2 BatteriesA device composed of one or more cells in which chemical energy is converted into electrical energy.The most commonly used storage battery for aircraft is the lead-acid battery.
3 Batteries Lead-acid Batteries Used for Starting engines and supplying power in the event of generator failure.Stabilize and smooth out the generator output during extreme load changes.12 volt or 24 volt batteries are available.
4 Batteries Battery Ratings Voltage Voltage of any battery is always a function of its state of charge and current load placed on the battery.The number of cells in a battery determines the voltage it will produce.
5 Batteries Battery Ratings Ampere-hour Capacity The area of the plates, the amount of active material in the plates, and the amount of electrolyte determine the ampere-hour capacity of the battery.The capacity is a measure of the battery’s ability to produce a current flow for a specified time.
6 Batteries Ampere-hour One ampere-hour of capacity is the amount of electricity that is put into or taken from a battery when a current of one ampere flows for one hour.Any combination of flow and time that moves the same amount of electricity is also one ampere-hour.
7 Batteries Rated capacity Indicates the battery’s ability to perform when it is new.What determines the battery’s actual capacity?
8 Batteries Actual capacity depends on: Battery temperature Battery state of chargeBattery condition
16 DC Generator Disadvantages All of the AC load current is produced in the rotating armature of a generator.The AC must be changed into DC by the commutator and brush assembly.The brushes and commutator typically require regular maintenance.
18 DC Alternators Generate AC in their windings. Before the AC leaves the housing it is converted (rectified) into direct current.The rectifier of an alternator is made up of six silicon diodes.
19 DC Alternators Advantages The load current is generated in the stator or stationary winding and does not have to flow through brushes.
20 DC AlternatorsThe coils in the stator are connected as three windings, joined together to form a Y. Three phases of alternating current are generated.
21 Voltage RegulatorAlternator output is controlled (regulated) with a solid-state voltage regulator.Senses the alternator voltage output and controls the field current to keep this voltage within the desired range.Circuit Breakers are current sensitive devices, not voltage sensitive, so they provide no protection against high voltages.
27 Circuit Control Devices Protective DevicesFusesCircuit breakersThermal breakersMagnetic breakers
28 Circuit Control Devices Circuit BreakersWill automatically open the circuit if the current becomes excessive.May be reset by moving the operating control.If a fault such as a short circuit exist the breaker will trip again, and should be left open.Trip-free type.
30 Circuit Control Devices ResistorsInserted into circuits to drop voltage by converting some of the electrical energy into heat.FixedVariable
31 Circuit Control Devices InductorsInduced current back flow as the current induced magnetic field collapses when DC current is shut off, causing switch contact arcing.Create magnetic fields for relays.
32 Circuit Control Devices Capacitor is a device which will store an electrical charge (electrons).Quick use: strobe flashCan also be used to limit the amount of electrons flowing in the circuit (an opening switch that is arcing).
33 Circuit Control Devices TransformerPermits voltage of AC current to be increased or decreased.RectifierConverts AC into DC.InverterConverts DC into AC.