Aerospace circuit
breakers.
Inspection of aircraft
circuit-protection devices.
In aircraft, all electrical wires must be provided with some means of circuit
protection. Electrical wire should be protected with circuit breakers or fuses located as close as possible
to the electrical power source bus. Normally, the manufacturer of electrical equipment will specify the fuse
or breaker to be used when installing the respective equipment.
Resettable circuit
protection devices.
a. All resettable type circuit breakers must open the circuit irrespective of the
position of the operating control when an overload or circuit fault exists. Such circuit breakers are
referred to as "trip free."
b. Automatic reset circuit breakers, that automatically reset themselves periodically,
are not recommended as circuit protection devices for aircraft.
In aircraft circuit breakers are designed as circuit protection for the wire, not for
protection of black boxes.
Determination of
circuit breaker ratings.
Aircraft Circuit protection devices must be sized to supply open circuit capability.
Aerospace circuit breakers must be rated so that they will open before the current rating of the wire
attached to them is exceeded, or before the cumulative rating of all loads connected to them are exceeded,
whichever is lowest.
A circuit breaker must always open before any component downstream can overheat and
generate smoke or fire. Wires must be sized to carry continuous current in excess of the circuit protective
device rating, including its timecurrent characteristics, and to avoid excessive voltage
drop. Use of a circuit breaker as a switch is not recommended. Use of a circuit breaker as
a switch will decrease the life of the circuit breaker.
Circuit breaker
maintenance.
Aerospace Circuit breakers should be periodically cycled with no load to enhance
contact performance by cleaning contaminants from the contact surfaces.
|