Lesson 9: Electrical Components

Batteries

• A 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.

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.

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.

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.

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.

Batteries

• Rated capacity

• Indicates the battery’s ability to perform when it is new.

What determines the battery’s actual capacity?

Batteries

• Actual capacity depends on:

• Battery temperature

• Battery state of charge

• Battery condition

Generators

AC Generator

AC Generator

DC Generator

DC Generator

DC Generator

DC Generator

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.

DC Alternators

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.

DC Alternators

• Advantages

• The load current is generated in the stator or stationary winding and does not have to flow through brushes.

DC Alternators

• The coils in the stator are connected as three windings, joined together to form a Y. Three phases of alternating current are generated.

Voltage Regulator

• Alternator 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.

Circuit Control Devices

Circuit Control Devices

• Control Devices

• Switches

– Toggle–Rocker–Wafer–Relay/Solenoids

Relay Solenoid

Circuit Control Devices

• Protective Devices

• Fuses • Circuit breakers

– Thermal breakers–Magnetic breakers

Circuit Control Devices

• Circuit Breakers

• Will 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.

Circuit Control Devices

• Resistors

• Inserted into circuits to drop voltage by converting some of the electrical energy into heat.

• Fixed

• Variable

Circuit Control Devices

• Inductors

• Induced 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.

Circuit Control Devices

• Capacitor is a device which will store an electrical charge (electrons).

• Quick use: strobe flash

• Can also be used to limit the amount of electrons flowing in the circuit (an opening switch that is arcing).

Circuit Control Devices

• Transformer

• Permits voltage of AC current to be increased or decreased.

• Rectifier

• Converts AC into DC.

• Inverter

• Converts DC into AC.