Explanations: Aircraft Electrical Systems Flashcards
Why is a ring type electrical terminal used on most aircrafts?
If the nut on the terminal stud becomes loose, the ring-type terminal will remain on the stud whereas a hook or slotted terminal will slip off.
What happens when the load of a generator equipped with a vibrator-type voltage regulator is great?
The voltage drops and the voltage regulator points must remain closed longer to allow the voltage to rise.
When the load is light, the voltage is high and the points remain closed a very short time.
What is generator brush arcing?
an excess spark, which can be caused by the brushes not having proper contact with the commutator.
Why does a series wound motor have high starting torque?
the same current that passes through the armature also passes through the field windings.
What happens if the frequency of two ac generators connected in parallel are not equal?
A mismatch in frequencies of the two AC generators will cause the generator with the lower frequency to be picked up as a load on the other generator (a condition referred to as “motoring”). This can cause an overload in the generators and the distribution system.
What does a armature brake do?
It causes the armature to stop turning as soon as the switch is released.
What will happen if armature reaction is not corrected?
It will cause the brushes to arc under certain load conditions.
What is armature reaction?
Armature reaction weakens the main flux. In the case of a dc generator, the weakening of the main flux reduces the generated voltage
What are interpoles?
Interpoles are small electromagnets placed between the main poles of a generator. They are used to improve the performance of the generator by reducing voltage fluctuations and increasing the efficiency of the machine.
What are pole pieces (or poles shoes)?
A structure composed of material of high magnetic permeability that serves to direct the magnetic field produced by a magnet. A pole piece attaches to and in a sense extends a pole of the magnet, hence the name. Pole pieces are used with both permanent magnets and electromagnets.
What are field coils?
A coil that generates a magnetic field when an electric current is passed through it.
What are current cutout relays?
Sometimes called the circuit breaker, this device is a magnetic “make-and-break “ switch. It connects the generator to the battery circuit when the generator’s voltage builds up to the desired value. It disconnects the generator when it slows down or stops.
How does the magnetic brake used to stop rotation of an electric motor armature operate?
a magnetic brake used to stop rotation of an electric-motor armature is applied by spring force and is released by an electromagnet energized when the motor is turned on.
As soon as the motor is turned off, the spring applies the brake and stops the rotation of the armature.
What is a brush pigtail?
A pigtail connects a brush to the power supply. A pigtail is an extended, flexible connection or a braided copper conductor. Brush material must have good conductivity and be soft enough not to damage the copper segments of the commutator.
How does the brush pigtail eliminate sparking?
All of the current is carried from the brush into the holder through the pigtail rather than through the sliding contact made between the brush and the brush guide.
Why does a series-wound DC electric motor require less current at high RPMs?
The current drops off as the armature speed and the counter EMF builds up.
What are the purposes of interpoles?
They are used in high-output compound-wound DC generators to counteract field distortion and to overcome armature reaction. Armature reaction causes arcing at the brushes.
They don’t reduce field strength, they increase it.
When a DC generator is overhauled, what is done with the commutator?
It is turned on a lathe until it is perfectly round and smooth.
After the commutator it turned, the mica separators between the commutator bars are undercut to approximately the width of the mica, or somewhere in the neighborhood of 0.02 inch.
Where is the integral fan of a generator mounted?
on the armature shaft.
