Exam 1 Big Review Flashcards
Left hand rule
thumb points with current, fingers show magnetic field
left hand rule (generators)
thumb shows force direction
index for magnetic field
middle finger for direction of current
conductor
gives atoms, nearly empty shell
insulator
takes atoms, nearly full shell
Control device
controls flow of current
power producer
produces current
power consumer
uses current
resistors have what purpose
stop current to maintain stable resistance in various environments
transformer
increases or decreases AC voltage in a circuit
relay disadvantages
big heavy, slow, uses a lot of power
solenoid advantages
stronger, carries higher current
point of shielded wire
shields electrical interference - used for audio signal and high frequency
why is solder flux used
prevents oxidation in solder
wet cells are used in
aircraft, automotive, standby telecommunications
VRLA battery advantage
low maintenance, cannot spill
Gel Cell usage
acrobatic aircraft
gel cells
recombinant battery (produces water) but needs pressure relieve valve
lead-acid battery usage
smaller aircraft
lead-acid battery characteristics
less expensive, bad power to weight ratio
nickle cadmium battery usage
turbine aircraft
nickel cadmium battery advantages
greater power to weight ratio
closed circuit voltage (near constant until dead)
lithium ion battery usage
portable electronics
lithium ion battery advantages
no memory effect, best weight - energy ratio, higher voltages
potential problems with lithium ion batteries
thermal runaway
generator armature
rotates
carries current
generator field
stationary
magnetic field
generator commutator
changes AC to DC
generator brushes
electrical contacts allowing current path for power to leave
alternator field
rotates, creates magnetic field
alternator armature
stator, produces voltage
alternator rectifier
changes AC to DC with diodes
3 Phase power advantage
constant power supplied
provides greater power density at same amperage
smaller wires, lighter load, lower cost
why is Alt > Gen
lighter, cheaper, more reliable, less maintenance needed
what does a regulator do
controls field strength to keep generator output at necessary volt/current for variable load
regulator inputs
mechanical / electrical energy
regulator output
voltage / current from armature
vibrator regulator
older, uses electromagnet
regulator transistor advantages
cheaper, lighter, more reliable, longer MTBF
smaller input controls larger output
uses control valve
zener diode
voltage sensitive
controls transistors
no moving parts
load meter
measures alternator current
starts at zero
shows load on alternator
ammeter
zero in center, shows charging rate
series
one current path
constant CURRENT
parallel
more than one current path ( divided flow )
constant VOLTAGE
DC current usages
batteries, portable/movable systems
CONSTANT POLARITY
AC usages
houses, large aircraft
POLARITY CHANGES
rectifier
AC to DC
inverter
DC to AC
(complex and expensive)
DC advantages
portable
backup power
starts engine
AC advantages
easily converted
three phase gives more power
single wire used
in metal aircraft
two wire used
in composite aircraft
which type of aircraft needs a ground conductor
composite aircraft
Bus hierarchy
most important bus least likely to lose electrical power
hot battery bus always connected to battery
