MIL-DTL-17587C(SH)
4.5.12 Short-time duty cycle performance (withstand rating). Circuit breakers shall be subjected to their rated
short-time current at rated voltage for a time duration as shown in the applicable specification sheet. No repairs or
replacement of parts shall be required after the test.
4.5.12.1 Short-time current characteristics. The short-time current is expressed in root mean square (rms)
symmetrical A and is measured from the envelope of the available current wave at 0.5 cycles after current is
established. For three-phase circuits, the symmetrical current value shall be the average of the phase currents. The
test circuit shall demonstrate that circuit breakers perform their short-circuit duty cycle with all degrees of current
asymmetry produced by three-phase circuits, having a short-circuit power factor of 0.15 lagging or less (X/R ratio of
6.6 or greater).
4.5.12.2 Test circuit.
4.5.12.2.1 AC test circuit. AC test circuit and test procedures shall be in accordance with the requirements of
ANSI C37.50 as modified by the requirements of this specification.
4.5.12.2.2 DC test circuit. DC circuit breakers may be tested for the required short-time current on an AC
circuit in which the peak currents do not exceed the specified level of short-time current.
4.5.13 Interrupting current duty cycle performance. Circuit breakers shall be subjected to their rated short-
circuit interruption current at rated voltage in accordance with the applicable specification sheet. When specified in
the qualification package, the emission indicator (cheesecloth) shall not ignite during testing. Scorching of the
cheesecloth shall not be considered as ignition. No repairs or replacement of parts shall be required after the test.
4.5.13.1 Interrupting duty cycle. The interruption duty cycle of circuit breakers with instantaneous overcurrent
trip elements shall consist of an opening operation, followed by a 2-minute interval, then by a close-open operation,
and after a 5-minute interval, by another close-open operation.
4.5.13.2 Interrupting current characteristics. The short-circuit current is expressed in rms symmetrical amperes
and is measured from the envelope of the available current wave at 0.5 cycle after current is established. For three-
phase circuits, the symmetrical current value shall be the average of the phase currents. The test circuit shall
demonstrate that circuit breakers perform their short-circuit duty cycle with all degrees of current asymmetry
produced by three-phase circuits, having a short-circuit power factor of 0.15 lagging or less (X/R ratio of 6.6 or
greater). The rms symmetrical current shall be calculated in accordance with ANSI/IEEE C37.09.
4.5.13.3 Test circuit/setup.
4.5.13.3.1 AC test circuit. AC test circuit and test procedures shall be in accordance with the requirements of
ANSI C37.50, as modified by the requirements of this specification.
4.5.13.3.2 DC test circuit. In DC test circuits, the test shall be performed on the two poles connected in series.
The test circuit shall be so adjusted that the requirements in Table XVIII are met.
TABLE XVIII. Requirements for DC interrupting test.
Short circuit
Time constant
Maximum initial current rise
current
L/R
E/L (at 240 V)
(amperes)
(milliseconds)
(amperes per microsecond)
50,000
16.0
3.1
75,000
15.6
4.8
150,000
12.5
12.0
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