FAA Aviation Mechanic Airframe (AMA)Airframe Electrical and InstrumentsMedium
A brushless AC alternator on a modern aircraft must supply direct current to charge the battery and power the DC bus. Which component converts the alternator's three-phase AC output into DC before it reaches the bus?
- AVoltage regulator
- BInverter
- CCommutator
- DRectifier (diode assembly)
Show answer & explanationAnswer & explanation
Correct answer: D. Rectifier (diode assembly)
A rectifier, typically a set of diodes, converts the alternator's AC output into DC. The voltage regulator controls the output level, but does not perform AC-to-DC conversion; a commutator is used on brush-type DC generators, not brushless alternators.
Why the other options are wrong
- A. Regulates voltage output but does not convert AC to DC.
- B. An inverter does the opposite, converting DC to AC.
- C. Commutators are mechanical devices used in brush-type DC generators, not brushless alternators.
Rectifier
A device, typically using diodes, that converts alternating current (AC) into direct current (DC) in an aircraft alternator system.
- Uses diodes that allow current flow in only one direction
- Found in brushless AC alternator systems
- Different from an inverter, which converts DC to AC
Memory trick: Rectifier = one-way valve for electrons