Application
II. Rated Service Short-Circuit Breaking Capacity (lcs)
1. Rated Service Short-Circuit Brea king Capacity:
Power Break® I I circuit breakers are tested to com plete
a series of short-circuit interruptions with a 3-minute
rest period between interruptions. The breakers m ust
complete an "open" operations followed by a "close
open" operation and another "close-open" operation.
The circuit breakers are tested with an open circuit
voltage sufficient to enable a recovery voltage of the
rated voltage plus 5%. The 800-2000 amp Power Break I I
circuit breakers a re tested in a 5 6,000 amps rms sym
metrical, 50 Hz, 20% power factor short circuit. (See
Table 46. 11
2. Verification of Dielectric Withstand:
Following the short-circuit interruptions, the breaker's
main circuit is verified to withstand a voltage equal to
twice its rated insulation voltage for 1 minute.
3.
Verification of Tem perature Rise:
Following the dielectric verification, a temperature-rise
test is made at the rated current and the main terminals
a re monitored as previously described in Sequence I test
5.
4. Verification of Overload Release:
Following the temperature-rise verification, the circuit
breaker overload protection is verified by a pplyin g 145%
of rated current through all three poles connected in
series. The breaker must trip within trip time curve.
I l l . Rated U ltimate Short-Circuit Breaking Capacity
(leu)
1. Verification of Overload Release:
Prior to short-circuit testing, the circuit breaker overload
protection is verified by applying 200% of rated current
through each pole individually. The breaker must trip
within the trip time curve.
2. Rated U ltimate Short-Circuit Breaking Capacity:
Power Break I I circuit breakers a re tested to com plete a
series of short-circuit interruptions with a 3 minute rest
period between interruptions. The breakers m ust com
plete an "open" operation followed by a "close-open"
operation. The circuit breakers are tested with an open
circuit voltage sufficient to enable a recovery voltage of
the rated voltage plus 5%. The 800 - 2000 amp Power
Break II circuit breakers are tested in a 75,000 a m p rms
symmetrical 50 Hz, 20% power factor short circuit.
3.
Verification of Dielectric Withsta nd:
Following the short-circuit interruptions, the breaker's
main circuit is verified to withstand a voltage equal to
twice its rated insulation voltage; however, not less than
1000V for 1 minute.
4. Verification of Overload Release:
Following the dielectric verification, the circuit breaker
overload protection is verified by applying 250% of rated
current through each pole individually. The breake r m ust
trip within the trip time curve.
IV. Rated Short-Time Withstand Current (lew)
1. Verification of Overload Release:
Prior to short-circuit testing, the circuit breaker overload
protection is verified by a pplying 200% of rated current
through each pole individually. The breaker must trip
within the trip time curve.
2. Rated Short-Time Withstand Cu rrent:
Power Break I I Circuit breakers are tested to carry a
short-time withstand current with the overcurrent and
instantaneous over-ride protection defeated. For the
800-2000 amp Power Break II circuit breakers, a short
circuit is calibrated to deliver the equivalent I2T of a
40,000 amp rms symmetrical short circuit for 1 second
or 1,600,000,000 I2T. Also, the test circuit is calibrated to
reach a peak current of at least 84,000 amps during its
first half cycle. Since momentary contact separation can
occur during this test, the test is made at rated voltage.
The test is performed at a frequency of 50 Hz with a plus
or minus 25% tolerance and a 25% power factor.
3.
Verification of Temperature Rise:
Following the short-time withstand, a temperature-rise
test is made at the rated current and the main terminals
a re monitored as previously described in Sequence I test
5 .
4. Short-Circuit Breaking Capacity at the Maximum
Short-Time Withstand Current:
Following the temperature verification the breakers are
tested to complete a series of short-circuit interruptions
with a 3-minute rest period between interruptions. The
breakers must complete an "open" operation followed by
a "close-open" operation. The circuit breakers are tested
with an open circuit voltage sufficient to enable a recov
ery voltage of the rated voltage plus 5%. The 800-2000
amp Power Break II circuit breaker is tested in a 40,000
amp rms symmetrical, 50 Hz, 25 % short circuit.
5. Verification of Dielectric Withstand:
Following the short-ci rcuit interruptions, the breaker's
main circuit is verified to withstand a voltage equal to
twice its rated insulation voltage for 1 minute.
6.
Verification of Overload Release:
Following the dielectric verification, the circuit breaker
overload protection is verified by applying 250% of rated
current through each pole individually. The breaker must
trip within the trip time curve.
41
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