Flashcards
Electrical power powerpoint 4
Cards in this deck (28)
- 12 different components used for DC generationTRU and Batteries
- 2TRU- normally 1 for each main DC bus
- located in electrical compartments
- convert 3 phase 115v AC to 28v DC - 3TRU cont.consists of 2 main parts;
- Transformer (steps down 115v to 28v)
- Rectifier (converts AC to DC)
- 2 separate pairs of windings
- one of them winds primary and secondary in star form.
- the other set has the secondary connected in delta.
(Star to Star and Star to Delta)
- Star to delta helps give smooth DC with no ripples. - 4DC generation of TRU2 output parameters;
- - 5TRU failure protection2 types;
low current - indicates small internal fault when current falls below 2A
overheat - triggers when temp near rectifier exceeds limits. Indicates consumer overload or short circuit. - 6TRU overheat detection- when temp exceeds limit, a bimetallic switch closes
- contact of internal relay opens to disconnect TRU
- (indications on ECAM/CWS)
- when TRU is off, Bimetallic switch cools down and opens
- TRU remains off because relays are active still
- Needs to be reset.
- - 7TRU reset- done on ground after fault finding
- reset by either; Central Maintenance Computer or a Reset Pushbutton
- Normal parameter (eg. voltage) on ECAM give indication of good reset. - 8Aircraft Batteryused for;
-Emergency power
- APU start - 9Method 1 of battery installation- normally 1-3 batteries used for emergency power or APU start.
- number of batteries dependant on electrical requirements of aircraft. - 10Method 2 of battery installation- 1 battery for emergency power
- 1 battery for APU start - 113 types of battery- Nickel Cadmium
- Lead acid
- Lithium ion - 12Ni-Cad batteryadv over lead acid;
-less maintenance costs
- better performance at lower temp
They contain 20 cells
- produce 1.2v each (24v overall)
- connected in series
- reach 1.5v when charging
- when at 1v each they are discharged - 13Ni-cad cont.consists of;
- vent cap (regulates electrolyte level and releases any excess gasses)
- plate cap (pos and neg plates, large s.a, similar poles connected)
- separator (plastic, prevents a short between pos and neg plates. May melt and damage battery if too hot)
- electrolytic fluid (alkaline. levels rise during charge) - 14Ni-cad charging2 ways;
- 28v from DC distribution
- using separate power that uses power from AC distribution - 15Ni-cad requirements- must always be charged (recharged after use and trickle charge during operation)
- checked for maintenance every 2000 operating hours
- never allow overheat (eg. continued APU start)
- never allow discharge below 22v (switches polarity of weakest cell in battery so it cant be charged)
- check charge levels at intervals (monitor current and voltage) - 16constant current/voltage charging of Ni-cad batteries- quick safe charging
- increases output from 28v to max of 36v
- when fully charged it switches from current to volatge constant charging
- remains at 28v - 17Ni-cad battery charger unit.2 parts;
TRU - gives DC
OUTPU CIRCUIT - controls charging by 2 methods:
constant voltage/potential
constant current - 18Ni-cad BCU cont. -- also opens contacor when fully charged
- aso opens when discharged on ground (below 23v) - 19charging protection on ni-cadtemp switch (bimetallic) used that closes above 60 degrees celsius. - it switches off the charger.
- when it cools to operating temp the switch then opens and charging resumes. - 20Lithium ion battery- lithium cobalt oxide
- 8 cells
- 28v 75Amp/hours - 21lithium ion advantages over Ni-cad- high voltage and high current production
- improved power quality
- fast recharge
- 30% lighter
- compact
- no memory degradation - 22Lithium ion chargingcharged in 3 steps;
-constant current (charges to volt limit)
- balance (current reduces and brings each cell to same level)
- constant voltage - applies voltage equal to no. cells x cell voltage. (voltage applied until current falls below 3% of constant charge current) - 23Lithium ion battery requirements- don't charge below 0 degrees Celsius
- keep within voltage and current limits (to prevent thermal runaway or cell rupture)
- fail safe circuits installed which shut off when a cell is outside its 3-4.2v limit.
- - 24battery indicationsvoltage - ECAM and PCP
current - ECAM only
- voltage measured by hot battery bus
- current measured by shunt
SHUNT is a resistor that drops a voltage proportional to current. - 25Thermal runaway- output of ni-cad decreases when overheating (during charge)
- when this drops the current increases
- this causes more heat and voltage drops further (so current increases further) - 26Thermal runaway preventioninstall a battery charge limiter to;
- monitor charge current
- conactor opens on indication of thermal runaway
- this remains open unless manually reset on PCP - 27Ground powersupplied by;
- external power source
- APU generator
2 engine a/c: usually 1 APU or GPU will power consumers (never together)
4 engine a/c: may need another external power source - 28Connecting external power2 conditions must be met
- chocks in
- aircraft grounded
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- Flashcards on Electrical power powerpoint 4, created by Aiden Grocock on 14/12/2017.
- Created by
- Aiden Grocock · Dec 2017
- Updated
- Dec 14, 2017
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