11.6 elec power Flashcards
where is electrical heating used
galleys, anti ice, water, cockpit windows
what does the electrical power system consist of
generation, distribution
what are the electrical generation subsystems
AC/DC
what are the 3 different DC power sources on modern aircraft
DC battery, DC ext power, DC generators
what is an aircrafts battery used to supply
emergency power, APU starter motor power
what type of battery is the main battery
nickel cadmium type
what power does the main battery supply
24v DC
whats the EPU
external power unit
whats the power source during flight
engine driven generators
how many AC generators does each engine have
one or more
does the aircraft battery provide power in flight or ground
ground
batteries provide power by converting what
chemical energy into electrical
in an emergency how long will the battery supply power for
30 minutes
how are batteries vented
pipes
whats used to prevent reverse flow in the ventilation system on ground
non return valve
why is copper lockwire used to secure the battery connector
can quickly disconnect without wire cutters
what are the 2 types of aircraft main battery
Ni-Cd, lead-acid
during charging what is the individual cell voltage
1.5v
during discharge what is the individual cell voltage
1v
when are workshop checks carried out on batteries
2000 operating hours
what is one of the most major problems with batteries
thermal runaway
what are the 2 basic ways of charging batteries
constant voltage, constant current
what batteries is constant voltage charging method generally used on
lead-acid batteries
what type of batteries use the constant current charging method
Ni-Cd batteries
in a battery test how long must a battery provide all necessary power for if failure occured
30 mins
in battery tests what capacity do batteries require
80%
what are the 2 different methods used to recharge NI-cd batteries
28v from DC VIA TRUs, separate battery charging unit
what do AC powered aircraft require to be installed
battery charging unit
why dont we usually charge batteries from ground power
can easily overcharge batteries
what does MFD stand for
multi function display
what battery parameters are shown on the cockpit display
voltage, current
when disconnecting a battery from an aircraft what lead do you disconnect first
negative lead
when installing a battery to an aircraft what lead do you install last
negative
list the advantages of lithium ion compared to Ni-Cd batteries
high voltage/current, improved power quality, recharge quickly, less weight, compact
what stages are lithium ion batteries charged in
constant current, balance, voltage source
lithium ion batteries have a fail safe feature that cuts the circuit out at what voltage
3-4.2v per cell
lithium ion cells cannot be charged safely below
0 degrees celcius
what are the 3 different sources of DC power
DC battery, external, DC generator
what type of battery is a DC battery
nickel cadmium
what voltage does a DC battery supply
24v DC
how many DC engine driven generators are there per engine
1
how are DC batteries cooled
duct air or internal fan
what are DC battery cores made from to prevent high altitude deformation
molybdenum disulphide
a DC supply needs to provide constant voltage in what 3 conditions
engine speed change, no loads/full loads, share loads with generators
what does the average DC starter generator weigh
10kg
what is the normal RPM range for DC batteries
7000 - 12000 RPM
what methods are used to attach AC and DC generators to engines
flange mounting, manacle ring
where is the generators direction on rotation shown
on ident plate
what is the purpose of a TRU
transfrom AC voltage to a DC voltage
what does a parallel system consist of
two or more generators connected to a common power bus
what does PPDS stand for
parallel power distribution system
what are all relays controlled by
GCUs
what are the advantages of parallel DC operation
TRUs loaded with average current, no DC bus lost when TRU fails
when is the main DC power isolated
when a TRU fails
what does the essential power distribution consist of
AC and DC part
how does the systems know when an engine has started
the engine RPM is higher than the starter motor can reach
what does airbus use for electronic controls in the cockpit
ECAM
what does boeing use for electronic controls in the cockpit
EICAS
on the elec sys control panel how many controls does each generator have
1 with an ON, OFF, RESET
what are the 3 sources for AC power
AC generators, static inverters, rotary inverters
what is the power of AC electrical power on aircrfat
400Hz 115/200 V
in a rotating field alternator the rotating magnetic field can be
permanent magnet, DC wound coils
in the rotating field alternator is there an electrical connection between the rotor and stator
no, only magnetic
what is voltage proportional to
speed
in AC power is rotational speed of the rotor increases what also increases
induced EMF
the frequency of the alternating output of a generator is directly proportional to what
rotational speed of rotor
how are AC generators output kept at a constant speed
by using a constant speed drive
in the internal oil circuit what is the oil used for
hydraulic fluid for motor pump, cooling, lubrication
in the external oil circuit what is the oil cooled by
oil cooler
what 2 ways is the CSD monitored in
by circuits, by indicators
what are the 2 CSD temp indicators
absolute oil temp, rise in temp
what is the only consequence of under speed AC CSD
stops generator delivering correct frequency
when disconnecting the CSD what do you check on the ECAM, EICAS displays
voltage and freq is 0
when must disconnect resets be carried out on the CSD
on the ground
why must the CSD be reset before engine starts
prevent damage to the IDG
to reset the CSD how long must the button be held from and how often
3 seconds held for and no more than once every 60 seconds
what does IDG stand for
integrated drive generator
what does the IDG do
create AC power
whats the frequency of aircrafts electrical supplies
400 Hz
what are the 2 basic types of inverters
rotary, static
what is a GCU
generator control unit
what are the 3 functions of the GCU
regulation, protection, switching
what does the GCU regulate
generator output
AC generation systems have what 3 basic forms
non-parallel, parallel, frequency wild
what form of AC generator system is the variable speed constant frequency
frequency wild generator
are non parallel or parallel systems more complicated
parallel more complicated
on DC powered aircraft where is AC power derived from
static inverters
what is a CT
current transformer
when cables pass through a current transformer, is there a physical connection between the cable and transformer
no
