functions
The long-time pickup switch sets the maximum current level the circuit
breaker will carry continuously. The maximum current level (I
r
) is the long-
time pickup setting multiplied by the sensor plug amperage (I
n
). If the current
exceeds this value for longer than the long-time delay time, the circuit
breaker will trip.
The long-time delay switch sets the length of time that the circuit breaker will
carry a sustained overload before tripping. Delay bands are labeled in
seconds of overcurrent at six times the ampere rating. For maximum
coordination, there are eight delay bands. Long-time delay is an “inverse
time” characteristic in that the delay time decreases as the current
increases.
The trip unit includes an alarm indicator that will be lit continuously when the
current is above 100% of the pickup setting.
Short-Time Trip Functions
The short-time pickup switch sets the short-circuit current level at which
the circuit breaker will trip after the set short-time delay. The short-time
current (I
sd
) equals the short-time pickup setting multiplied by the long-
time pickup (I
r
).
The short-time delay switch sets the length of time the circuit breaker will
carry a short circuit within the short-time pickup range. The delay (based
on 10 times the ampere rating I
r
) can be adjusted to four positions of I
2
t
ramp operation (I
2
t ON) or five positions of fixed time delays (I
2
t OFF). I
2
t
ON delay is an “inverse time” characteristic in that the delay time
decreases as the current increases. Short-time delay for the 2.0 trip unit is
fixed at a delay band of 20 to 80 ms.
Instantaneous Trip Function
The instantaneous pickup switch sets the short-circuit current level at which the circuit breaker will trip
with no intentional time delay. The instantaneous current (I
i
) is equal to the instantaneous pickup
setting multiplied by the sensor plug amperage (I
n
).
The instantaneous function will override the short-time function if the instantaneous pickup is adjusted
at the same or lower setting than the short-time pickup. In trip units with both adjustable short-time and
instantaneous trip functions, the adjustable instantaneous trip can be disabled by setting
Instantaneous pickup to OFF.
Ground-Fault Trip Functions
The ground-fault pickup switch sets the current level at which the circuit
breaker will trip after the set ground-fault delay. Ground-fault pickup values
(I
g
) are based on circuit breaker sensor plug (I
n
) only, not on the rating plug
multiplier (I
r
). Changing the rating plug multiplier has no effect on ground-fault
pickup values.
The ground-fault delay switch sets the length of time the circuit breaker will
carry ground-fault current which exceeds the ground-fault pickup level before
tripping. The delay (based on the sensor plug amperage (I
n
) can be adjusted
to four positions of I
2
t ramp operation (I
2
t ON) or five positions of fixed time
delays (I
2
t OFF). I
2
t ON delay is an “inverse time” characteristic in that the
delay time decreases as the current increases.
.4
.5
.6
.7
.8
.9
.95
.98
1
delay
short time
I itsd
(s)
on I2t
.2
.3
.4
.4
.1
.2
.3
.1
0
off
instantaneous
long time
alarm
Ir
x In
ground fault
B
C
D
E
F
G
H
J
Ig
tg
(s)
on I2t
.2
.3
.4
.4
.1
.2
.3
.1
0
off
A
setting
x Ir
2
2.5
3
4
5
6
8
10
Isd
1.5
.5
1
2
4
8
12
16
20
tr
(s)
@ 6 Ir
24
x In
3
4
6
8
10
12
15
off
2
test
Long-Time
Pickup
Long-Time
Delay
Alarm
Indicator
Long-Time Trip Functions
Short-Time and
Instantaneous Trip
Functions
Ground-
Fault
Pickup
Ground-
Fault
Delay
.4
.5
.6
.7
.8
.9
.95
.98
1
delay
short time
I itsd
(s)
on I2t
.2
.3
.4
.4
.1
.2
.3
.1
0
off
instantaneous
long time
alarm
Ir
x In
ground fault
B
C
D
E
F
G
H
J
Ig
tg
(s)
on I
2
t
.2
.3
.4
.4
.1
.2
.3
.1
0
off
A
setting
x Ir
2
2.5
3
4
5
6
8
10
Isd
1.5
.5
1
2
4
8
12
16
20
tr
(s)
@ 6 Ir
24
x In
3
4
6
8
10
12
15
off
2
test
Ground-Fault Trip
Functions