Application
Standards And Testing
Power Break® I I circuit breakers a re U L Listed in accordance
with Standard U L 489. This standard requires the breaker to
meet or exceed endura nce and interrupting criteria. Power
Break I I breakers are designed and tested to exceed these
requirements.
UL 489 requirements for endurance capability without cur
rent (mechanical endurance) vary with frame ratings. For
example, for a n 800-amp frame, the UL requirement is 3000
operations; and for a 4000-amp frame, only 1 100 opera
tions. All Power Break II breakers are designed to exceed this
requirement by meeting a minimum of 10,000 mechanical
operations.
Ul Test Procedu res
Extracted from U L Standard 489, current edition.
The following information briefly describes the types of tests
Power Break I I insulated case circuit breakers, rated 800
through 4000 amperes, must successfully pass.
1. Calibration:
Tested at 200%, and 135% at 25°
c.
At
200%, an 800A breaker must trip in 2 to 30 minutes de
pending on the current rating. At 135%, all sizes (larger
than 50 a m peres) must trip within 2 hours.
2. Overload:
50 operations making and breaking six times
rated current at rated minimum voltage, 0.45-0.50
power factor for 800 and 1600A frame sizes; 2000 and
2500A fram es, 25 operations at six time rated current
and, 3000 and 4000A frames, 3 operations at six time
�
rated current plus 25 operations at two times rated cur
rent. Tests a re conducted at one operation per minute,
(make and break), but may be done in groups of five
operations with 15-minute delay between groups.
Overload test is conducted in a metal enclosure rep
resenting the minimum size enclosure for which the
breaker is suitable. No electrical or mechanical break
down is permitted and a 30-ampere fuse, connected
from the metal enclosure to the line lead least likely to
a rc to the enclosure, must not rupture.
3.
Repeat 200% ca libration test.
4. Tem perature Test:
The circuit breaker after overload
is outfitted with 4 ft . minimum of rated copper cable
per pole, line and load end, and rated current is passed
through the breaker which is not in a n enclosure. After
temperatures have stabilized, the temperature rise on
the cables at the connection to the breaker wiring ter
minals must not exceed 50'C rise, (75'C total in a 25'C
room ambient), and the breaker must not trip. Cables are
sized as shown in Table 43.1. When the copper bus bars
are used instead of cable for 1600-4000A breakers, they
are sized per Table 43.2.
5. Endura nce:
The breaker must complete an endurance
test (1) making and breaking rated current at rated volt
age, .75-.80 lagging power factor and (2) additional no
38
load (mechanical) on-off operations per Table 38.1. The
g round-fault fuse described in item 2 above must not
rupture.
The rate of operation is one per minute except the 3000
and 4000A electrical test may be in groups of five with a
delay in between after conducting the first 10 operations
at one per minute.
Table 38.1
Number of Endurance Test Cycles
Frame
Number of Cycles of Operation
Size lAmps)
With Current
Without Current
800
500
3000
1600
500
2000
2000
500
2000
2500
500
2000
3000
400
1100
4000
400
1 100
6.
Repeat 200% ca libration test.
Total
3500
2500
2500
2500
1500
1500
7.
I nterrupting a bility (short-circuit)
for devices rated 600
Vac (all Power Break II breakers): Each pole of the 3-pole
un1t must complete a n "opening" ope ration
(0)
and a
"close-open" operation (CO) of short-circuit current
(single-phase) in Table 38.2 at rated voltage. An
"0"
and
"CO" operation using all three poles ("common" 3-phase
tests) is also required on the same device used for previ
ous the tests in items 1-6.
Short-circuit test a re acceptable if:
a) there is no electrical or mechanical breakdown·
b) the ground fuse has not opened;
'
c) the conductor insulation is not damaged;
d) there is continuity in the closed position at rated
voltage; and,
e) a cotton pad covering a ny vent openings i n the
enclosure has not ignited.
Short-circuit test are conducted with rated cable sizes (or bus
for 1600A and larger breakers) using a maximum of four feet
on the line side and a maximum of 10 inches on load side for
3-pole tests and four feet on load side for single-pole tests.
Table 38.2
Short-Circuit Levels
Frame Size
(Amps)
800
1600
2000
2500
3000
4000
Power
Factor, Lagging
45-.50
.25-.30
. 15-.20
. 15-.20
. 15-.20
. 15-.20
CD Circuit power factor may be .25-.30.
3-Pole Circuit Breaker -Available
Short-circuit Current Sym. Amp
1-Pole, 1-Phase
3-Pole, 3-Phase
8660
10000
14000
20000
140ooCD
25000
2ooooCD
30000
25000
35000
30000
45000
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