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xxxAEIS > DC Systems > Flashcards

DC Systems Flashcards

1
Q

what are generators

A

electromagnetic devices that converts mechanical energy into electrical energy by electromagnetic induction

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2
Q

what maintains the aircraft battery at its fully charged condition?

A

dc generator

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3
Q

purpose of reverse current cut out relay

A

prevent battery current from flowing into generators (may burn armature)

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4
Q

sequence of start up power

A

engine starts generator > voltage regulator > RCR

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5
Q

2 components in a dc generator, and which is stationary

A

stator (stationary)

rotor (turns)

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6
Q

components in a stator and its purpose

A

magnetic frame (yoke) - provides path for the flux produced

poles - provides low reluctance path for the magnetic flux

field coils - produces magnetic flux

brushes & bearings - collects current from the commutator and delivers to external load circuit

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7
Q

components in a rotor and its purpose

A

armature core - provides low reluctance path for the magnetic flux

armature windings - to generate emf if the machine is generator/ to allow current to flow and develop force if machine is motor

commutator - rectify ac current into dc current

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8
Q

4 types of dc generator

A

series, shunt, compound, separately-excited

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9
Q

methods of winding armature & its applications

A

wave winding - low current, high volt

lap winding - high current, low volt

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10
Q

how does a carbon-pile voltage regulator work

A

as volt increase, carbon-pile decompresses, resistance increases, shunt field current drops, generator voltage drops

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11
Q

how does reverse-current-cut-out relay works

A

it will disconnect the generator from the battery when V gen < V batt

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12
Q

purpose of current limiter

A

protect generator from excessive loads (prevent overheating)

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13
Q

generator control unit components and its order of placement

A

from generator:

1) voltage regulator
2) current limiter
3) reverse current cutout relay

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14
Q

requirements and considerations in designing electrical power distribution system

A

1) power-consuming equipment must not be deprived of power in the event of power failure unless total power demand exceeds available supply
2) faults on the distribution system should have minimum effect on systems
3) power-consuming equipment faults must not endanger supply of power to other equipments

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15
Q

advantages and disadvantages when generators are connected in parallel

A

adv:
no break in supplies if a generator fails
share loads equally to improve life expectancy

disadv:
additional circuits are required to ensure both machines share equal loads

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16
Q

3 services of the busbar

A

1) vital/critical services - required during emergency (fire extinguisher, etc)
2) essential services - required to ensure safe flight in emergency situation (autopilot)
3) non-essential services - can be isolated in an in-flight emergency (IFE)

17
Q

difference between ac motor and dc motor

A

ac motors has no commutator (brushes & slip rings)

speed of ac motor is determined by frequency (dc has no frequency)

18
Q

dc generator vs dc motor

A

dc motor converts electrical energy into mechanical energy

19
Q

series wound motor characteristics

A

high starting torque
never run without a load
can be started on full load

20
Q

shunt wound motor characteristics

A

constant speed
torque is proportional to armature current
must be started on light or no load

21
Q

compound wound motor characteristics

A

good starting torque and stability in speed

provides benefits of series and shunt wound

22
Q

which dc motor can be started on a full load?

A

series wound motor

23
Q

which dc motor can be started on light or no load?

A

shunt wound motor

24
Q

what is a starter generator

A

single component starter and generator

25
Q

advantages and disadvantages of starter generator

A

adv:
save size and weight
only 1 mechanical drive needed

disadv:
generator output is difficult to maintain at low engine rpm

26
Q

4 aircraft power sources

A

ram air turbine
auxiliary power unit
ground power unit
battery cart

27
Q

colours of the position lights

A

green - starboard (right)
red - port (left)
white - tail (stabilizers)

28
Q

2 types of anti-collision lights

A

rotating beacon (red), strobe light (white)

29
Q

rotating beacon light is required to operate when?

A

the engine is still running

30
Q

2 types of landing lights

A

fixed; retractable

31
Q

3 types of internal lighting

A

cockpit & instruments; cabin; cargo compartment

32
Q

purpose of armature winding in a dc generator

A

generate emf

33
Q

what rings are used in ac & dc generator

A

slip rings - ac generator

split rings - dc generator

34
Q

will main DC busbar charge the battery in flight?

A

yes

xxxAEIS (9 decks)

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