Skyblue CBT electrical system Flashcards
what does the electrical system consist of?
- main battery
- emergency battery
- 2 engine driven DC starter generators
-2 AC wild generators
what do the static inverters do?
convert DC power to AC power at a constant frequency
what do the static inverters power?
the respective AC bus
what does the TRU do?
converts 115V AC from the AC wild gens to 28v DC in order to power the DC electrical system
what does the bus tie contactor do?
connects the tight and left electrical networks in the event of a failure
What page on the MFD shows the ACW system?
ACW/hydraulic page
what controls the AC and DC system logic?
2 Bus power control units (BPCU’s)
one for AC and one for DC
How does the BPCU control the electrical systems config?
- ACW BUS TIE contactors
- DC BUS TIE contactors
- load shedding through utility bus contactors
- AC and DC EXTERNAL power contactors
- ACW service bus contactor
- DC service bus contactor
what usually powers the DC system?
2 engine driven generators or external power
what is the purpose of the battery?
to power DC when not connected to ground power or with engines not running
what buses make up the DC system?
DC BUS 1
DC BUS 2
DC STBY BUS
DC EMER BUS
DC ESS BUS
HOT MAIN BAT BUS
HOT MAIN EMER BUS
UTIL BUS 1
UTIL BUS 2
GND HDLG BUS
What usually powers DC buses 1 and 2?
their respective starter generator
what powers the DC STBY BUS?
BUS 1 via the HOT EMER BATT BUS and DC EMER BUS
what happens if one of the batteries has a thermal runaway?
battery charge contactor will openand associated systems will be transferred to DC BUS 1
If BUS 1 is not powered, then a bus transfer contactor will close which will cause the associated bus to be powered by DC BUS 2
what powers the DC EMER BUS and DC standby buses if BUS 1 is offline?
ACW via the TRU
if the TRU is not running then power is from the HOT EMER BATT bus
what normally powers the DC ESS BUS?
DC BUS 2 via the HOT MAIN BATT BUS
What powers the ESS BUS if the battery has a thermal runaway?
DC BUS 1
or DC BUS 2 through the main bus transfer contactor
what powers non essential loads in the DC system?
2 utility buses
what powers the utility buses?
their respective DC bus through a utility bus contactor
what controls the utility bus contactors?
BPCU
when are the utility buses automatically shed by the BPCU?
when there is an overload of the DC system
how many volts are the MAIN and EMER batteries?
24v
how many amp hours are the 2 batteries rated for?
MAIN: 43
EMER: 17
what are the functions of the main battery?
engine starting and emergency power
what are the functions of the emergency battery?
ensures that emergency electrical network is powered even if main battery is depleted
prevents power transients on critical equipment during engine starts
what does the MFC do for the batteries (3)
- monitors battery charge
- connects the battery to DC BUS for charging
- PREVENTS THERMAL RUNAWAY
when are the HOT buses operating?
whenever the associated battery is charged
what powers the HOT buses under normal conditions?
DC BUS 1 and DC BUS 2
how is battery voltage and current checked?
maintenance panel on captains side
info is read from associated hot battery bus
what connects the ground handling bus to the HOT MAIN BATT BUS?
BATTERY TRANSFER UNIT (BXR)
when will the battery transfer unit (BXR) close?
- cargo door operating panel opened
- refueling panel access door is opened
- entry door is opened
how is the ground handling bus powered with external power?
BXR is opened and the external ground handling relay (EGHR) is closed which powers the ground handling bus through the DC service bus providing the DC GND SVCE bus is selcetd on from the cabin crew panel
what does the GND HDLG BUS power?
- cargo door control and indicators
- fueling control and indicators
- entrance light
what does the DC service bus power?
- Galley
- aircraft lighting
- lavatory system
- auto feather pump manual control
what powers the DC service bus?
DC bus 1 or external power
where do we connect the dc service bus to external power?
the DC button on the flight attendant panel if external power is connected
how is the service bus connected to external power?
DC servcie bus relay
how is the DC service and utility bus powered if its connected to BUS 1?
DC SVCE/UTLY BUS button on cockpit overhead panel
this overrides the cabin button
if the battery toggle switch is on in basic mode, what does the main battery supply?
- hot main battery bus
- DC essential bus
DC STBY BUS
Inverter 1
in basic mode, what does the HOT EMER BATT bus power?
DC EMER BUS
how is bus 2 powered when connected to external power?
through the bus tie contactor (BTC)
how is power for the inverter 1 transferred from the hot main batt bus to bus 1 when bus 1 is energised?
static power override contactor closes and hot main battery transfer contactor opens
what do the BAT CHG buttons allow?
charging of the batteries through external power
how does the power source for the DC STBY BUS change when connected to external power?
standby bus transfer contactor takes power from the HOT EMER BATT BUS instead of the HOT MAIN BAT BUS`
what happens when DC BUS 1 is powered by a generator and external power is disconnected?
- service select bus relay closes and service bus transfer relay opens
this transfers the source from external power to DC bus 1
what drives the DC generators?
associated engine accessory gearbox
what voltage does the DC GEN provide?
27-31 volts with a nominal output of 30
what is the nominal power output of the DC GEN?
12 KW
how are the DC generators cooled?
air cooled
what does the start contactor do?
connects the generator to the battery, dc external power of the opposite generator during engine start
what do the battery charge contactors do during start?
isolate the batteries from their respective buses in order to prevent power transients during start
what powers the DC stby bus during start?
hot emer battery bus
what powers inverter 1 during start?
hot main batt bus
during a cross start, when will the starter bus connect to the opposite side generator?
10% NH
when does the starter genratro stop cranking the engine during a cross start?
45% NH
when during start does the starter generator act as a generator?
61.5% NH
what controls the transition from starter generator to generator during start?
generator control unit (GCU)
what does the GCU do during start transition from Starter gen to generator?
opens start contactor at 45% NH
closes genrator contactor at 61.5% NH
what 8 issues does the GCU provide fault protection and detection for?
- over or under voltage
- over or under speed
- differential fault current
- generator overload
- power and fault current limiting
- bus tie lockout
- reverse current
- equalising load
how does 1 generator power both sides of the system?
by going through the closed bus tie contactor
when will the bus tie contactor automatically open?
when both generators are online after start
what does the AC system consist of?
a 26v network
a 115v network
2 inverters
what DC voltage do the static inverters require to operate effectively?
18-31 DC
what frequency does the AC system work in?
400hz single phase
what does AC bus 1 115V power?
- electrical power
- indicating and recording
- navigation
- pneumatic
what does AC STBY BUS 115V power?
- fire detection
- ice and rain protection
- indicating and recording
- lights
what does AC BUS 2 115V power?
- air conditioning
- electrical power
- indicating and recording
- lights
- navigation
what does AC BUS 1 26V power?
flight controls
navigation
what does AC STBY BUS 26V power?
flight controls
indicating and recording
navigation
what does ac bus 2 26v power?
naviagtion
what will happen automatically in the event of an inverter failure?
AC BUS TIE relay closes and links the 2 115V AC buses`
what happens in the event of an inverter 1 failure?
AC STBY BUS automatically switvhes over to be powered by AC BUS 2
what powers the AC wild system?
2 engine driven brushless ACW generators
what is the delivery voltage of the ACW system
20 KVA
what is the power range of the ACW system?
115-200V
what is the frequency range of the ACW system?
341-488Hz
what does the ACW GCU provide protection and detection for? (9)
- overvoltage
- undervoltage
- power and fault current limiting
- bus tie lockout
- differential fault protection
- over frequency
- under frequency
- open phase
- voltage regulation
when will the ACW GCU open a contactor?
when a fault has been detected
how are the 2 ACW buses connected in the event of an ACW gen failure?
2 contactors are closed linking the 2 buses to be powered by the remaining ACW GEN
how is external power connected to the ACW system?
EXT power button on overhead ACW panel
ground power will now take priority over the ACW generators and their connectors will be opened
what powers the ACW service bus?
ACW BUS 1 or external power (pushbutton to connect in cabin)
when is the ACW service bus shed?
when one ACW generator is offline
in the event of a double DC generator failure, what will the TRU power using the ACW system?
- DC STBY BUS
- DC EMER BUS
- DC ESS BUS
INV 1
what will the DC generator do if it senses an underspeed condition?
BTC will close, and the generator will reconnect itself automatically once its back up to speed
(if any other GEN fault occurs we need to reset manually)
when will a SHED CAPTION and caution bell sound?
when an overload is sensed. at least one utility bus will then be isolated
when will the MFC open the battery charge contactors?
- thermal runaway
- if associated dc bus voltgae is less than 25v
- if batter toggle swtich is in overide
- during engine start
when will MFC close battery charge contactors during start?
when start selector is out of the start or crank position
when will a FAULT show on the battery charge push button?
if an overheat is sensed (150C)
if the charge contactor fails do operate
what happens if battery toggle swtich is on when connected to external power or the genrators?
HOT EMER BUS powers:
- DC EMER BUS
- DC STBY BUS
HOT MAIN BAT BUS powers:
- DC ESS BUS
WHAT ARE THE only powered buses with no connected power and the battery toggle switch off?
HOT EMER BATT BUS
HOT MAIN BAT BUS
what does the override toggle switch position do?
keeps the DC system in basic mode in the event of double DC failure
when does the undervoltage caption on the stby bus button illuminate?
DC STBY BUS voltage less than 19.5V
what happens when the STBY BUS override button is pushed?
DC STBY BUS and inverter 1 are powered by the source that is powering the DC EMER BUS
what happens when the STBY BUS override button is pushed in order to release?
DC STBY BUS and INV 1 will be powered by the source that powers the DC essential bus
what does turning the TRU button do?
TRU draws power from ACW BUS 2 and provides DC to:
- DC EMER BUS
- DC ESS BUS
- DC STBY BUS
- INV 1
when will an inverter fault happen?
undervoltage or overvoltage (less than 102 or greater than 123)
what powers the inverter 1 when override is in the normal position?
the same source what is powering the DC ESS BUS
INV 1 will also power the AC STBY BUS
what powers INV 1 when the override button is pressed?
the same source as what is powering the DC EMER BUS
INV 1 will also power the AC STBY BUS
what voltage does inverter 1 require for normal operation?
18 volts
when will an ACW generator reset itself automatically?
after an NP overspeed of 3 seconds or less
generator underspeed
what does he ACW BTC operating selector on the captains side allow?
maintenance to force open the ACW BTC
at what voltage will the emergency bus box on the elec page go amber?
18v
