Electronics
T2a
T2a
Fichier Détails
| Cartes-fiches | 474 |
|---|---|
| Langue | Deutsch |
| Catégorie | Electronique |
| Niveau | École primaire |
| Crée / Actualisé | 12.01.2015 / 21.01.2020 |
| Lien de web |
https://card2brain.ch/box/electronics_
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What are teh advantages of NiCa batteries?
Even voltage before rapid discharge
If one of teh 12 cells of a Lead-acid battery has a broken connection rendering it ioperable, the battery:
is unserviceable
The purpose of bonding teh metallic parts of an aircraft is to:
a) ensure zero voltage difference between aircraft components b) provide a single earth for electrical devices
The conditions to be met to activate a shunt generator are:
a) presence of a permanent field b) minim. rotation speed => the initial power for the shunt-wounded gene is provided by the battery power connected to the field coils wounded around the pole pieces
The shunt wounded generator prodces an output in which:
the voltage decreases slightly with increase in load.
When a persistent over-excitation (Überreiz) fault is detected on only one AC generator, the protection device opens the:
exciter breaker and generator breaker
Because of the input/output relationship of an OR gate, it is often reffered to as the:
any or all gate
Th ecapacity of a battery is given in
Ampere hours
Electrical bonding of an aircraft is used to:
a) protects the aircraft against lightning effects b) Reduce radio interference on radio communications systems c) set the aircraft to a single potential
The essential difference between aircraft AC alternators and DC generators (dynamos) is that the:
induced (output) windings of the alternators are fixed( stator) and the dynamos have a foxed inductor (field) coil
Increase in frequency,at constant voltage and capacitance, will cause
an increase in current flow and a decrease in frequency will cause a decrease in current flow
The primery function of a constant speed drive (CSD) unit in an AC generating system is to:
drive the generator at a constant speed
If the electrical load of an AC generator providing a constant outpt voltage increases, the voltage regulator will
increase the excitation current
What is the purpose of the GCB (Generator Control Breaker)?
Connects generator to its busbar
A thermal circuit breaker:
protects the system in the event of a prolonged (anhaltenden) overcurrent
A ,,Zener" diode is used for:
voltage stabilisation
AC generators connected in parallel must:
a) be in phase
b) have the same coltage (within 10V)
c) Have teh same phase angle (within 90 Grad)
d) have the same frequency (within 3-5 Hz)
e) real and reactive load sharing must be effective
Alternator Rotor
Field current produce a magnetic field around the core=> the strength of the field current determines the strength of the magnetic field => DC => Only one direction brush and slip rings => Rotor is driven as the engine runs
Alternator Stator
three stator surround the rotor => stator is fixed => Because of the rotation of the rotor an AC is produced
When an underspeed over overspeed fault is detected on an AC generator connected to the aircraft AC busbar, teh protection device opens the :
generator breaker
usually in conductive materials:
the resistance increases with increasing temperature
Hot battery bus is connected directly to the
battery without any swichtes
Assuming a Constant speed Drive (CSD) fault is indicated, the CSD should be disconnected:
provided the engine is running
During start an engine fitted with a brushless AC generator with no commutator rings, the generator is activated by:
a set permanent magnets
A constant speed drive (CSD) unit is normally provided with means of monitoring teh following parameters during the flight
oil over temperature and low oil pressure
The measure output power components of a constant frequency AC system are:
kVa and kVAR
An AC generator driven by a contstant speed drive (CSD) unit:
requieres a voltage controller to maintain constant voltage under load.
GCU's ?
Generator Control Unis: are used for the purpose of MONITORING the generator output parameters, Sometimes also generator voltage regulation functions => will detect faults and
open the Generator Control relay = interrupts the titer current and thus de-energize teh genator field and also Open Generator Circuit Breaker = disconnects teh faultly generator from the busbar
An AC generator, it can be said that (GCU)
a) Modern GCUs are provided with a permanent indication to record the failure b) All the commands originating from the control panel are applied via the GCU except dog clutch release
Synchronous field speed = RPM => Formel
(frequency in HZ x 60 )/ number of pole pairs !! a 4 pOle => 2 pole Pairs !!
In an AC power generation system the constant speed drive (CSD):
In in the event of an AC generator fault, on a twin engine aircraft, the protection device will open:
the exciter control relay and the generator breaker
The current in a DC circuit, according to OHM's jaw, can be described as:
inversely proportional to the resistance and directly proportional to the voltage.
An aircraft electrical circuit which uses teh aircraft structure as a return path to earth, may be defined as a:
single pole circuit
On board typical modern aircraft, the batteries used are mainly Ni-Ca. Their advantages are:
A) good charging and discharging capability at high rating B) wider permissible temperature range C) good storage capability D) sturdiness (Festheit) owing to its metal casing
The function of the generator breaker is to close when the voltage of the:
generator is greater than battery voltage and to open when the opposite is true.
Frequency wild AC system only for
light aircraft and turboprops => cannot be parallel => The generators are not rotated by the engines at a constant speed => They do not employ any CSD units = rotational speed of the generator is dependent on the rotational speed of the engine
Frequency wild in relation to a AC generation system means the generator:
output frequency varies with engine speed
How are the loads on an aircraft busbar connected?
In parallel so that current through the busbar reduces as loads are switched off
Real load sharing in a parallel AC system is achieved by:
automatic adjustment of the torque on each generator rotor via the CSD unit
