Definition
A small auxiliary pole placed between the main field poles of a DC generator or motor, wound and connected so that it produces a magnetic field that cancels the distortion (armature reaction) caused by current flowing in the armature. Its purpose is to ensure clean commutation — the smooth transfer of current between commutator segments — by reducing or eliminating sparking at the brushes.
Plain English
An extra small magnet built into a DC generator or motor, sitting between the main magnets, that stops the brushes from sparking as the machine runs.
Context Anchor
Seen in aircraft electrical-system maintenance when studying DC generators, starters, and motor-generator units.
Derivation
From the Latin 'inter' meaning 'between' and 'pole' meaning a magnetic pole. So an interpole is literally a pole placed between the main poles. The name describes exactly where it sits.
Why Pilots Care
Brush sparking wears out brushes and commutators quickly and can produce electrical noise that interferes with radios and avionics. Interpoles keep DC generators and motors running cleanly and reliably, which matters on aircraft that still rely on DC machinery for charging or starting.
Intuition Check
An interpole is not one of the main magnetic poles. It is a smaller helper pole placed between the main poles to make current switching smoother.
Example Sentence 1
When troubleshooting heavy brush sparking in the DC generator, the technician checked the interpole windings for a possible open circuit.
Example Sentence 2
During engine start, the starter-generator relies on its interpoles to maintain clean commutation under high current load.