Rockwell Automation 140U N-Frame Circuti Breakers Instruction Leaflet for N-Frame Circuit Breakers - Manual (Page 2)

Page 2
ature operating range. Consult Allen-Bradley for recom-
mendations.
Molded Case Switches: The Molded Case Switch is
similar to the Circuit Breaker except that it does not have
a replaceable rating plug and has a different tripping
characteristic. There is a fixed instantaneous trip at
15,000 Ampere but there is no overload short delay or
ground fault trip. As a result sections 2.6, 2.7, 4, 5, 6.8
and 7 are not applicable. In the remaining sections the
term circuit breaker shall also include the molded case
switch.
100 Percent Rated N-Frame Circuit Breaker:
Circuit breakers are suitable for continuous
operation at 100 percent of the frame rating in an
enclosure which measures at least 42” height, 22 3/4”
width and 11 1/2” depth. The 800A version requires no
ventilation. The 1200A version requires 224 inch
2
ventila-
tion on the front face of the enclosure (72 sq. in. top, 72
sq. in. bottom, 40 sq. in. left and 40 sq. in. right). Further-
more the 1200A version has to be used with the supplied
conductor extensions and terminal barriers as shown in
Figure 2-2. Use only 90°C rated wire with ampacity
based on 75°C rated conductors. Use Copper only or
AL9CU terminals only.
Overcurrent Trip: In accordance with standards require-
ments, the trip unit initiates a trip of the circuit breaker
within two hours for an overcurrent of 135 percent, and a
trip in less time for higher overloads.
A “Thermal Memory” effect prevents the breaker from
being re-energized immediately after an overcurrent. A
“cooling off” period of up to 5 minutes is required, which
allows time for cabling to cool off.
Short delay/Instantaneous Trip: For short circuit condi-
tions that exceed the short delay pick-up settings, the trip
units initiates a trip after a delay prescribed by the I
2
t
ramp function for trip units designated L and G. A flat
response time delay action is provided by trip units desig-
nated H unless the instantaneous (I) setting is selected.
➀ Fixed rating plugs available, see table 1-2.
➁ Optional four-setting adjustable rating plugs available, see table 1-2.
➂ Using trip unit with adjustable delay (H), instantaneous pick-up is achieved when the lowest time delay set-
ting (I) is selected.
➃ Override setting fixed at frame withstand rating.
TABLE 1-1: ELECTRONIC RMS TRIP UNIT TYPES
Trip Unit Functions Electronic
L H G S
Long Time Fixed Ampere Rating ➀ with Fixed
Long Delay
Adjustable Ampere Setting with Fixed
Long Delay
➁
●
●
●
●
●
●
Short Time Adjustable Short Time Pick-up with
Short Time Delay I
2
t Ramp
Adjustable Short Time Delay ➂ with
Adjustable Short Time Pick-up, or
Adjustable Instantaneous Pick-up ➂
●
●
●
●
Instantaneous Fixed Instantaneous (Override) ➃ ● ● ●
Ground Fault Adjustable Ground Fault Pick-up with
Adjustable Ground Fault Time ●
40752-093(1) Effective 5/02