Definition
The distortion of the main magnetic field in a generator or motor caused by the magnetic field produced by current flowing through the armature windings. As load increases, this opposing field shifts the neutral plane and weakens the main field, reducing output voltage and potentially causing arcing at the brushes if not compensated for.
Plain English
When current flows through the spinning part of a generator, it creates its own magnetic field that pushes against the generator's main magnetic field. This pushback distorts and weakens the main field, which can hurt the generator's output and cause sparking at the brushes.
Context Anchor
Seen in aircraft electrical-system discussions, especially when studying DC generators, starter-generators, brushes, and generator load problems.
Derivation
Armature comes from the Latin armatura, meaning 'armor' or 'equipment.' In electrical machines it refers to the rotating wound part that carries the working current. 'Reaction' here means the opposing magnetic effect this current produces — the armature's own field reacts against the field that drives it.
Why Pilots Care
It reduces generator output and efficiency, requiring design features like interpoles or compensating windings to maintain stable aircraft electrical power.
Grounding Statement
As electrical load increases, the armature’s own magnetic field becomes stronger and can disturb the magnetic field the generator or motor depends on.
Intuition Check
Armature reaction does not mean a pilot’s reaction or a moving part reacting mechanically. It means an electrical and magnetic effect inside a generator or motor.
Example Sentence 1
Compensating windings were added to the generator to offset armature reaction at high electrical loads.
Example Sentence 2
Modern aircraft generators use compensating windings to counteract armature reaction and keep power steady.