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ATA 24 Electrical Power Flashcards

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1
Q

What is the priority of supply to the two normal buses (AC BUS 1 & AC BUS 2)?

A
  1. Onside generator
  2. External power
  3. APU GEN
  4. Offside generator
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2
Q

What allows the AC ESS BUS to be supplied by any generator or external power?

A

The 3XC contactor

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3
Q

What is the capacity and nominal voltage of the aircraft batteries?

A

23Ah

24V DC

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4
Q

What are the characteristics of the engine, APU and external power generators?

A
  • 115/200V, three phase
  • 400 Hz
  • 90 kVA
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5
Q

What are the characteristics of all TRs?

A
  • Maximum output of 200A
  • 28V DC
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6
Q

What normally supplies DC ESS BUS?

A

DC BAT BUS

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7
Q

What are the characteristics of the emergency generator?

A
  • 115/200V, three phase
  • 400 Hz
  • 5 kVA
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8
Q

On battery power only, what is battery 1 connected to?

A

AC STAT INV BUS

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9
Q

What are the characteristics of the static inverter?

A
  • 115V, single phase
  • 400 Hz
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10
Q

Which busbars are shed in battery only configuration?

A
  • AC ESS SHED BUS
  • DC ESS SHED BUS
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11
Q

Within the GCUs, what energises the Generator Line Contactor relays?

A

Power Ready Relay becomes energised

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12
Q

Within the GCUs, what energises the Bus Tie Contactors, allowing reconfiguration of the AC supply network?

A

BTC lockout

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13
Q

Through what component does the GPU supply ground services power to the DC GND SER BUS, in addition to the AC GND SER BUS?

A

TRU2

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14
Q

What is meant by transient configuration with regards to aircraft power?

A

While the RAT is extending or there is no emergency generator as yet, battery 1 will supply AC ESS BUS through the STAT INV, while battery 2 will supply the DC ESS BUS

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15
Q

What conditions must be met for the emergency generator to supply power?

A

Aircraft speed over 100 knots

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16
Q

When the aircraft drops below 100 knots, what occurs with regards to aircraft power?

A

Batteries connect (BATT 1 to AC ESS, BATT 2 to DC ESS)

AC ESS SHED and DC ESS SHED are disconnected

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17
Q

When the aircraft drops below 50 knots, what occurs with regards to aircraft power?

A

AC ESS is disconnected from static inverter but static inverter bus is still supplied

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18
Q

What is the implication for ground service power if TRU2 is unserviceable?

A

Ground services switch will not latch on, and therefore ground services are unavailable

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19
Q

How are AC and DC busbars labelled?

A

AC - XP

DC - PP

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20
Q

What numbers are reserved for 26VAC supply buses?

A

Thirties

Eg. 131XP-A

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21
Q

How are ARINC429 buses identified?

A

ATA 100 prefix and then numbered between 7000 and 7999

Eg. 36-11-7072

36 - chapter
11 - sub chapter
7072 - shielded cable number

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22
Q

What would the letters IW tell you about a component?

A

It is a ‘virtual’ busbar because the circuit breakers are connected directly to the power source

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23
Q

What is the smoke configuration of AC supply system?

A

Both bus tie contactors are open to isolate one side of the network from the other

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24
Q

What is the warning with regards to the red guarded MAN ON pushbutton?

A

It will deploy the RAT even on a cold aircraft

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25
What component acts as the interface between the GCUs and the CFDIU for test purposes and fault reporting on the MCDUs?
GAPCU
26
Where are the GCUs and the GAPCU located?
90VU
27
What conditions must be met for the GCU to regulate the output speed of the IDG?
* GCU is powered up * Engine input speed to the IDG is sufficient for speed control to begin * No failure is present in the channel to trip the servo valve control circuit
28
Which components for the aircraft power system are located in the left lateral avionics bay?
* Emergency GCU * Essential TRU
29
Describe the servo valve control loop?
GCU circuitry monitors permanent magnet generator frequency to determine generator frequency This frequency is compared to an internal reference frequency Error signal causes a current to flow in the servo valve, oil is then ported to a hydraulic cylinder which determines the position of a variable displacement hydraulic unit The output of this hydraulic unit is summed with the incoming gearbox speed to give the desired speed
30
What is the desired speed of the generator within the IDG?
24000 rpm
31
What provides the GCU with engine speed information?
FADEC
32
Where are the oil temperature sensors on the IDG?
* IDG oil inlet port * IDG oil outlet port
33
What happens at the various stages of oil temperature at the IDG outlet?
142°C - Advisory mode on the lower ECAM 185°C - Master caution triggered and manual disconnection instruction written on the ECAM 200°C - Automatic IDG disconnection due to solder fuse melting
34
When will the Differential Pressure Indicator (DPI) on the IDG oil filter scavenge filter pop out become activated?
50 ± 8 psi
35
In the IDG charge oil circuit, at what pressure does the Low Oil Pressure (LOP) switch activate?
Below 140 psi
36
In the IDG charge oil circuit, when no underspeed condition exists, what will LOP switch activation cause?
Amber FAULT legend comes on on the IDG pushbutton ECAM warning is triggered
37
What must be done if overtemperature of the oil outlet or under pressure of the oil not caused by under speed is detected in the IDG?
IDG must be disconnected by the solenoid activated clutch
38
How is the IDG reset after the clutch mechanism has been disconnected manually?
Pulling the reset ring on the IDG casing with aircraft on the ground and no engines running
39
Describe the AC generator portion of the IDG?
Three-phase, brushless, spray oil cooled unit
40
What are the CT used for?
Two 3 hole CTs are used for differential current, overcurrent and overload One 6 hole CT is used for open circuit protection
41
Describe generator operation from the GCU point of view when the GEN P/BSW is pressed in?
1. Generator Control Relay closes 2. Generator is excited 3. When all parameters are correct the PRR closes 4. Power is connected to the Generator Line Contactor
42
Where is the point of regulation of the IDG circuit?
Between the generator and GLC
43
What does the GCU monitor the three phase voltages from the generator at the POR for?
* Voltage regulation control * Over and under voltage protection * Incorrect phase sequence protection
44
What occurs within the GCU if any parameter is incorrect, indicated by the FAULT legend coming on?
GCR, PRR and GLC all open SVR will also open if the fault is frequency related
45
When will the fault legend show on the IDG generator?
* Any parameters are incorrect * Related engine is shutdown or the generator is not connected * GLC has failed open
46
What inhibits a manual IDG disconnection with the engine stopped?
Underspeed protection generated by the GCU
47
How can a static test of the IDG disconnect mechanism be carried out with the engine stopped?
The circuit breaker 2XU1 must be pulled to simulate a running engine 1 and no underspeed
48
What are the users of the oil in the IDG?
* Generator * Differential gear * Hydraulic trim unit * Servovalve
49
Why is there an oil cooler bypass valve in the IDG?
In low oil temperature conditions, the oil pressure increases due to high oil viscosity
50
What classification of fault is the oil IDG outlet temperature sensor?
Class 3 - No flight deck effects are presented
51
What are the power supplies for the GCUs?
Main - PMG from IDG Backup - Battery bus
52
What are the main functions of the GCU?
* Regulation of voltage, frequency and speed * Control and protection of the network and the generator * Interface with SDACs, FADEC and CFDS
53
What does the GCU interface with?
* Engine fire pushbutton switch * Both SDACs for the ECAM monitoring * CFDIU through the GAPCU * FADEC which gives engine speed information
54
What information can be supplied to the GCU by pin programming?
* Aircraft type * GCU position * Current limit for voltage regulation * Load limit
55
What happens in the GCU if the FADEC signal for under speed is absent?
A back-up signal is provided from the engine master switch to inform the GCU logic that the engine will shut down
56
At what voltage will the overvoltage protection trip in the GCU and which relays trip?
130 ± 1.5 volts PRR and GCR
57
At what value of frequency will the GCU over frequency protection function and what relays trip?
435 ± 1 Hz for at least 4 seconds PRR and GCR are tripped 452 Hz for at least 160 milliseconds PRR, GCR and SVR are tripped
58
When an overload is detected in the CTs, what does the GCU do?
GCU sends signals to the SDAC for an ECAM message Fault light on the GALY & CAB P/BSW is illuminated
59
Through what is the APU GEN connected to the power network?
APU GLC and the BTCs
60
What does a high oil temperature sensed at the APU oil outlet port result in?
Automatic shutdown of the APU via the ECB
61
At what oil temperature at the APU oil outlet port will the APU automatically shutdown?
185°C
62
What supplies the power to the GAPCU?
* APU PMG * EXT PWR * Battery bus as a back-up supply
63
When will the fault legend of the APU MASTER come on?
If the switch is pressed in, the APU is running above 95% rpm and one parameter is not correct
64
Which relays within the GAPCU will open if a faulty parameter of ground power is present?
* Interlock Monitoring Relay (IMR) * PRR
65
How is a short circuit indicated and sensed in the GAPCU with regards to external power?
Positive Temperature Coefficient (PTC) sensor senses the short circuit on the PRR output line Red PTC TRIP LED on the front face of the GAPCU comes on BITE message sent to the CFDS
66
What are the functions of the GAPCU?
* Over and under voltage * Over and under frequency * Over current * Overload * EXT PWR interlock * Incorrect phase sequence * Open cable or open/short circuit * EPC failure
67
When are the over voltage and under voltage protections triggered in the GAPCU and what are tripped?
130 ± 1.5 VAC, inverse time delay to trip IMR, PRR and EPC 10.5 ± 1.5 VAC, 4.5 second time delay to trip IMR, PRR and EPC
68
What databus does the GAPCU use to communicate to the GCUs?
Mil-STD-1553
69
Why does the GAPCU interface with the LGCIU1?
Enables communication in interactive mode between the GCU, the GAPCU and the CFDIU when the aircraft is on the ground
70
Under what conditions will you have a FAULT indication on the GALY & CAB P/BSW?
IDG1 overload, IDG2 overload or APU overload
71
When is galley power automatically shed on the ground?
When there is an APU overload
72
When is the maintenance test of the GAPCU carried out?
Only on the ground with the engine shutdown, and * Automatically at each GAPCU power-up * Manually from the MCDU
73
How do you test the emergency generation test on the ground?
Blue hydraulic system must be pressurised using the BLUE PUMP OVerRiDe P/BSW EMER GEN TEST P/BSW must be held in
74
What does the RAT MAN ON P/BSW on the blue hydraulic panel do?
Enables extension of the RAT for hydraulic power supply only
75
When is RAT manual activation used using the MANual ON P/BSW?
In case of CSM/G automatic control logic failure
76
What component is used to compare the speed of the PMG in the emergency generator for speed regulation purposes?
Quartz crystal controlled frequency reference
77
What type of CFDS system is the emergency generator and why?
Type 3 Only has a discrete input and output
78
What is the nominal power of the static inverter?
1 kVA
79
When is the static inverter used?
* APU start (supply of fuel pump) * Engine start on battery * Emergency configuration
80
Which component supplies the information that the aircraft is flying above 100 kts, 50 kts etc?
ADIRU1
81
What component monitors the static inverter faults, and what parameters are monitored?
BCL * Overheat * Output/input over voltage * Input under voltage
82
What is the time delay when 3XC1 switches over automatically to 3XC2?
3 seconds
83
How is a fault of automatic switching from 3XC1 to 3XC2 indicated?
FAULT legend on the AC ESS FEED P/BSW
84
What is the successive supply from the TRU1 in normal configuration?
DC BUS 1 DC BATTERY BUS DC ESS BUS DC ESS SHED BUS
85
How does the DC ESS BUS receive power where there is any failure of either TRU1 or TRU2?
Through ESS TRU
86
What protections are built into the TRs?
* Overheat protection * Minimum current flow
87
How can a TR be reset after a fault condition?
* MCDU via CFDIU * Guarded toggle switch located in the battery compartment
88
What is inhibited when only AC and DC ground service buses are supplied by external power, with regards to TR2?
Minimum current detection
89
Where does the fault signal for the ESS TR go?
FWC 1 and 2
90
How is the position of the BCL and aircraft type indicated to the BCL?
Pin programming
91
When is hot bus protection supplied for the batteries?
* Discharge current is greater than 100A for 300 ms * Discharge current is greater than 400A for 5 ms
92
When is thermal runaway or short circuit protection provided for the batteries?
* Charge current over 10A and increasing by more than 0.375A per minute * Charge current is greater than 150A for 90s
93
When is complete discharge protection provided for the batteries?
Battery voltage is lower than 23V DC for 15s, BCL supply contactor opens automatically
94
What is the purpose of the Electrical Generation Interface Unit (EGIU)?
Convert analogue and discrete signals from the GCU and GPCU into ARINC 429 data
95
What does EGIU1 and EGIU2 interface with, before sending fault information on to the SDACs?
EGIU1 - GPCU and GCU1 EGIU2 - APU GCU and GCU2
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