MIL-PRF-24021K
3.4.4.1.2 Phase sequence. The correct phase sequence at the electric receptacle of the monitor
is 1-2-3 or A-C-E, as applicable, and the monitor shall not reset if the sequence is otherwise.
3.4.4.1.3 AC reset response time. The AC power monitor reset response time shall be
measured from the time the reset switch is closed until the monitor connects power to the external
power contactor coil. Reset response time shall be as specified in table II.
3.4.4.1.4 AC trip response time. The AC power monitor trip response time shall be measured
from the time the applied voltage or frequency goes outside the steady-state voltage or frequency
limits in table II until the monitor disconnects power from the external power contactor coil.
3.4.4.2 Operation of DC monitors.
3.4.4.2.1 Normal operation of DC monitors. The DC power monitor shall connect external
power to the aircraft load via operation of the external power contactor (reset) only when the
external power is of the proper polarity, the voltage and ripple are within the reset limits in
table III and on figure 9, the voltage at pins C and E is less than 1.5 volts, and the reset switch is
momentarily closed. The monitor shall not require the release of the reset switch to activate its
switching circuit between pins G and A. The DC monitor upon reset shall not engage the load, or if
in operation shall disconnect the load (trip) when the voltage or ripple or both are outside the limits
in table III and on figure 9. The potential applied to pin G of the monitor shall be applied to the coil
of the external power contactor by the switching circuit in the monitor. However, operation shall
be controlled by the potential applied to pin B of the monitor.
3.4.4.2.2 Inhibited operation of DC monitors. The monitor shall perform in an inhibited mode
as specified in 3.4.2.2.
3.4.4.2.3 DC reset response time. The reset response time shall be measured from the time the
reset switch is closed until the monitor connects power to the external power contactor coil. Reset
response time is specified in table III.
3.4.4.2.4 DC trip response time. The DC monitor trip response time shall be measured from
the time the applied power goes outside the steady-state limits in table III until the monitor
disconnects power from the external power contactor coil. Trip response times are specified in
table III.
3.4.4.2.5 Polarity. The DC monitor shall sense the polarity of the applied voltage. The
monitor shall not connect external power to the load (reset) when the polarity is incorrect.
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