MIL-PRF-55629E
4.8.5 Calibration (see 3.9).
4.8.5.1 Method I (used for qualification inspection). Circuit breakers shall be mounted by their normal mounting
means (see 3.5.5) and tested in the vertical mounting position. Circuit breakers shall be connected as shown on
figure 1, with leads and terminals attached as specified. Tripping times shall then be measured when circuit breakers
are subjected to the specified percentages (see 3.1) of rated current applied as a step function (ac or dc), except for
100 percent. The sample units shall be divided as evenly as possible (with respect to current rating and time delay)
into three groups for testing at the following voltages and frequencies: 50 V dc, 240 V ac at 60 Hz, and 240 V ac at
400 Hz. There shall be sufficient time (not less than 10 minutes) between each application of current to permit proper
cooling of the circuit breaker. Circuit breakers rated for high inrush (see 3.1) shall be subjected to a half wave of a 60
Hz waveform for 60 Hz devices and a half wave of a 400 Hz or 60 Hz waveform for dc and 400 Hz devices. The
peak value of the half wave shall be as specified, (see 3.1). Normally, tests shall be conducted within the rated
operating voltage (see 3.5.12). However, if the inherent resistance or impedance of the circuit breaker precludes
attainment of the required percentages of overload current at the rated operating voltage, for the purpose of
determining tripping times and high inrush capabilities, the voltage shall be increased as necessary, up to a maximum
of 40 percent. If the specified overload current cannot be obtained with a maximum increase in voltage of 40 percent,
tests of these particular overload levels shall be omitted with qualification activity approval. Each section of multipole
breakers shall be subjected to the calibration current specified, with remaining pole or poles passing no current.
4.8.5.2 Method II (used for group A inspection, high-temperature and low-temperature operation, endurance,
moisture resistance, trip-free calibration, and interrupting capacity). Circuit breakers shall be tested as specified in
4.8.5.1, except that only 125 percent and/or 150 percent (as specified), and 200 percent of rated current shall be
applied, and the applied voltage should be at a level sufficient to maintain the specified percent of rated current
during testing.
4.8.6 Resistance or impedance (see 3.10). With the circuit breakers mounted in their normal vertical mounting
position, the resistance or impedance shall be measured between main terminals of each pole at 100 percent rated
current, and applicable frequency (see 3.1), using the voltmeter-ammeter method. These measurements shall be
made and recorded after the circuit breaker has been subjected to these conditions for 1 hour. Auxiliary contact
resistance shall be measured using the voltmeter-ammeter method with a 20 V ac or V dc source with limiting
resistance to 1 ampere. Both the normally open and normally closed contacts shall be measured. The voltage
sensitive poles shall be measured using the volt-ammeter method using a 20 volts minimum ac or dc source with
limiting resistance to 100 milliamperes. All measurements herein shall comply with the requirements of 3.10.
4.8.7 Actuator (see 3.11).
4.8.7.1 Actuator strength (lever type) (see 3.11.1). Circuit breakers shall have the specified load (see 3.1) applied
to the tip of the actuator lever for 1 minute under each of the following conditions:
a.
Normal to the lever axis in the plane of lever travel at each extreme position of the lever.
b.
Normal to the lever axis and normal to the plane of lever travel at each extreme position of the lever.
c.
Coaxial with the lever axis toward the lever pivot throughout the entire range of lever travel.
d.
Coaxial with the lever axis away from the lever pivot throughout the entire range of lever travel.
Circuit breakers shall be examined for evidence of mechanical damage.
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