Basic operation of an aircraft electrical system
KW meter measures work performed
KVAR meter measures how hard the generator is working.
Methods of producing electricity in aircraft
Generators are rate in amperes at rated voltage. Convert mechanical energy into electrical energy by electromagnetic induction. AC gen. in KVA.
A reverse-current relay disconnects gen. from bus when gen. voltage is less than Battery voltage. Relays are electrical switches used for remote control of circuits.
A carbon-pile-type voltage regulator uses variable resistance to control DC generator current.
Diode is a two-element device that allows current to travel in one direction.
Starter-generator unit combines both systems in turbine aircraft.
Inverters convert DC to 115 volt AC power
Transformer Rectifier Units (TRUs) convert AC to 28 volt DC power. The transformer can change the voltage.
AC Generator Control Units (GCUs) provide generator field controls and indication and protective functions, open phase, under-excitation, and over-voltage.
If a AC generator is being driven but there is no field excitation, residual voltage will be produced.
Generating systems are operated in parallel to obtain equal loads, a paralleling or equalizing circuit distributes the load equally.
Function of aircraft electrical components:
Batteries: two 12 volt batts in series will be 24 volt system.
Lead-acid batt: sulfuric acid and water.
Nickel-cadmium (NICAD) batt: potassium hydroxide and water.
Thermal Runaway is continuous rising current and battery temperature.
A purpose of a electric relay (magnetically operated switch) is to control high-current equipment items with a small switch.
A solenoid is an electromagnetic switch with a movable core.
Soldered terminals are considered unsat for aircraft.
Circuit Breakers:
Electromagnetic-type may be reset immediately and rated in amperes Only trip-free circuit breakers (impossible to hold manually closed) are used in aircraft. Automatic-reset breakers are not used.
The purpose of a fuse-type current limiter is to permit short periods of overload before the fuse link melts.
Aircraft electrical distribution system
The advantage of the parallel bus system is electrical load is automatically redistributed when one generator fails. Bus tie provides a means of isolating a power bus from one that has failed.
Electrical bonding is process of connecting various parts of the aircraft to prevent static electricity discharges within the aircraft structure. Also to decrease the probability of lightning damage to control hinges.
Static dischargers (wicks) dissipate static charges from control surfaces into the air to prevent radio interference.
Generators are rate in amperes at rated voltage. Convert mechanical energy into electrical energy by electromagnetic induction. AC gen. in KVA.
A reverse-current relay disconnects gen. from bus when gen. voltage is less than Battery voltage. Relays are electrical switches used for remote control of circuits.
A carbon-pile-type voltage regulator uses variable resistance to control DC generator current.
Diode is a two-element device that allows current to travel in one direction.
Starter-generator unit combines both systems in turbine aircraft.
Inverters convert DC to 115 volt AC power
Transformer Rectifier Units (TRUs) convert AC to 28 volt DC power. The transformer can change the voltage.
AC Generator Control Units (GCUs) provide generator field controls and indication and protective functions, open phase, under-excitation, and over-voltage.
If a AC generator is being driven but there is no field excitation, residual voltage will be produced.
Generating systems are operated in parallel to obtain equal loads, a paralleling or equalizing circuit distributes the load equally.
Function of aircraft electrical components:
Batteries: two 12 volt batts in series will be 24 volt system.
Lead-acid batt: sulfuric acid and water.
Nickel-cadmium (NICAD) batt: potassium hydroxide and water.
Thermal Runaway is continuous rising current and battery temperature.
A purpose of a electric relay (magnetically operated switch) is to control high-current equipment items with a small switch.
A solenoid is an electromagnetic switch with a movable core.
Soldered terminals are considered unsat for aircraft.
Circuit Breakers:
Electromagnetic-type may be reset immediately and rated in amperes Only trip-free circuit breakers (impossible to hold manually closed) are used in aircraft. Automatic-reset breakers are not used.
The purpose of a fuse-type current limiter is to permit short periods of overload before the fuse link melts.
Aircraft electrical distribution system
The advantage of the parallel bus system is electrical load is automatically redistributed when one generator fails. Bus tie provides a means of isolating a power bus from one that has failed.
Electrical bonding is process of connecting various parts of the aircraft to prevent static electricity discharges within the aircraft structure. Also to decrease the probability of lightning damage to control hinges.
Static dischargers (wicks) dissipate static charges from control surfaces into the air to prevent radio interference.
