Generators, Alternators and Motors

Generators convert mechanical motion into electricity and motors convert it back. Direct-current generators use a commutator and brushes, which are wear items to inspect at every scheduled check. Alternators generate alternating current with stationary windings and a rotating field, rectify it for the direct-current aircraft systems, and are lighter and more reliable, which is why they replaced most direct-current generators.

A regulator holds bus voltage steady regardless of engine speed. Starter-generators crank the engine and then generate in flight. Inverters convert direct current to alternating current for instruments and other alternating-current loads. Batteries support starting and emergency loads rather than normal operation.

Recognise the symptoms first: low bus voltage, voltage flicker, a hot smell, brush dust, or a tripped generator control unit. Then check in order — drive belt or gearbox, cooling airflow path, terminal tightness and corrosion, and grounding — before condemning the unit. Observe polarity and current limits whenever a unit is tested or removed.