Definition
The application of direct current to the field windings of a generator or alternator to produce the magnetic field required for electrical output. The strength of the field current controls the voltage produced by the machine.
Plain English
Sending a small electric current through coils inside a generator or alternator to create the magnetism it needs to make electricity. More current to those coils means a stronger magnet, which means more voltage out.
Context Anchor
Seen in aircraft electrical system discussions, especially when describing generators, alternators, voltage regulators, and charging-system faults.
Derivation
From Latin excitare, meaning 'to rouse' or 'stir into action.' The field is 'excited' in the sense of being stirred into producing a magnetic field — without that current, the windings sit inert and no electricity is generated.
Why Pilots Care
Without adequate field excitation the aircraft generator or alternator cannot produce electrical power, risking loss of avionics, lights, and instruments.
Analogy
It is like turning on an electromagnet. Until current flows through the winding, the magnetic field is not strong enough to do the work.
Intuition Check
Field does not mean an airport or open land here; it means a magnetic field. Excitation does not mean emotion; it means energizing an electrical part with current.
Example Sentence 1
When the alternator failed, the pilot suspected a loss of field excitation and reset the field circuit breaker.
Example Sentence 2
During preflight the pilot noted that the ammeter showed proper charging only after field excitation was confirmed.