Rockwell Automation 140U N-Frame Circuti Breakers Instruction Leaflet for N-Frame Circuit Breakers - Manual (Page 8)

Page 8
Fig. 3-1 Circuit Breaker Manual Controls
3.2 Circuit Breaker Reset
After an automatic or accessory initiated trip, or a manual
push-to-trip operation, the circuit breaker is reset by mov-
ing the circuit breaker handle to the extreme OFF posi-
tion.
4. N-FRAME ELECTRONIC TRIP UNIT ADJUSTMENTS
4.1 Ampere Rating
The installed rating plug establishes the maximum contin-
uous current rating (I
n
) of the circuit breaker. A typical rat-
ing plug is shown in Fig. 2-6. Available rating plugs are
listed in Table 1-2.
An optional adjustable rating plug provides four ampere
setting selections in a single rating plug. Fig. 4-1 shows
time/current curve details for adjustable rating plug.
Time/current curves for other adjustable rating plugs
are similar.
A green status light indicates the operational status of the
trip unit. If the load current through the circuit breaker
exceeds approximately 200 Amps the status light will
blink on and off once each second. A blinking status light
is an indication of a properly functioning trip unit. If the
status light is not blinking, the current through the breaker
may be less than 200 Amps. If the current exceeds 200
Amps and the status light is not blinking, use the
test kit to investigate (see section 6.8).
LACK OF ILLUMINATION OF THE STATUS LIGHT
DOES
NOT INDICATE THE TERMINALS OF THE
BREAKER ARE DEENERGIZED.
4.2 Long Time Pick Up and Delay
Neither the long time pick up or the long time delay are
adjustable. The long time pick up (the current at or above
which the circuit breaker will trip) occurs between 1.05
and 1.25 times I
n
. If the status light is on steady, it indi-
cates a trip is pending. The long delay time normally has
the characteristics t = 360 / (I
n
)
2 ±
20%. For example, at I
n
= 6 per unit, t = 10 seconds
±
20%. There is however, a
memory effect that can act to shorten the long delay. The
memory effect comes into play if a current above the long
delay pick up value exists for a time and then is cleared
by the tripping of a down stream device or the circuit
breaker itself. A subsequent overload will cause the cir-
cuit breaker to trip in shorter time than normal. The
amount of time delay reduction is inverse to the amount
of time that has elapsed since the previous overload.
Approximately five minutes is required between over-
loads to completely reset the memory.
4.3 Time and Pick-up Adjustments
One to four adjustment settings are available depending
on the particular breaker purchased. An eight -position
rotary switch is provided for each. The rotary switches
are adjusted using a small flat blade screwdriver. If the
switch is turned to a setting not marked on the trip unit
nameplate, the trip unit defaults to the minimum setting.
The available settings along with the effect of changing
each setting are illustrated in Figs. 4-2 to 4-4.
4.4 Short Delay Pick-up Setting
Seven settings are available that range from 2 to 8 times
(I
n
) as shown in Figs. 4-2 and 4-3.
4.5. Short Delay Time Setting
Four settings (I,100,200,300 milliseconds) are available
on trip units designated H (see Fig. 4-3). The I
setting gives a trip response with no intentional delay
(Instantaneous).
CAUTION
40752-093(1) Effective 5/02