MIL-DTL-17361G(SH)
4.5.9.2.2 Undervoltage release device. Undervoltage release device shall trip the circuit breaker for the number
of operations specified in Tables III (a) and III (b).
4.5.9.2.3 Shunt trip. Shunt trip shall trip the circuit breaker for the number of operations specified in Table IV.
4.5.9.2.4 Example. An electrical endurance test procedure for an AQB-A250 circuit breaker with a shunt trip,
an undervoltage release device, and an electric operating mechanism would be conducted as follows:
a. Subject the circuit breaker to 1500 trip operations by closing the circuit breaker with the electric motor
operator, tripping the circuit breaker by energizing the shunt trip, and resetting the circuit breaker to "OFF" by
utilizing the electric motor operator.
b. Subject the circuit breaker to 2500 trip operations by closing the circuit breaker with the electric motor
operator, tripping the circuit breaker by de-energizing the undervoltage releases, and resetting the circuit breaker to
"OFF" by utilizing the electric motor operator.
4.5.10 Calibration.
4.5.10.1 Circuit breakers with thermal magnetic trip units.
4.5.10.1.1 Long-time delay. Circuit breakers shall be tested in accordance with Table XI. LTD elements shall
be tested with current flowing through all three poles in series. The tests shall start with the circuit breaker parts at
ambient room temperature. LTD tests shall be conducted at 50±5 °C ambient temperature. Sufficient time between
tests shall be allowed for adequate cooling of the circuit breaker.
TABLE XI. Long-time delay testing (thermal magnetic trip units).
Current level applied /1
Actual trip time
Required trip time /2
NOTE:
/1 Current levels as specified in the applicable specification sheets (see 3.1).
/2 Required trip time as specified in the applicable specification sheets (see 3.1).
4.5.10.1.2 Instantaneous trip elements. Tests shall be made on each pole of the circuit breaker at the current
and frequencies required for instantaneous tripping to ensure that the calibration is within the limits and tolerances
specified in the individual specification sheets (see 3.1). Instantaneous tests shall be conducted at 50±5 °C ambient
temperature. The tests shall be performed on each pole a minimum of three times at the instantaneous settings
identified in Tables XII and XIII. Sufficient time between tests shall be allowed for adequate cooling of the circuit
breaker. The current asymmetry shall not exceed 5 percent on the first two half cycles. The pulse duration shall be
between 5 cycles and 10 cycles. The tests shall be in accordance with the pulse method as per NEMA test schedule
AB-4 (see 6.4.19).
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