11.6 Flashcards by William Thomas

What is the voltage available on aircraft?

28 VDC
115 Vac / 200 400hz
24 vac on battery

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How is electricity generated on aircraft?

IDG integrated drive generator

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How is DC current generated?

Through the (TRU) transfer rectifier unit

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What are the different types of power generation available?

APU auxiliary power unit RAT ram air turbine GPU ground power unit

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How long must a battery be able to supply sufficient power?

30 mins

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How is DC to AC power conversion done on aircraft?

Through a static inverter

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What is the meaning of battery rating and figures?

12 (v) volts 60 (atm) amp hours

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What are the two types of electronic power generation?

Dc and Ac

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What is the main aircraft battery type?

Nickel cadmium 24vdc

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What is the battery capable of providing?

-starting the engines
-supply to essential consumers
-general stabilises dc bus bars

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What is the design of battery venting?

Rubber or other non corrosive pipes vent to fuselage skin, lead acid type have an acid trap

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What is common practice when securing quick release connectors for batteries?

Using copper lock wires

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How much voltage does a single cell produce and how are they connected?

1.2 volts connected in series for a complete voltage of 24 volts

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During charge and discharge what will be the voltage?

During charge 1.5 v
During discharge 1.0 v

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When / how often would a workshop condition check be performed?

Every 2000 flying hours

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What precautions should be taken to ensure reliable battery operation?

-never attempt repeat apu starts the battery may overheat
-do not discharge battery below 22v
-line maintenance personnel must check charge level at standard intervals

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What is thermal runaway?

Effectively a series of knock on effects lead to an explosion

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What are the two types of battery charging?

-constant voltage
-constant current

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What capacity must testing achieve on a battery?

80%

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What are the advantages of a lithium ion battery?

-high voltage and high current production
-improved power quality
-ability to recharge quickly
-30% less weight than nic-cd
-no memory degradation

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What is a dc generator required to provide?

a constant voltage with set limits
a full range of engine speeds idle to take off
no loads up to full load
to share the load with other generators or multi engine aircraft

What is a paralleled system?

When the load is shared between IDG’s and the equalising coils detect output to ensure equal output from IDG

What is load shedding?

Off loading high energy consumption systems

What are the sources of AC power?

Ac generator
Static inverters
Rotary inverters

What is AC electrical power supply on aircraft?

Three - phase 400 hz 115/200v

What is a rotating field generator?

A stationary armature with a rotating field with no change in flux direction, the magnetic field is either permanent magnetic or dc wound coil

What is the AC generator frequency directly proportional to?

The rotational speed of the rotor

Why are modern aircraft powered by constant frequency systems?

-lighter -can be operated in parallel -suitable for wider range of loads -generator loading does not vary with engine speed -loads are designed for optimum efficiency -induction motors operate at a constant speed

What is a constant speed drive?

It takes the variable speed of the engine and creates a constant speed

What do modern civil aircraft typically use in terms of generators?

Three phase brushless generators

Where is the constant speed drive installed?

Between Auxiliary gearbox and the generator

What is the function and design of the oil circuit on a CSD?

An internal oil circuit used as hydraulic fluid for the motor pump, cooling and lubrication

What is underspeed?

When CSD input speed drops below normal control range, the CSD cannot maintain the output This occurs at 5% below engine idle

What is underspeed?

When CSD input speed drops below normal control range, the CSD cannot maintain the output This occurs at 5% below engine idle

What is the purpose of CSD disconnect?

Decouples input shaft from input spline shaft in transmission malfunction

What is the purpose of CSD disconnect?

Decouples input shaft from input spline shaft in transmission malfunction

What is disconnect verification?

ECAM/EICAS check for zero voltage if done

What is disconnect verification?

ECAM/EICAS check for zero voltage if done

What is an IDG?

Integrated drive generator A state of the art generator Generator and CSDU in one

What are the functions of generator control units?

-Voltage regulation -current limiting -protection from out of tolerance voltages -frequencies crew alerting

What is a current transformer?

Amp clamp Three inductive pick up coils that provide current sensing signals

How many revolutions are needed on a 1 or 2 pole pick up for the same frequency?

With 2 pole pairs it will only need to spin half as often

What are the circuit protection devices?

Fuses and circuit breakers

What does a circuit breaker or fuse do?

Prevent currents higher than the max AWG

Where is the only circuit that a fuse or circuit breaker is not needed?

Generator feeder lines

What is more commonly used over fuses?

Circuit breakers

What are the types or circuit breakers?

Push/ pull Pulse Switch Thermal

How many times can a circuit breaker be reset during flight ?

Once if necessary

What is common when tripping circuit breakers?

Gagging and an entry into the tech log

What are the 6 pins on ground power plugs?

Phases A,B,C, neutral, 2 interlock the e & f which are shorter